CPT based foundation engineering

D-Foundations

User Manual
D-F OUNDATIONS

CPT based foundation engineering

User Manual

Version: 23.1
SVN Revision: 00

23 February 2023
D-F OUNDATIONS, User Manual

Published and printed by:

Deltares telephone: +31 88 335 82 73
Boussinesqweg 1 e-mail: info@deltares.nl
2629 HV Delft www: https://www.deltares.nl
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The Netherlands

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Copyright © 2023 Deltares

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print, photo copy, microfilm or any other means, without written permission from the publisher:
Deltares.
 Contents

Contents
List of Tables ix

List of Figures xi

1 General Information 1
1.1 Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2.1 Overview of options . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.3 Limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.4 Minimum System Requirements . . . . . . . . . . . . . . . . . . . . . . . 2
1.5 History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.6 Definitions and Symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.7 Getting Help . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.8 Getting Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.9 Deltares . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
1.10 Deltares Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
1.11 On-line software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

2 Getting Started 13
2.1 Starting D-F OUNDATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.2 Main Window . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.2.1 Menu bar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.2.2 Icon bar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.2.3 Tree view . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.2.4 Title panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
2.2.5 Status bar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
2.3 Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
2.4 Tips and Tricks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
2.4.1 Keyboard shortcuts . . . . . . . . . . . . . . . . . . . . . . . . . . 18
2.4.2 Exporting figures and reports . . . . . . . . . . . . . . . . . . . . . 18
2.4.3 Copying part of a table . . . . . . . . . . . . . . . . . . . . . . . . 19

3 General 21
3.1 File menu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
3.2 Tools menu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
3.2.1 Program Options . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
3.2.2 CPT interpretation model . . . . . . . . . . . . . . . . . . . . . . . 27
3.3 Help menu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
3.3.1 Manual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
3.3.2 Verification Report . . . . . . . . . . . . . . . . . . . . . . . . . . 28
3.3.3 Log Messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
3.3.4 Deltares Software Website . . . . . . . . . . . . . . . . . . . . . . 29
3.3.5 Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
3.3.6 About . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
3.4 Project menu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
3.4.1 Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
3.4.2 Project Properties . . . . . . . . . . . . . . . . . . . . . . . . . . 30
3.4.3 Location Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
3.4.4 View Input File . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
3.5 Project Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
3.6 Batch Calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

4 Bearing Piles (EC7-NL) – Input & Calculations 37

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4.1 Tree view . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

4.2 Construction Sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
4.3 Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
4.3.1 Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
4.3.1.1 Materials – Add from ‘Standard’ . . . . . . . . . . . . . . 40
4.3.1.2 Materials – Add manually . . . . . . . . . . . . . . . . . . 41
4.3.1.3 Materials – Match Material . . . . . . . . . . . . . . . . . 41
4.3.2 Profiles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
4.3.2.1 Adding Profiles . . . . . . . . . . . . . . . . . . . . . . . 42
4.3.2.2 Options for existing profiles . . . . . . . . . . . . . . . . . 44
4.3.2.3 Editing Layers . . . . . . . . . . . . . . . . . . . . . . . 45
4.3.2.4 Additional Data . . . . . . . . . . . . . . . . . . . . . . . 47
4.3.2.5 Viewing Profiles . . . . . . . . . . . . . . . . . . . . . . 49
4.3.2.6 Summary Pressures . . . . . . . . . . . . . . . . . . . . 51
4.4 Foundation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
4.4.1 Pile Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
4.4.2 Pile Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
4.4.3 Top View Foundation . . . . . . . . . . . . . . . . . . . . . . . . . 59
4.5 Excavation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
4.6 Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
4.6.1 Options for a Bearing Piles (EC7-NL) calculation . . . . . . . . . . . 64
4.6.2 Preliminary Design for Bearing Piles (EC7-NL) . . . . . . . . . . . . 67
4.6.2.1 Preliminary design: Indication bearing capacity . . . . . . . 69
4.6.2.2 Preliminary design: Bearing capacity at fixed pile tip levels . 70
4.6.2.3 Preliminary design: Pile tip levels and net bearing capacity . 70
4.6.3 Verification for Bearing Piles (EC7-NL) . . . . . . . . . . . . . . . . 71
4.6.3.1 Verification: Design . . . . . . . . . . . . . . . . . . . . . 72
4.6.3.2 Verification: Complete . . . . . . . . . . . . . . . . . . . 73

5 Tension Piles (EC7-NL) – Input & Calculations 75

5.1 Tree view . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
5.2 Construction Sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
5.3 Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
5.3.1 Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
5.3.1.1 Materials – Add from ‘Standard’ . . . . . . . . . . . . . . 77
5.3.1.2 Materials – Add manually . . . . . . . . . . . . . . . . . . 78
5.3.1.3 Materials – Match Material . . . . . . . . . . . . . . . . . 79
5.3.2 Profiles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
5.3.2.1 Adding Profiles . . . . . . . . . . . . . . . . . . . . . . . 80
5.3.2.2 Options for existing profiles . . . . . . . . . . . . . . . . . 80
5.3.2.3 Editing Layers . . . . . . . . . . . . . . . . . . . . . . . 80
5.3.2.4 Additional Data . . . . . . . . . . . . . . . . . . . . . . . 83
5.3.2.5 Viewing Profiles . . . . . . . . . . . . . . . . . . . . . . 84
5.3.2.6 Summary Pressures . . . . . . . . . . . . . . . . . . . . 84
5.4 Foundation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
5.4.1 Pile Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
5.4.2 Pile Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
5.4.3 Top View Foundation . . . . . . . . . . . . . . . . . . . . . . . . . 92
5.5 Excavation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
5.6 Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
5.6.1 Options for a Tension Piles calculation . . . . . . . . . . . . . . . . 95
5.6.2 Preliminary Design Tension Piles . . . . . . . . . . . . . . . . . . . 97
5.6.2.1 Preliminary design: Indication bearing capacity . . . . . . . 98
5.6.2.2 Preliminary design: Bearing capacity at fixed pile tip levels . 98

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5.6.2.3 Preliminary design: Pile tip levels and net bearing capacity . 99
5.6.3 Verification Tension Piles . . . . . . . . . . . . . . . . . . . . . . . 99

6 Shallow Foundations (EC7-NL) – Input & Calculations 101

6.1 Tree view . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
6.2 Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
6.2.1 Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
6.2.1.1 Materials – Add from ‘Standard’ . . . . . . . . . . . . . . 103
6.2.1.2 Materials – Add manually . . . . . . . . . . . . . . . . . . 104
6.2.1.3 Materials – Match Material . . . . . . . . . . . . . . . . . 104
6.2.2 Profiles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104
6.2.2.1 Adding Profiles . . . . . . . . . . . . . . . . . . . . . . . 105
6.2.2.2 Options for existing profiles . . . . . . . . . . . . . . . . . 105
6.2.2.3 Editing Layers . . . . . . . . . . . . . . . . . . . . . . . 105
6.2.2.4 Additional Data . . . . . . . . . . . . . . . . . . . . . . . 105
6.2.2.5 Viewing Profiles . . . . . . . . . . . . . . . . . . . . . . 106
6.2.2.6 Summary Pressures . . . . . . . . . . . . . . . . . . . . 106
6.2.3 Slopes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
6.3 Foundation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
6.3.1 Types of Shallow Foundations . . . . . . . . . . . . . . . . . . . . 108
6.3.2 Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
6.3.3 Foundation plan . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
6.3.4 Top View Foundation . . . . . . . . . . . . . . . . . . . . . . . . . 111
6.4 Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112
6.4.1 Options for a Shallow Foundations calculation . . . . . . . . . . . . 113
6.4.2 Calculation options . . . . . . . . . . . . . . . . . . . . . . . . . . 114
6.4.2.1 Optimize Dimensions . . . . . . . . . . . . . . . . . . . . 115
6.4.2.2 Maximize Vertical Loads . . . . . . . . . . . . . . . . . . 116
6.4.2.3 Verification . . . . . . . . . . . . . . . . . . . . . . . . . 117

7 View Results 119

7.1 Load-Settlement Curve/Load-Rise Curve . . . . . . . . . . . . . . . . . . . 119
7.2 Design Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
7.3 Intermediate Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
7.3.1 Intermediate Results for Bearing Piles (EC7-NL) . . . . . . . . . . . 122
7.3.1.1 Limit state EQU (calculation per CPT) . . . . . . . . . . . 123
7.3.1.2 Limit state GEO and serviceability limit state (calculation for
each CPT for each pile) . . . . . . . . . . . . . . . . . . 124
7.3.2 Intermediate Results for Shallow Foundations (EC7-NL) . . . . . . . 125
7.3.2.1 Limit state EQU . . . . . . . . . . . . . . . . . . . . . . 125
7.3.2.2 Limit states GEO and serviceability limit state . . . . . . . 129
7.4 Report and report content selection . . . . . . . . . . . . . . . . . . . . . . 132
7.4.1 Report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132
7.4.2 Report Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132
7.4.3 Report content selection . . . . . . . . . . . . . . . . . . . . . . . 133

8 Tutorial 1: Preliminary Design of Bearing Piles for a Storehouse 135

8.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135
8.2 Setting up a new project . . . . . . . . . . . . . . . . . . . . . . . . . . . 136
8.3 Construction sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136
8.4 Creating soil profiles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137
8.5 Defining the foundation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140
8.6 Entering the context . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142
8.7 Making a preliminary design . . . . . . . . . . . . . . . . . . . . . . . . . 143

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8.8 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145

8.9 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146

9 Tutorial 2: Obsolete (Previously: Feasibility of Bearing Piles for a Storehouse) 147

10 Tutorial 3: Verification of Bearing Piles for a Storehouse 149

10.1 Introduction to the case . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149
10.2 Preparing a new project . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150
10.3 Defining the correct pile tip level(s) . . . . . . . . . . . . . . . . . . . . . . 150
10.4 Defining the pile plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150
10.5 Starting the calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152
10.6 Evaluating the results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153
10.7 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154

11 Tutorial 4: Pipeline Duct on Bearing Piles 155

11.1 Introduction to the case . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155
11.2 Project input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156
11.3 Preliminary Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157
11.4 Verification of the design . . . . . . . . . . . . . . . . . . . . . . . . . . . 158
11.5 Maximum negative skin friction . . . . . . . . . . . . . . . . . . . . . . . . 161
11.6 Using continuous flight auger piles . . . . . . . . . . . . . . . . . . . . . . 163
11.7 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164

12 Tutorial 5: Preliminary Design of Tension Piles for a Parking Garage 165

12.1 Introduction to the case . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165
12.2 Entering the project data . . . . . . . . . . . . . . . . . . . . . . . . . . . 166
12.2.1 Soil profile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166
12.2.2 Foundation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170
12.2.3 Excavation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171
12.3 Calculation and results . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172
12.4 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176

13 Tutorial 6: Farm with a Pond (Shallow Foundations) 177

13.1 Introduction to the case . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177
13.2 Entering the project data . . . . . . . . . . . . . . . . . . . . . . . . . . . 178
13.3 Verification of the design . . . . . . . . . . . . . . . . . . . . . . . . . . . 181
13.4 Influence of the fishing pond . . . . . . . . . . . . . . . . . . . . . . . . . 184
13.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186

14 Tutorial 7: Obsolete (Previously: Design of Bearing Piles using the Belgian

method) 187

15 Tutorial 8: Verification of Tension Piles for a Parking Garage 189

15.1 Introduction to the case . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189
15.2 Preparing a new project . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189
15.3 Entering the project data . . . . . . . . . . . . . . . . . . . . . . . . . . . 189
15.3.1 Soil Profile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189
15.3.2 Pile Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191
15.4 Starting the calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191
15.5 Evaluating the results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192
15.6 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193

16 Bearing Piles model (EC7-NL) 195

16.1 Area of application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195
16.2 Limit states . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195

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16.3 Calculation process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195

16.3.1 Verifying limit state STR . . . . . . . . . . . . . . . . . . . . . . . 195
16.3.2 Verifying limit state GEO and serviceability limit state . . . . . . . . . 196
16.4 Geometric problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196
16.5 Problems in interpreting standards . . . . . . . . . . . . . . . . . . . . . . 197
16.6 Units, dimensions and drawing agreements . . . . . . . . . . . . . . . . . . 200
16.7 Bearing Piles schematics . . . . . . . . . . . . . . . . . . . . . . . . . . . 202
16.7.1 Problem boundaries . . . . . . . . . . . . . . . . . . . . . . . . . 202
16.7.2 Variation in the level of the bearing layer . . . . . . . . . . . . . . . 203
16.7.3 Skin friction zones . . . . . . . . . . . . . . . . . . . . . . . . . . 203
16.7.4 Non-rigid/rigid . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205
16.7.5 Combination of superimposed load/excavation . . . . . . . . . . . . 205
16.7.6 Merging sub-calculations . . . . . . . . . . . . . . . . . . . . . . . 206

17 Tension Piles model (EC7-NL) 207

17.1 Area of application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207
17.2 Design of tension piles according to EC7-NL (NEN 9997-1+C2:2017) . . . . . 207
17.3 The Netherlands Eurocode 7 (EC7-NL) . . . . . . . . . . . . . . . . . . . . 208
17.4 Verifying displacements of Tension Piles . . . . . . . . . . . . . . . . . . . 208
17.5 Calculating the bearing capacity of a tension pile . . . . . . . . . . . . . . . 208
17.5.1 Step 1: Reduction of the cone resistance due to overconsolidation . . 209
17.5.2 Step 2: Reduction of cone resistance due to excavation . . . . . . . . 209
17.5.3 Step 3: Determination of the design value of the cone resistance (in-
cluding safety factors) . . . . . . . . . . . . . . . . . . . . . . . . . 211
17.5.4 Step 4: Determination of factor f1 (effect of installation) . . . . . . . . 211
17.5.5 Step 5: Determination of factor f2 (effect of reduction of stresses due
to tension forces in pile groups) . . . . . . . . . . . . . . . . . . . . 213
17.5.6 Step 6: Determination of the maximum tension capacity Rt;d . . . . . 214
17.5.7 Step 7: Determination of the total soil weight Rt;kluit;d . . . . . . . . 214
17.5.8 Step 8: Addition of the pile weight . . . . . . . . . . . . . . . . . . . 215
17.6 Problems in interpreting standards . . . . . . . . . . . . . . . . . . . . . . 216
17.7 Units, dimensions and drawing agreements . . . . . . . . . . . . . . . . . . 216
17.8 Tension Piles schematics . . . . . . . . . . . . . . . . . . . . . . . . . . . 218
17.8.1 Problem boundaries . . . . . . . . . . . . . . . . . . . . . . . . . 219
17.8.2 Variation in the pile tip level . . . . . . . . . . . . . . . . . . . . . . 219
17.8.3 Skin friction zone . . . . . . . . . . . . . . . . . . . . . . . . . . . 219
17.8.4 Non-rigid/rigid . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220
17.8.5 Combination of superimposed load and excavation . . . . . . . . . . 220

18 Shallow Foundations model (EC7-NL) 223

18.1 Area of application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223
18.2 Limit states . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223
18.3 Calculation process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223
18.3.1 Verifying limit state STR . . . . . . . . . . . . . . . . . . . . . . . 223
18.3.2 Verifying limit state GEO and serviceability limit state . . . . . . . . . 224
18.4 Geometric problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225
18.5 Units, dimensions and drawing agreements . . . . . . . . . . . . . . . . . . 226
18.6 Shallow Foundations schematics . . . . . . . . . . . . . . . . . . . . . . . 228
18.6.1 Problem boundaries . . . . . . . . . . . . . . . . . . . . . . . . . 229
18.6.2 Variation in the level of the bearing layer . . . . . . . . . . . . . . . 229
18.6.3 Non-rigid/rigid . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229
18.6.4 Merging sub-calculations . . . . . . . . . . . . . . . . . . . . . . . 229

19 Benchmarks 231

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20 Literature 233

viii Deltares
 List of Tables

List of Tables
2.1 Keyboard shortcuts for D-F OUNDATIONS . . . . . . . . . . . . . . . . . . . 18

7.1 Overview of the displayed design results . . . . . . . . . . . . . . . . . . . 121

11.1 Pile tip levels resulting from the preliminary design . . . . . . . . . . . . . . 158

12.1 Characteristic values of soil parameters based on boring . . . . . . . . . . . 166

13.1 Soil profile near to the farmhouse . . . . . . . . . . . . . . . . . . . . . . . 178

16.1 Units of the input/output parameters . . . . . . . . . . . . . . . . . . . . . . 201

16.2 Limits applied to the maximum problem size . . . . . . . . . . . . . . . . . 202

17.1 Units of the input/output parameters . . . . . . . . . . . . . . . . . . . . . . 218

17.2 Limits applied to the maximum problem size . . . . . . . . . . . . . . . . . 219

18.1 Units of the input/output parameters . . . . . . . . . . . . . . . . . . . . . . 227

18.2 Limits applied to the maximum problem size . . . . . . . . . . . . . . . . . 229

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x Deltares
 List of Figures

List of Figures
1.1 Deltares website for this software . . . . . . . . . . . . . . . . . . . . . . . 10
1.2 Support window, Problem Description tab . . . . . . . . . . . . . . . . . . . 11

2.1 D-F OUNDATIONS main window . . . . . . . . . . . . . . . . . . . . . . . . 13

2.2 D-F OUNDATIONS menu bar . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.3 D-F OUNDATIONS icon bar . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.4 D-F OUNDATIONS tree view when no project is opened . . . . . . . . . . . . . 15
2.5 Tree view when a (Bearing Piles EC7-NL) project is opened . . . . . . . . . . 15
2.6 The tree view may be manipulated using pop-up menus . . . . . . . . . . . . 16
2.7 Title panel and Status bar at the bottom of the main window . . . . . . . . . 16
2.8 Selection of different parts of a table using the arrow cursor . . . . . . . . . . 19

3.1 Export Report window . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

3.2 Export Options window . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
3.3 Program Options window, View tab . . . . . . . . . . . . . . . . . . . . . . 23
3.4 Program Options window, General tab . . . . . . . . . . . . . . . . . . . . 23
3.5 Program Options window, Locations tab . . . . . . . . . . . . . . . . . . . . 24
3.6 Program Options window, Language tab . . . . . . . . . . . . . . . . . . . 25
3.7 Program Options window, License tab . . . . . . . . . . . . . . . . . . . . 26
3.8 Program Options window, CPT Interpretation tab . . . . . . . . . . . . . . . 26
3.9 CPT Interpretation Model window . . . . . . . . . . . . . . . . . . . . . . . 28
3.10 Log Messages window . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
3.11 Model window . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
3.12 Project Properties window, Top View Foundation tab . . . . . . . . . . . . . 31
3.13 Project Properties window, Load Settlement Curve tab . . . . . . . . . . . . 31
3.14 Project Properties window, View CPT/Profile tab . . . . . . . . . . . . . . . 32
3.15 Location Map window . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
3.16 Top View Foundation window showing the location map as background picture 33
3.17 Project Properties – Description window . . . . . . . . . . . . . . . . . . . 34
3.18 Run window . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
3.19 Start Batch Processing window . . . . . . . . . . . . . . . . . . . . . . . . 35
3.20 Batch Processing Progress window . . . . . . . . . . . . . . . . . . . . . . 36

4.1 Main window for the Bearing Piles (EC7-NL) model . . . . . . . . . . . . . . 37

4.2 Construction Sequence window for the Bearing Piles (EC7-NL) model . . . . 39
4.3 Soil – Materials window for Bearing Piles (EC7-NL) model . . . . . . . . . . 39
4.4 NEN 9997-1 Table 2.b (Table 2.b of NEN 9997-1+C2:2017) window for Bearing
Piles (EC7-NL) model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
4.5 Match Material window . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
4.6 Import CPTs from file window . . . . . . . . . . . . . . . . . . . . . . . . . 43
4.7 Soil – Profiles – New CPT window showing ‘empty’ profile . . . . . . . . . . 44
4.8 Soil / Profiles node, menu . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
4.9 Edit CPT Values window . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
4.10 Soil – Profiles window, Layers tab . . . . . . . . . . . . . . . . . . . . . . . 46
4.11 Soil – Profiles window, Additional Data tab for Bearing Piles (EC7-NL) model . 47
4.12 Soil – Profiles window, Additional Data tab . . . . . . . . . . . . . . . . . . 50
4.13 Soil – Profiles window, Summary Pressures tab . . . . . . . . . . . . . . . . 51
4.14 Foundation – Pile Types window for Bearing Piles (EC7-NL) model . . . . . . 52
4.15 Foundation – Pile Properties window for Bearing Piles (EC7-NL) model . . . . 56
4.16 Pile Grid window for Bearing Piles (EC7-NL) model . . . . . . . . . . . . . . 58
4.17 Edit properties for all positions window for Bearing Piles (EC7-NL) model . . . 59
4.18 Foundation – Top View Foundation window for Bearing Piles (EC7-NL) model . 59
4.19 Excavation window . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

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4.20 Excavation window, pop menu for viewing reduced values . . . . . . . . . . . 62

4.21 Reduced CPT values table . . . . . . . . . . . . . . . . . . . . . . . . . . 63
4.22 Calculation window for Bearing Piles (EC7-NL) model . . . . . . . . . . . . . 64
4.23 Calculation window, Options for Bearing Piles (EC7-NL) model . . . . . . . . 64
4.24 Calculation window, Preliminary Design for Bearing Piles (EC7-NL) model . . 68
4.25 Schematization of the Begemann reduction of cone resistance for a Verifica-
tion and a Preliminary Design calculation . . . . . . . . . . . . . . . . . . . 69
4.26 Calculation window, Verification for Bearing Piles (EC7-NL) model . . . . . . 71

5.1 Main window for the Tension Piles (EC7-NL) model . . . . . . . . . . . . . . 75

5.2 Construction Sequence window for the Tension Piles (EC7-NL) model . . . . 76
5.3 Soil – Materials window for Tension Piles (EC7-NL) model . . . . . . . . . . 77
5.4 NEN 9997-1 Table 2.b window for Tension Piles (EC7-NL) model . . . . . . . 78
5.5 Soil – Profiles window, Layers tab . . . . . . . . . . . . . . . . . . . . . . . 81
5.6 Soil – Profiles window for Tension Piles (EC7-NL) model, Pore Pressure and
OCR tab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
5.7 Soil – Profiles window, Additional Data tab . . . . . . . . . . . . . . . . . . 83
5.8 Soil – Profiles window, Additional Data tab . . . . . . . . . . . . . . . . . . 84
5.9 Soil – Profiles window, Summary Pressures tab . . . . . . . . . . . . . . . . 85
5.10 Foundation – Pile Types window for Tension Piles (EC7-NL) model . . . . . . 86
5.11 Foundation – Pile Properties window for Tension Piles (EC7-NL) model . . . . 89
5.12 Pile Grid window for Tension Piles (EC7-NL) model . . . . . . . . . . . . . . 91
5.13 Edit properties for all positions window for Tension Piles (EC7-NL) model . . . 92
5.14 Foundation – Top View Foundation window for Tension Piles (EC7-NL) model . 92
5.15 Excavation window . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
5.16 Calculation window for Tension Piles (EC7-NL) model . . . . . . . . . . . . . 95
5.17 Calculation window for Tension Piles (EC7-NL) model . . . . . . . . . . . . . 95
5.18 Calculation window, Preliminary Design for Tension Piles (EC7-NL) model . . 97
5.19 Calculation window, Verification for Bearing Piles (EC7-NL) model . . . . . . 100

6.1 Main window for the Shallow Foundations (EC7-NL) model . . . . . . . . . . 101
6.2 Soil – Materials window for Shallow Foundations (EC7-NL) model . . . . . . . 102
6.3 NEN 9997-1 Table 2.b window for Shallow Foundations (EC7-NL) model . . . 103
6.4 Soil – Profiles window, Additional Data tab for Shallow Foundations (EC7-NL)
model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
6.5 Soil – Profiles window, Additional Data tab . . . . . . . . . . . . . . . . . . 106
6.6 Soil – Profiles window, Summary Pressures tab . . . . . . . . . . . . . . . . 107
6.7 Soil – Slopes window . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
6.8 Foundation – Types window for Shallow Foundations (EC7-NL) model . . . . 108
6.9 Foundation – Loads window . . . . . . . . . . . . . . . . . . . . . . . . . 109
6.10 Foundation – Foundation Plan window . . . . . . . . . . . . . . . . . . . . 110
6.11 Foundation – Top View Foundation window for Shallow Foundations (EC7-NL)
model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
6.12 Calculation window for Shallow Foundations (EC7-NL) model . . . . . . . . . 112
6.13 Calculation window for Shallow Foundations (EC7-NL) model . . . . . . . . . 113
6.14 Calculation options for the Shallow Foundations (EC7-NL) model . . . . . . . 114
6.15 Calculation window, Options sub-window for an Optimize Dimensions calculation115
6.16 Calculation window, Options sub-window for a Maximize Vertical Loads calcu-
lation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116

7.1 Load / Settlement Curve window Bearing Piles (EC7-NL) . . . . . . . . . . . 119

7.2 Load / Rise Curve window Tension Piles (EC7-NL) . . . . . . . . . . . . . . 120
7.3 Design Results window – Header . . . . . . . . . . . . . . . . . . . . . . . 121
7.4 Design Results window – Header . . . . . . . . . . . . . . . . . . . . . . . 122

xii Deltares
 List of Figures

7.5 Report Options window . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133

7.6 Report Selection window . . . . . . . . . . . . . . . . . . . . . . . . . . . 134

8.1 Storehouse construction in a delta environment (Tutorial 1) . . . . . . . . . . 135

8.2 Project Properties – Description window . . . . . . . . . . . . . . . . . . . 136
8.3 CPT 01 (Tutorial 1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137
8.4 CPT 02 (Tutorial 1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138
8.5 Soil – Profiles window . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139
8.6 Soil – Profiles window, Additional Data tab . . . . . . . . . . . . . . . . . . 140
8.7 Foundation – Pile Types window . . . . . . . . . . . . . . . . . . . . . . . 140
8.8 Creating new pile types . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141
8.9 Foundation – Pile Types window, Selecting dimensions . . . . . . . . . . . . 142
8.10 Foundation – Pile Properties window . . . . . . . . . . . . . . . . . . . . . 143
8.11 Profiles window, Detail of the Soil . . . . . . . . . . . . . . . . . . . . . . . 143
8.12 Calculation window . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144
8.13 Design Results window, Chart tab . . . . . . . . . . . . . . . . . . . . . . 145

10.1 Boring, front and top views of the pile plan (Tutorial 3) . . . . . . . . . . . . . 149
10.2 Pile Grid window . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151
10.3 Top View Foundation window, Overview of the pile plan . . . . . . . . . . . . 151
10.4 Calculation window . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152
10.5 Report window, Results of the Verification of Limit States STR, GEO, and
serviceability limit state (Tutorial-3a) . . . . . . . . . . . . . . . . . . . . . . 153
10.6 Calculation window, Selecting Rigid for the Rigidity of superstructure . . . . . 154
10.7 Report window, Results of the Verification of Limit States STR, GEO, and
serviceability limit state (Tutorial-3b) . . . . . . . . . . . . . . . . . . . . . . 154

11.1 A pipeline duct (Tutorial 4) . . . . . . . . . . . . . . . . . . . . . . . . . . 155

11.2 CPT 01 at the site where the pipeline duct is to be constructed (Tutorial 4) . . 156
11.3 Calculation window, Selection of CPT 1 for calculation (Tutorial 4a) . . . . . . 157
11.4 Design Results window (Tutorial 4a) . . . . . . . . . . . . . . . . . . . . . 158
11.5 Design Results window (Tutorial 4b) . . . . . . . . . . . . . . . . . . . . . 158
11.6 Top View Foundation window, Pile plan of the two supports . . . . . . . . . . 159
11.7 Calculation window, Selection of CPTs and pile type for Verification, Design
calculation(Tutorial 4c) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160
11.8 Design Results window, Text tab (Tutorial 4c) . . . . . . . . . . . . . . . . . 160
11.9 Calculation window, Selection of CPTs and pile type (Tutorial 4d) . . . . . . . 161
11.10 Intermediate Results window (Tutorial 4d) . . . . . . . . . . . . . . . . . . . 162
11.11 Intermediate Results window (Tutorial 4e) . . . . . . . . . . . . . . . . . . . 162
11.12 Foundation – Pile Types window, Adding the continuous flight auger pile (Tu-
torial 4f) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163
11.13 Design Results window, Text tab (Tutorial 4f) . . . . . . . . . . . . . . . . . 164

12.1 Design of a foundation of a parking garage (Tutorial 5) . . . . . . . . . . . . 165

12.2 Model window . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166
12.3 Soil – Profiles window using NEN rule and a minimum layer thickness of 10 m 167
12.4 Soil – Materials window . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168
12.5 Soil – Profiles window, selection of materials for the profile . . . . . . . . . . 169
12.6 Soil – Profiles window, Pore Pressure and OCR tab . . . . . . . . . . . . . . 170
12.7 Soil – Profiles window, Additional Data tab . . . . . . . . . . . . . . . . . . 170
12.8 Foundation – Pile Types window for a rectangular pile . . . . . . . . . . . . . 170
12.9 Pile Grid Tension Piles (EC7-NL) window . . . . . . . . . . . . . . . . . . . 171
12.10 Foundation – Pile Properties window showing input pile grid . . . . . . . . . 171
12.11 Excavation window with Begemann option selected . . . . . . . . . . . . . . 172
12.12 Calculation window for Tension Piles (EC7-NL) model . . . . . . . . . . . . . 173

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12.13 The simplified pile plan of the parking garage . . . . . . . . . . . . . . . . . 173

12.14 Design Results (indicative ξ3 ) window, Text tab . . . . . . . . . . . . . . . . 174
12.15 Design Results (indicative ξ3 ) window, Text tab . . . . . . . . . . . . . . . . 175
12.16 Design Results (indicative ξ3 ) window, Chart tab . . . . . . . . . . . . . . . 175

13.1 Fishing pond near farmhouse (Tutorial 6) . . . . . . . . . . . . . . . . . . . 177

13.2 Soil parameters, changing model warning window . . . . . . . . . . . . . . 178
13.3 Soil – Profiles window, Layers tab . . . . . . . . . . . . . . . . . . . . . . . 179
13.4 Soil – Profiles window, Additional Data tab for Shallow Foundations model . . 179
13.5 Foundation – Types window . . . . . . . . . . . . . . . . . . . . . . . . . . 180
13.6 Foundation - Loads window . . . . . . . . . . . . . . . . . . . . . . . . . . 181
13.7 Foundation Plan window . . . . . . . . . . . . . . . . . . . . . . . . . . . 181
13.8 Calculation window with default deformation demands conform to EC7-NL
(NEN 9997-1+C2:2017) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182
13.9 Report window, Results of the Verification of Limit State EQU . . . . . . . . . 183
13.10 Report window, Results of the Verification of Serviceability Limit State . . . . 183
13.11 Report window, Results of the Verification of Limit State STR/GEO . . . . . . 184
13.12 Soil – Slopes window . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184
13.13 Foundation Plan window . . . . . . . . . . . . . . . . . . . . . . . . . . . 185
13.14 Report window, Results for Limit State EQU with and without the pond . . . . 185
13.15 Report window, Results for Limit State EQU without pond and with two differ-
ent ponds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186

15.1 Soil Profile window, Layers tab for CPT 02 after interpretation . . . . . . . . . 190
15.2 Soil Profile window, Layers tab for CPT 02 after modification . . . . . . . . . 191
15.3 Calculation window . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192
15.4 Report window, Results of the Verification of Limit States EQU, STR/GEO and
serviceability limit state . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193

16.1 Gap in skin friction zone . . . . . . . . . . . . . . . . . . . . . . . . . . . 200

16.2 Sign conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201
16.3 Skin friction levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204
16.4 Two different partial calculations required due to mixed rigidity of structure . . 205
16.5 Splitting a problem into parts due to a combination of excavation and super
imposed loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206

17.1 Determination of the change in effective stresses due to the excavation . . . . 210
17.2 Pulled out soil geometry . . . . . . . . . . . . . . . . . . . . . . . . . . . 214
17.3 Sign conventions for settlements . . . . . . . . . . . . . . . . . . . . . . . 217
17.4 Partial calculations for a mixed rigidity structure . . . . . . . . . . . . . . . . 220

18.1 Finding Aef . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224

18.2 Slope adjustment for punch . . . . . . . . . . . . . . . . . . . . . . . . . . 226
18.3 Sign conventions for settlements . . . . . . . . . . . . . . . . . . . . . . . 227

xiv Deltares
 1 General Information

1.1 Preface
The application of Eurocode 7 for foundation design and practice in the Netherlands has
been implemented in the newest Dutch standard (NEN): NEN 9997-1+C2:2017. In reacting
to this, D-F OUNDATIONS enables the user to calculate piles (bearing and tension) and shallow
foundation in accordance with the Netherlands Eurocode 7 (EC7-NL). There are several doc-
uments that have been included on composing the Netherlands Eurocode 7 in Dutch standard
NEN 9997-1, they are: NEN-EN 1997-1 (Eurocode 7-1), NEN-EN 1997-1/NB (Nationale bi-
jlage bij Eurocode 7-1), and NEN 9097-1 (Aanvullende bepalingen voor het geotechnische
ontwerp).

D-F OUNDATIONS graphical interactive interface requires just a short training period, allowing
users to focus their skills directly on the input of sound geotechnical data and on the subse-
quent design.

D-F OUNDATIONS comprehensive range of calculation options means it can be used to produce
preliminary advice, to optimize designs and to verify full scale designs. The ability to overrule
and redefine various design code parameters allows D-F OUNDATIONS to be used by engineers
to perform standard types of design and verification operations (i.e. calculations based entirely
on standards and guidelines) as well as specialized calculations using user-defined foundation
types and factors.

1.2 Features
D-F OUNDATIONS is a powerful tool, incorporating the following features:

⋄ Comprehensive coverage D-F OUNDATIONS uses the Netherlands Eurocode (EC7-NL)

for accurate design of vertically loaded bearing piles and tension piles and shallow
foundations with both horizontal and vertical loading.
⋄ Easy soil data definition Importing CPT data is possible in several formats, includ-
ing the Geotechnical Exchange Format (GEF). The automatic CPT interpretation tool
provides soil-type dependent proposals, including all additional parameters.
⋄ Fast design of pile plans D-F OUNDATIONS gives simultaneous indication of capacity
and required length for different pile types and different soil conditions.
⋄ Pile group interaction In calculations, the effect of pile group interaction on settlement
is included as well as on bearing capacity for the selected pile type and pile plan.
⋄ Fast design of shallow foundations Foundation dimensions can be optimized. Also
the required width for strip foundations and the capacity and stability of shallow founda-
tions can be checked.
⋄ Code-based verification A complete verification report can be generated, including all
steps performed during calculation. Intermediate results are available in a separate file.
⋄ Standard parameters All standard parameters provided by NEN (such as soil parame-
ters as provided by table 2.b of NEN 9997-1+C2:2017 (NEN, 2017) as well as pile type
parameters) are incorporated within D-F OUNDATIONS for easy and fast selection.

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1.2.1 Overview of options

The following is an overview of the options available in D-F OUNDATIONS:

⋄ Design and verification of bearing piles according to the Dutch Eurocode 7 (EC7-NL)
implemented in NEN 9997-1+C2:2017 (NEN, 2017).
⋄ Design of tension piles according to the Dutch Eurocode 7 (EC7-NL) implemented in
NEN 9997-1+C2:2017 (NEN, 2017).
⋄ Design and verification of shallow foundations according to the Dutch Eurocode 7 (EC7-
NL) implemented in NEN 9997-1+C2:2017 (NEN, 2017).

All the above options include several expert options to perform calculations beyond the guide-
lines. For example, it is possible to define pile types not covered in these standards and
guidelines, and to overrule several factors normally determined according to these standards
and guidelines.

1.3 Limitations
When working with D-F OUNDATIONS, several limitations apply. As these limitations differ from
model to model, they are provided per model in the Background section.

⋄ The areas of application can be found in:

section 16.2 for bearing piles acc. to the Dutch Eurocode 7 (EC7-NL).
⋄ ⋄ ⋄

section 17.1 for tension piles acc. to the Dutch Eurocode 7 (EC7-NL).
section 18.1 for shallow foundations acc. to the Dutch Eurocode 7 (EC7-NL).
⋄ The problem boundaries can be found in:
section 16.7.1 for bearing piles acc. to the Dutch Eurocode 7 (EC7-NL).
⋄ ⋄ ⋄

section 17.8.1 for tension piles acc. to the Dutch Eurocode 7 (EC7-NL).
section 18.6.1 for shallow foundations acc. to the Dutch Eurocode 7 (EC7-NL).

1.4 Minimum System Requirements

The following minimum system requirements are needed in order to run and install the D-F OUNDATIONS
software:

⋄ Operating systems:
Windows 10
⋄ ⋄

Windows 11 (version 22H2)

⋄ Hardware specifications:
1 GHz Intel Pentium processor or equivalent
⋄ ⋄ ⋄ ⋄

512 MB of RAM available

400 MB free hard disk space
SVGA video card, 1024 × 768 pixels, High colors (16 bits)

1.5 History
With the introduction of the new Dutch standards in 1991, standards for foundation design
were described for the first time (NEN 6740:1991 (NEN, 1991a), NEN 6743:1991 (NEN,
1991b) and NEN 6744:1991 (NEN, 1991c)). This triggered the wish to automate the calcula-
tion models within these standards in a computer program. Deltares, at that time known as
GeoDelft, in cooperation with Fugro, Mos and Gemeentewerken Rotterdam took up this chal-
lenge to create the DOS-program NENGEO, module NENPAAL. This program in its first ver-

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sion offered the possibility to verify bearing piles according to NEN 6740:1991 (NEN, 1991a)
and NEN 6743:1991 (NEN, 1991b) and was completed in 1992.

In version 2.0 design options for the module NENPAAL where added, making it a design as
well as a verification tool.

In version 2.1 Deltares (at that time known as GeoDelft) added the module NENSTAAL.
This module offered the possibility to verify shallow foundations according to NEN 6740:1991
(NEN, 1991a) and NEN 6744:1991 (NEN, 1991c).

Version 3.0 allowed parameters to be overruled in the NENPAAL module, providing more
flexibility to the user of the program.

MFoundation version 4.0 was introduced in 1999. This was the first Windows version of
the program, renamed as MFoundation. This new name emphasized the new objectives of
the program. MFoundation is positioned as a general design tool for foundations (which also
allows verification) instead of primarily being a verification tool.

MFoundation version 4.1 was released in 2000. This version included a new module for
designing tension piles according to the so-called GeoDelft method. This method was derived
from the DOS-software package MTENSION and incorporated in MFoundation as the Tension
Piles (GeoDelft) model.

MFoundation version 4.3 was released in March 2002. This version included a new module
for designing tension piles according to the CUR Report 2001-4, ‘Design of tension piles’
(CUR, 2001). This method represents the latest insights into the design of tension piles and
is incorporated in MFoundation as the tension piles model.

MFoundation version 4.7 was released in December 2002. This version included a major
redesign of the user interface, a number of small bug fixes and a new software security model.

MFoundation version 5.1 was released in January 2006. A tree view has been introduced
in MFoundation’s main window, giving the user an overview of the input data and results, and
fast access to data which can subsequently be easily edited. The former calculation method
‘Belgian method De Beer’ is removed in this version. It will be replaced by a new model (‘Van
Impe / De Beer’) that will be fully compliant with the new Belgian Standard. The Tension Piles
– GeoDelft model is now replaced by the Tension Piles (CUR) model.

MFoundation version 6.1 was released in March 2007. The Bearing Piles (NEN) model is
designed according to NEN 6743-1:2006 (NEN, 2006) and the Shallow Foundations model
according to NEN 6744:2007 (NEN, 2007). The calculation model ‘Belgian method De Beer’
is available. The pile selection has been improved to avoid impossible combinations between
shape and type.

MFoundation version 6.3 was released in October 2008. The calculation model ‘Belgian
method’ has been adapted according to the latest specification of the Belgian Eurocode 7
(WTCB, 2008).

MFoundation version 6.4 was released in April 2010. A new module E-Consult has been
added enabling to check the feasibility of the pile design. A prediction on the drivability of the
chosen piles as well as a review of the experiences in similar designs can be performed using
the experiences from the GeoBrain database. Also new in this version is the option to import
CPTs directly from DINO database. The maximum number of measurements in a CPT-file
has been increased from 5000 to 25000.

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MFoundation version 7.1 was released in June 2010. Eurocode is actively implemented in
Europe on April 2010. In the Netherlands, Eurocode 7 (for geotechnical practice and design)
has been implemented in NEN 9997-1:2009 [Lit 13]. The MFoundation version 7.1 has been
furthermore updated to accommodate this. The pile models (bearing and tension) and shallow
foundation can now be calculated and evaluated based on the Netherlands Eurocode 7 (EC7-
NL). There is however no update for the current Belgian pile model for bearing piles (EC7-B).

D-F OUNDATIONS version 8.1 was released end of 2010. The name of the program has changed:
D-F OUNDATIONS replaces MFoundation. Moreover, the Belgian pile model for bearing piles
(EC7-B) has been updated according to the latest specification of the Belgian Eurocode 7
(WTCB, 2010).

D-F OUNDATIONS version 8.2 was released end of 2012. This version incorporates all changes
due to the release of the latest Euro code NEN 9997-1+C1:2012 (April 2012) (NEN, 2012).
The most important change is the one to the pile clas factors for the models Bearing Piles
(EC7-NL) and Tension Piles (EC7-NL). Not only have the pile type categories been changed
and extended (e.g. the addition of micro piles) but also some designations of the type of
load settlement curves. Furthermore, the new tables for the Bearing Piles model are now
also valid for the Tension Piles model, making the old separate tables for the Tension Piles
obsolete. This also involves a change in the reduction of the bearing capacity due to large
grain sizes for sand and clay for the Tension Piles model. It should be noted that the pile
type "Prefabricated screw pile with grout" is still part of this version eventhough it is no longer
mentioned in the new NEN. It is kept so users are able to recalculate their old projects using
this type. It is therefore advised not to use this type in new projects. Next to the changes in
the pile class factors other changes are:

⋄ Bearing Piles model (EC7-NL): the safety factor for pile groups when calculating the
negative skin friction is reduced from 1.4 to 1.2.
⋄ Bearing Piles model (EC7-NL): the Young’s modulus for wood has been changed from
15.000.000 kN/m2 to 3.600.000 kN/m2 .

Besides the changes in the code, also the next problems are addressed in this version:

⋄ Tension Piles model (EC7-NL): the Report Selection option did not work correctly. This
is fixed.
⋄ All Pile Models, Design Results window: The next process led to an error: perform a de-
sign calculation,go to design results -> Tab ’Text’ ->, change upper limit (for instance)
-> click in the text -> RichEdit line insertion error. This is now fixed.
⋄ Bearing Piles model (EC7-NL): in some cases, the determination of the bearing capacity
of open ended steel pipe piles went wrong, taking into account a wrong pile tip area.
This is now fixed.

Finally, some improvements were made to the text in error messages, reports and the user
interface.

D-F OUNDATIONS version 14.1 (July 2014). This new version incorporates the following changes:

⋄ For the Bearing Piles (EC7-NL) model:

The old exception for CFA-piles for αs (use 0.01 instead of 0.006 when the cpt
⋄

is made after pile installation) is no longer part of NEN-EN version 2012 and is
therefore removed from the program. So now, αs = 0.006 will always be used.
When using a pile with an enlarged base with improper dimensions, the program
⋄

will now produce an error instead of calculation with β = −1.

Trying to calculate when the top of the soil profile is below the first CPT-measurement
⋄

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resulted in an unexpected error. This will now give a neat error message.
⋄ For Tension Piles (EC7-NL) model:
Backward compatibility for reading old MFoundation files for pile types (requires

⋄
conversion to new pile type definitions) is improved.
The weight for hollow pile types is corrected. Note that these are now assumed to
⋄
be empty.
Corrected an error with the determination of the weight of a rectangular pile with
⋄

enlarged base.

D-F OUNDATIONS version 15.1 (April 2015). This new version incorporates the following im-
provements:

⋄ Renaming the materials is now possible for user defined materials. Note that standard
materials can not be renamed as these are used by the standard interpretation models.
⋄ The number of digits in the report for the wall thickness of hollow piles is increased.
⋄ The load settlement curves are now referred to by number (as in the NEN-EN itself) and
no longer by the now obsolete names.
⋄ For Bearing Piles (EC7-NL), the actual used ξ (ξ3 or ξ4 ) is now indicated in the In-
termediate Results File (section 7.3.1.1) as well as the Report in case of Verification
Calculations. For Report:
Verification Complete: as single line in Report just below the ξ -values;
⋄ ⋄

Verification Design: in the tables per calculated depth.

⋄ For Bearing Piles (EC7-NL), the determination of the neutral earth pressure coefficient
K0 for the calculation of the negative skin friction is improved if OCR is not 1 (the Jacky
formula is used), see section 16.5.
⋄ For Shallow Foundations, it is now possible to override the partial factors (see Fig-
ure 6.13).

Besides, the following known bugs are solved:

⋄ It is not possible any more to add boundaries/layers to the profiles graphically beyond
the allowed maximum number of layers.
⋄ The layer thickness for the interpretation model is now remembered for each separate
profile.
⋄ For Bearing Piles (EC7-NL) and Tension Piles (EC7-NL): Tables 10A and 10B for the
determination of ξ3 and ξ4 delivered the wrong (but save) values when the number of
CPT’s equals 10. It now returns the proper values.
⋄ For Bearing Piles (EC7-NL), in the Report, the value given for αs sand/gravel was not
correct in some cases (for mainly manual CPT with only a few CPT values). It is now.
⋄ For Bearing Piles (EC7-NL), the value of αs clay/loam/peat given in the report is not
correct in some cases (for mainly manual CPT with only a few CPT values). It is now.
⋄ For Bearing Piles (EC7-NL), two missing steel pile types (grouted steel piles) are added.
⋄ For Bearing Piles (EC7-NL), the check defined by NEN 9997-1+C2:2017 art A.3.3.3 is
now performed in the main Report, not only the Intermediate Report.
⋄ For Shallow Foundations(EC7-NL), the Zoom limits does now work properly for rectan-
gular foundations.
⋄ For Bearing Piles (EC7-NL), the check on the foundation plan for the pile group criteria
could fail if the centre-to-centre distance of the piles is equal to 10 times the minimum
pile diameter (i.e. the pile group criteria). This is solved.

D-F OUNDATIONS version 16.1 (2016). With this version, license(s) can be borrowed for a
certain period allowing working without connection to the licence server (see Figure 3.7 for
more information). This version also contains small improvements and solved issues (for a
complete list, download the Release Notes from the Download Portal of Deltares).

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D-F OUNDATIONS version 17.1 (2017). In this version, the three Dutch models have been
adapted to the latest version of Eurocode NEN 9997-1 (NL) June 2016 (NEN, 2016). Importing
CPT from the DINO database is not possible anymore because the DINO webservice is not
supported by the Dino portal anymore.
This version also contains small improvements:

⋄ For Bearing Piles (EC7-NL) model:

The safety factor γf;nk can be overruled (see Figure 4.23);
⋄ ⋄

The Report and the Intermediate Results have been extended with more informa-
tion, so as Rc;cal;gem , Rc;cal;min and ξ factor;
When using a user defined pile type, it is now possible to specify it as prefabricated
⋄

or not. This in order to be able to use the proper delta factor (see see Figure 4.14);
The“Almere regels" have been adapted to the new update by the City of Almere
⋄

(01-01-2017);
When using a user defined pile type, it is now possible to specify the required
⋄

reduction of qc;III as percentage (see Figure 4.14);

⋄ For Tension Piles (EC7-NL) model, the factors f1 and f1;average are added in the Design
Results.
⋄ For Shallow Foundations (EC7-NL):
The partial factors can be overruled (see Figure 6.13);
⋄ ⋄

In the Intermediate Results, the value of ze (“ze einde iteratie") based on φ (fgem;d)
has been added.

This version also contains solved issues (for a complete list, download the Release Notes
from the Download Portal of Deltares).

D-F OUNDATIONS version 19.1 (2019). In this version the model Tension Piles (EC-7 NL) has
been extended to include a Verification option. With this option the user can verify design
made with the Tension Piles (EC-7 NL) model according to NEN 9997-1. In addition the
program has been fully updated to the 2017 version of NEN 9997-1 (for example, the use of
the term characteristic instead of representative).

In this version the following bugs are solved:

⋄ For Model Tension Piles (EC-7 NL) model, error in displaying the correct levels for the
option Pile tip levels and net bearing capacity was fixed.
⋄ Model Shallow Foundations (EC-7 NL) model:
The determination of the minimum value for the effective width (b’) was fixed when
⋄

the tip over stability is checked. In this version the real minimum value is deter-
mined.
When the foundation layer is cohesive then the values ae and ze are determined
⋄

based on the fact that φ = 0. If the foundation layer is non-cohesive then the
actual value of φ for the determination of ae and ze .

Also in this version the following improvements were made:

⋄ For all models:

When editing CPT values the user has the option to edit the column Friction [MPa].
⋄ ⋄

Improved the check on the validity of the input file when it is read. Corrupt files are
handled better and result in a error message when read.
Corrected the terms used for limit states (EQU, STR/GEO, SLS) in the program,
⋄

report and manual.

⋄ For Model Tension Piles (EC-7 NL) model:
An explanation of the values Rt;d min and Rt;d gem is added to the results.
⋄

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The value % Clay is replaced by % cohesive layers.

⋄ ⋄
When a CPT is extended manually to reach a certain depth, the program will
discretize it automatically. This leads to more accurate results.
Layout of the design results redefined so that CPT with long names do not effect
⋄ the layout of the result tables.
⋄ For Model Bearing Piles (EC-7 NL) model:
Long chapter headers corrected so that they are visible in the report.
⋄ ⋄

Extra soil type, Sandy Loam, is added, so that it is able to handle the determination
of αs for "Sterk zandig leem" based on the friction ratio when possible.
⋄ For Model Shallow Foundations (EC-7 NL) model:
In case a slope is used, a warning will be shown in case the given foundation level
⋄

is below the toe of the slope. Apart from a warning in the program itself, a warning
is added in the report as well.

D-F OUNDATIONS version 21.1 (2021). For licenses the module system is no longer used,
therefore all functionality in D-F OUNDATIONS is available for all users with a D-F OUNDATIONS
license. Moreover, the GeoBrain Drivability options under the Feasibility menu are not avail-
able anymore. However, the drivability predictions and experiences are still available on the
website www.geobrain.nl.

In the program itself a few new features are added:

⋄ For all models:

The user defined CPT interpretation rule is now stored in the input file itself.
⋄ ⋄

A new option is added for the report which enables the user to specify whether the
CPTs/Profiles are to be numbered in the tables or not.
⋄ For Model Tension Piles (EC-7 NL) model it is now possible to specify a filling for closed
ended steel pipe piles. This filling will be added to the pile weight.
⋄ For Model Bearing Piles (EC-7 NL) model at the excavation window, an option is added
to view the reduced qc-values. Just right click in the CPT view part of the screen and
select the pop menu option "View CPT Values...".

Next to that, a number of bugs are fixed:

⋄ For all models fixed a bug with the interpretation of GEF CPT files that could occur when
switching between CPTs and changing the interpretation model simultaneously.
⋄ For Model Tension Piles (EC-7 NL) model, option Verification: prevented checking the
trajectory when this option is chosen as it plays no part in this.
⋄ For Model Shallow Foundations (EC-7 NL) model, the option Maximize Vertical Loads
no longer produces an error when there are more than 20 elements. So this option can
now be used for up to 200 elements (same as the other options).

Finally a number of improvements are realized:

⋄ For Model Bearing Piles (EC-7 NL) model:

Improved the handling of qc-reduction to 12/15 MPa.
⋄ ⋄

When peat, clay or loam layers are defined to be part of the positive skin friction
zone(s), a warning is provided about this in the program itself as well as in the
report.
⋄ For Model Tension Piles (EC-7 NL) model improved the manual for the formula’s con-
cerning handling of the excavation in Step 2.
⋄ For all models, made sure the location map (when added) is shown in the pictures of
the report too.

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D-F OUNDATIONS version 22.1 (2022). The Belgian standard will change significantly in 2022,
according to report no. 20 of the WTCB. The effort required to fully implement these changes
is that large, that it was decided to no longer support the Belgian standard and therefore to
remove it completely from D-F OUNDATIONS.

A number of bugs are fixed and some improvements are made. The most important changes
are:

⋄ Shallow Foundations: The implementation of Squeeze was still based on the original
NEN (NEN 6744), which required that the foundation layer itself is a non cohesive layer,
followed by a cohesive layer just beneath that layer and within 20 cm of the actual foun-
dation level. This is now corrected for the description in (NEN, 2017). The demand of a
non cohesive squeeze layer has been dropped. This means that for the determination
of hsq (height or rather thickness of the squeezed layer) a cohesive foundation layer
must be taken into account. So in that case hsq starts at foundation level rather that
at the top of the cohesive layer below foundation level. Some of the benchmarks are
modified for changes in the squeeze model.
⋄ Shallow Foundations: test for punching through (‘toets op doorponsen’) is implemented
better. An extra check is added on the foundation level if the ‘punching’ level is still
above the toe of the berm. If not, the situation must be handled as if the whole founda-
tion is placed on a horizontal surface with as level the level of the toe of the berm.
⋄ Shallow Foundations: The determination of ae (influence width) for the drained situation
is corrected. It did depend on the φ of the foundation layer where it should depend on
the iterated φ value.
⋄ Shallow Foundations: The determination of the calculation case (A, B or C) for an
undrained situation was not always correct.
⋄ Shallow Foundations: Small corrections in calculation of angle α for λc .
⋄ Tension Piles: When calculations are made with different pile types and grouping per
pile type per pile group is not possible, a correct error message is now generated.
⋄ Tension Piles, Verification: When using very low pile loads the calculation failed.
⋄ Tension Piles: Implemented import and export of pile types, like it was already possible
for model Bearing Piles.
⋄ An extra option Use compression was added to the Export Options window. Turning
this option off can solve the problem with an ’Integer Overflow’ error when generating a
report. By default this option is off.
⋄ Installation and de-installation of multiple versions of D-F OUNDATIONS is now possible.

D-F OUNDATIONS version 23.1 (2023). A number of bugs are fixed and some improvements
are made. The most important changes are:

⋄ For Bearing Piles model, the limit values for qc;z;a -reduction and qb;max given in the NEN
can be overridden in the Calculation dialog (section 4.6.1).
⋄ For Bearing Piles and Tension Piles mode, when using the Generate pile grid button in
the Pile Properties dialog, an option is added to set the coordinates given in the dialog
relative to a soil profile (Figure 4.16).
⋄ For Shallow Foundations model, due to a new interpretation of the NEN 9997-1+C2:2017
standard, the way that Squeeze as a failure mechanism is to be interpreted is changed.
In the old practice, the squeeze calculation was optional for “case B” in case of a
undrained situation. Then a “normal” calculation was performed and if applicable the
squeeze calculation too. The best result could be used to check against the load(s). In
the new practice, squeeze is always to be checked (for “case A” this can never happen;
so in practice for “case B” and “case C”) and calculated when applicable (see condition
at 6.5.2.2 (s) of NEN 9997-1+C2:2017). And now the worst result is to be used to check
against the load(s).

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1.6 Definitions and Symbols

The definitions and symbols used in D-F OUNDATIONS are explained in the Background section.
In section 16.6, section 17.7 and section 18.5, the definitions and symbols for each model are
provided.

1.7 Getting Help

From the Help menu, choose the Manual option to open the User Manual of D-F OUNDATIONS
in PDF format. Here help on a specific topic can be found by entering a specific word in the
Find field of the PDF reader.

Clicking on the Help button situated at the bottom-right side of a window will open the User
Manual.

1.8 Getting Support

Deltares Systems tools are supported by Deltares. A group of 70 people in software develop-
ment ensures continuous research and development. Support is provided by the developers
and if necessary by the appropriate Deltares experts. These experts can provide consultancy
backup as well.

If problems are encountered, the first step should be to consult the online Support of D-F OUNDATIONS
on the Deltares website. Different information about the program can be found under Support
(Figure 1.1):

⋄ In ‘Known issues’ the issues of the program are listed.

⋄ In ‘Frequently asked questions’, the most frequently asked technical questions and their
answers are listed.

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Figure 1.1: Deltares website for this software

At the Download Portal of Deltares, the Release Notes listing the differences between an old
and a new version can be downloaded.

If the solution cannot be found there, then the problem description can be e-mailed to the
Deltares Systems support team. When sending a problem description, please add a full
description of the working environment. To do this conveniently:

⋄ Open the program.

⋄ If possible, open a project that can illustrate the question.
⋄ Choose the Support option in the Help menu. The System Info tab contains all relevant
information about the system and the Deltares software. The Problem Description tab
enables a description of the problem encountered to be added.

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Figure 1.2: Support window, Problem Description tab

⋄ After clicking on the Send button, the program will open the user’s default mail application.
The sender and subject are filed out along with the Description of the problem and the
System info as the body of the email.

The problem report can also be saved to a file and the document can be emailed to:
software.support@deltares.nl.

1.9 Deltares
Since January 1st 2008, GeoDelft together with parts of Rijkswaterstaat /DWW, RIKZ and
RIZA, WL |Delft Hydraulics and a part of TNO Built Environment and Geosciences are form-
ing the Deltares Institute, a new and independent institute for applied research and specialist
advice. Founded in 1934, GeoDelft was one of the oldest and most renowned geotechnical
engineering institutes of the world. As a Dutch national Grand Technological Institute (GTI),
Deltares role is to obtain, generate and disseminate geotechnical know-how. The institute is
an international leader in research and consultancy into the behavior of soft soils (sand clay
and peat) and management of the geo-ecological consequences which arise from these ac-
tivities. Again and again subsoil related uncertainties and risks appear to be the key factors
in civil engineering risk management. Having the processes to manage these uncertainties
makes Deltares the obvious Partner in risk management for all parties involved in the civil and
environmental construction sector. Deltares teams are continually working on new mecha-
nisms, applications and concepts to facilitate the risk management process, the most recent
of which is the launch of the concept "GeoQ" into the geotechnical sector. For more informa-
tion on Deltares, visit the Deltares website: www.deltares.com.

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1.10 Deltares Systems

On a more practical level Deltares is active in disseminating and implementing geotechnical
knowledge and experience into the civil engineering and construction sectors. It is recognized
that ICT-based developments will be the basis of knowledge transfer in the next decades.
Deltares Systems hosts internet-facilitated tools, of which D-F OUNDATIONS is part, and expe-
rience databases and generally applicable geotechnical software for the calculation of slope
stability, settlement, groundwater flow and other phenomena.
For more information about geotechnical softwares, including download options, visit
https://www.deltares.nl/en/software-solutions/.

1.11 On-line software

Besides purchased software, Deltares Systems tools are available as an on-line service. The
input can be created over the internet. Heavy duty calculation servers at Deltares guarantee
quick analysis, while results are presented on-line. Users can view and print results as well
as locally store project files. Once connected, clients are charged by the hour.
For more information, please contact the Deltares Sales team: software@deltares.nl.

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 2 Getting Started
This chapter section aims to familiarize the user with the structure and user interface of
D-F OUNDATIONS. The Tutorial section (chapter 8 to chapter 14) uses a selection of case studies
to introduce the program’s functions.

2.1 Starting D-F OUNDATIONS

To start D-F OUNDATIONS, click Start and then find D-Foundations under Programs on the Win-
dows menu bar, or double-click a D-F OUNDATIONS input file that was generated during a previ-
ous session.

When D-F OUNDATIONS is started from the Windows menu bar, the last project that was worked
on will open automatically (unless the program has been configured otherwise in the Program
Options window, reached from the Tools menu) and D-F OUNDATIONS will display the main
window (section 2.2).

2.2 Main Window

When D-F OUNDATIONS is started, the main window is displayed (Figure 2.1). This window
contains a menu bar (section 2.2.1), an icon bar (section 2.2.2), a tree view (section 2.2.3)
providing easy access to all input windows, allowing project data to be edited and added
quickly and efficiently, a title panel (section 2.2.4) and a status bar (section 2.2.5).

The caption of the main window of D-F OUNDATIONS displays the program name, followed by
the model. When a new file is created, the default model is Bearing Piles (EC7-NL) and the
project name is Project1.

Figure 2.1: D-F OUNDATIONS main window

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2.2.1 Menu bar

To access a menu, click a menu name on the menu bar and select the appropriate option.

Figure 2.2: D-F OUNDATIONS menu bar

The menu bar contains the following functions:

File Standard Windows options for opening and saving files as well as several
options for exporting and printing the contents of various windows (sec-
tion 3.1).
Project Options for defining the project and for viewing the input file (section 3.4).
Calculation Option to open the Calculation window where the calculation can be defined
and started.
Results Option to open the Report Selection window where the report content can
be chosen (section 7.4).
Tools Options for editing the program defaults including defining the model used
to interpret CPTs (section 3.2).
Window Default Windows options for arranging the program windows and choosing
the active window.
Help Online Help options (section 3.3).

2.2.2 Icon bar

The buttons on the icon bar can be used to quickly access frequently used functions.

Figure 2.3: D-F OUNDATIONS icon bar

Click on the following buttons to activate the corresponding functions:

Start a new D-F OUNDATIONS project with or without using the wizard.
Open the input file of an existing project.
Save the input file of the current project.
Print the contents of the active window.
Display a print preview.
Open the Project Properties window. Here various preferences can be set for
viewing data.
Open the Calculation window.
Display the contents of online Help.

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Display the first page of the Deltares software website:

https://www.deltares.nl/en/software-solutions/

2.2.3 Tree view

The tree view on the left side of D-F OUNDATIONS main window can be used to navigate through
all input, calculation and result windows of the program. When no project is open, the tree
view has no function (Figure 2.4).

Figure 2.4: D-F OUNDATIONS tree view when no project is opened

After a project has been opened by choosing New, New Wizard or Open from the File menu,
the tree view shows an overview of all available input windows (Figure 2.5).

Figure 2.5: Tree view when a (Bearing Piles EC7-NL) project is opened

The available input windows of the tree view depend on the selected model:

⋄ Refer to section 4.1 for Bearing Piles EC7-NL;

⋄ Refer to section 5.1 for Tension Piles EC7-NL;
⋄ Refer to section 6.1 for Shallow Foundations EC7-NL.

Navigate through the input windows by just selecting nodes in the tree. For example, if the

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Materials node is selected a window opens that enables all material data to be viewed and
edited.

Some nodes are only present in the tree to reveal the structure of the input data. For example,
the Soil node itself does not correspond to an input window. It has three sub-nodes: Mate-
rials, Profiles and Slopes (for the shallow foundations model only), that correspond to three
windows that contain all soil data.

For some types of input data, the tree view can be used to add or delete new items. For
example, if the Types node is selected then a list of all available foundation types for the
current project is given. To extend a list, right click the node containing the list (e.g. Types)
and click New in the pop-up menu that appears (Figure 2.6). To delete an item from a list,
right click the item in the list and click Delete in the pop-up menu that appears.

Figure 2.6: The tree view may be manipulated using pop-up menus

2.2.4 Title panel

This panel situated below the tree view displays the project titles, as entered in the Project
Properties – Description window (section 3.5). This panel is displayed only if the correspond-
ing checkbox in the View tab of the Program Options window (section 3.2.1) is selected.

Figure 2.7: Title panel and Status bar at the bottom of the main window

2.2.5 Status bar

This bar situated at the bottom of the main window displays a description of the selected icon
of the icon bar (section 2.2.2) or button of the current window. This bar is displayed only if
the corresponding checkbox in the View tab of the Program Options window (section 3.2.1) is
selected.

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2.3 Files
*.foi D-F OUNDATIONS input file (ASCII):
File containing all relevant input data needed for a calculation in
D-F OUNDATIONS.
*.fos Settings file (ASCII):
Working file with settings data. This file does not contain any information that
is relevant for the calculation, but only settings that apply to the representation
of the data, such as the grid size.
*.for Intermediate results file (ASCII):
Working file containing the intermediate results of a D-F OUNDATIONS calcula-
tion. This file is used on generating the Intermediate Results (section 7.3). Not
available for the Tension Piles (EC7-NL) model.
*.fod Dump file (ASCII):
Working file containing the results of a D-F OUNDATIONS calculation. This file is
used on generating a report or a graphical representation of the results.
*.cpt Cone Penetration Test file (ASCII):
Contains CPT records in the format used by previous versions of
D-F OUNDATIONS.
*.gef Geotechnical Exchange Format file (ASCII):
GEF file Contains CPT records in the format as developed by CUR (Geotech-
nical exchange format for CPT-data, 1999-2004).
*.son Cone Penetration Test file (ASCII):
Contains CPT records as used by NENGEO, the predecessor of
D-F OUNDATIONS.
*.jpg Joint Photographic Group file:
Picture to be used as background map (section 3.4.3).
*.jpeg Joint Photographic Experts Group file:
Picture to be used as background map (section 3.4.3).
*bmp Windows Bitmap file:
Picture to be used as background map (section 3.4.3).
*.emf Enhanced Metafile:
Picture to be used as background map (section 3.4.3).
*.wmf Windows Metafile:
Picture to be used as background map (section 3.4.3).
*.fmd Matrix Data (ASCII):
Contains pile grid data. Only available when the Generate pile grid option is
used.
*.wmf Windows Meta File WMF file(binary):
Export file for images, for instance containing the image of the current Top
View Foundation window within an added picture frame. Files of this type can
be used to import the image into applications such as Microsoft Word.
*.fop Pile Type Library file (ASCII):
Import/Export file, containing the definition of pile types.FOP-files may be used
to create a pile type database, which enables users to reuse pile type informa-
tion in different projects.
*.pdf Adobe PDF-files:
Export file for reports.

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*.rtf Rich text format\-files

Export file for reports.
*.txt ASCII-text-files
Export file for reports.

2.4 Tips and Tricks

2.4.1 Keyboard shortcuts

Keyboard shortcuts given in Table 2.1 are another way to reach the features of D-F OUNDATIONS
directly without selecting it from the bar menu. These shortcuts are also indicated in the
corresponding sub-menus.

Table 2.1: Keyboard shortcuts for D-F OUNDATIONS

Keyboard shortcut Opened window

Ctrl + N New
Ctrl + W New Wizard
Ctrl + O Open
Ctrl + S Save
F12 Save As
Ctrl + P Print Report
Ctrl + M Model
F9 Start Calculation

2.4.2 Exporting figures and reports

All figures in D-F OUNDATIONS such as top view and graphical output can be exported in WMF
(Windows Meta Files) format. In the File menu, select the option Export Active Window to
save the figures in a file. This file can be later imported in a Word document for example or
added as annex in a report. The option Copy Active Window to Clipboard from the File menu
can also be used to copy directly the figure in a Word document.

The report can be entirely exported as PDF (Portable Document Format) or RTF (Rich Text
Format) file. To look at a PDF file Adobe Reader can be used. A RTF file can be opened
and edited with word processors like MS Word. Before exporting the report, a selection of the
relevant parts can be done with the option Report Selection (section 7.4.3).

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2.4.3 Copying part of a table

It is possible to select and then copy part of a table in another document (an Excel sheet
for example). If the cursor is placed on the left-hand side of a cell of the table, the cursor
changes in an arrow which points from bottom left to top right. Select a specific area by using
the mouse (see a) in Figure 2.8). Then, using the copy button (or ctrl+C) this area can be
copied.

a) b)

c) d)
Figure 2.8: Selection of different parts of a table using the arrow cursor

To select a row, click on the cell before the row number (see b) in Figure 2.8). To select a
column, click on the top cell of the column (see c) in Figure 2.8). To select the complete table,
click on the top left cell (see d) in Figure 2.8).

In some tables the buttons Cut, Copy, and Paste are also present at the left hand.

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 3 General
This chapter contains a detailed description of the available menu options for inputting data
for a project, and for calculating and viewing the results.

The examples in the Tutorial section (chapter 8 to chapter 14) provide a convenient starting
point for familiarization with the program.

3.1 File menu

Besides the familiar Windows options for opening and saving files, the File menu contains a
number of options specific to D-F OUNDATIONS:

⋄ New Wizard
Use this option to create a new project quickly. D-F OUNDATIONS takes the user through
the required input windows: first the Model window (section 3.4.1) to select the model
and then the Import CPTs from file window to create a soil profile. D-F OUNDATIONS will
automatically generate four square piles with width 220, 250, 290 and 320 mm and with
a pile type depending on the model:
– For Bearing Piles (EC7-NL) model, prefabricated concrete pile;
– For Tension Piles (EC7-NL) model, driven straight-sided precast concrete pile.
D-F OUNDATIONS will also add a single pile in the pile plan, with the horizontal co-ordinates
of the CPT shifted with 5 m and a Pile head level equal to the ground level.
⋄ Export Active Window
Use this option to export the contents of the active window as a Windows Meta File
(*.wmf) for pictures and as text file (*.txt) for the input file.
⋄ Export Report
This option allows the report to be exported in a specified format. The following options
are available:
pdf Adobe PDF;
⋄ ⋄ ⋄ ⋄

rtf Rich text;

txt HTML (web-page);
csv Comma separated.

Figure 3.1: Export Report window

Save as Select the export format.

type
Options... Clicking this button opens the export options dialog.

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The export options dialog is only applicable to the PDF format.

Figure 3.2: Export Options window

Picture The quality of the picture. The higher the quality, the larger the size of the
quality resulting PDF-document will be.
Use com- Using compression reduces the size of the resulting PDF-document.
pression

⋄ Page Setup
Use this option to define the way plots and reports should be printed. Here the printer,
paper size, orientation and margins can be defined. For plots, it can also be specified
whether and where axes are required. Click Autofit to let the program define the best fit
for data on the page.
⋄ Print Preview Active Window
Use this option to display a preview of the printout of the current contents of some of
the input windows (such as Top View Foundation and Excavation window).
⋄ Print Active Window
Print the current contents of some of the input windows (such as Top View Foundation
and Excavation window).
⋄ Print Preview Report
Use this option to display a preview of the printout of the current contents of Report
window.
⋄ Print Report
Print the current contents of the Report window.

3.2 Tools menu

3.2.1 Program Options

On the menu bar, click Tools and then choose Program Options to open the corresponding
input window. The various tabs in this window allow the default settings for D-F OUNDATIONS to
be specified.

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Program Options – View

Figure 3.3: Program Options window, View tab

Select or deselect the check boxes to indicate whether the toolbar, status bar or title panel
should be displayed each time D-F OUNDATIONS is started.

Program Options – General

Figure 3.4: Program Options window, General tab

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Start-up with Click one of these toggle buttons to determine whether a project should be
opened or initiated when the program is started.
No project: Each time D-F OUNDATIONS is started, the buttons in the toolbar
or the options in the File menu must be used to open an existing project or
to start a new one.
Last used project: Each time D-F OUNDATIONS is started, the last project that
was worked on is opened automatically.
New project: Each time D-F OUNDATIONS is started, a new project is created
ready for fresh input information.
Note that this option is ignored when the program is started by double-
clicking an input file.
Save on The toggle buttons determine how input data is saved prior to calculation.
Calculation The input data can either be saved automatically, using the same file name
each time, or a file name can be specified each time the data is saved.
Always Save: Previously saved project data will be overwritten.
Always Save As: The ’Save As’ window will be displayed. This allows sav-
ing the project data with a file name. In this way, previously saved project
data will NOT be overwritten.
Use Enter The toggle buttons allow the way the Enter key is used in the program:
key to either as an equivalent of pressing the default button (Windows-style) or to
shift the focus to the next item in a window (for users accustomed to the
DOS version(s) of the program).

Program Options – Locations

Figure 3.5: Program Options window, Locations tab

Working Either mark the checkbox to automatically make the last used directory the
directory working directory, or unmark the checkbox and specify a default path for
the working directory, which will be set automatically when D-F OUNDATIONS
is started.

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Program Options – Language

Figure 3.6: Program Options window, Language tab

Select the language to be used in the D-F OUNDATIONS windows and on printouts.

Interface The only interface language supported is English. This drop-down box is
language provided for compliance with other Deltares Systems programs. The num-
ber of interface languages may be extended in the future.
Output Two output languages are supported, English and Dutch. The output lan-
language guage is used in all results (text or graphs) that are printed on paper. Note
that the output settings do not apply to the intermediate results file, which is
available in Dutch only. The number of output languages may be extended
in the future.

Program Options – License

For a D-F OUNDATIONS installation based on floating licenses, the License tab can be used to
claim a license for a particular time with the Borrowing option.

For a D-F OUNDATIONS installation based on a license dongle, the Borrowing option is not avail-
able.

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Figure 3.7: Program Options window, License tab

Click this button to see how many licenses are (at this moment) in use and
who (within the company) is using them.

Click this button to borrow the license for a certain period. The license will
be taken from the server pool and will be available on this computer even if
no connection to the license server is available. Set the date and time for
the expiration of the borrowing and press OK.

Click this button to end the borrow immediately.

Program Options – CPT Interpretation

Figure 3.8: Program Options window, CPT Interpretation tab

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Automatic copy Mark this checkbox to interpret the CPT automatically after import. If the
of interpretation checkbox is unmarked press the Transform the interpreted CPT into a
to profile profile button in the Profile window to interpret the CPT manually.

3.2.2 CPT interpretation model

On the menu bar, click the CPT Interpretation Model in the Tools menu, to open the CPT In-
terpretation Model window. This window displays the definition of standard CPT interpretation
models and also enables the definition of a user-defined interpretation model using a set of
so-called rules. Each rule describes a certain soil type by defining the relationship between
the CPT resistance and the Friction Ratio. These relationships are also displayed in a graph.
The friction ratio is defined as the shear resistance as a percentage of the cone resistance.

In the Interpretation Settings sub-window, a default model to be used to interpret newly im-
ported CPTs can be selected. The minimum layer thickness can also be modified for the
default CPT interpretation model. This minimum layer thickness setting is especially useful for
avoiding insignificantly small layers.

The supported standard models are:

⋄ 3-type rule. A basic model, differentiating between sand, clay and peat.
⋄ CUR rule. 6 different soil types, an extension of the classification according Robertson
and Campanella (1983), also printed in figure A.2 of CUR (1992).
⋄ NEN rule. 14 different soil types, according to the Dutch standard NEN 9997-1+C2:2017.
⋄ Qc only rule. A special rule, using only the cone resistance (not the frictional resis-
tance), developed especially for the Belgian mechanical CPT type M4 which doesn’t
provide the frictional resistance.

A user-defined model can also be added as described below:

⋄ To start a user-defined model from a standard template, click Copy to User Defined to copy
the 3-type rule, CUR rule, NEN rule or Qc only rule contents to the User Defined model.
⋄ Use the Add, Insert, Delete and Rename buttons to add or delete rules.
⋄ Select a rule in the Rule name sub-window, and select the corresponding soil type from
those available in the material library.
⋄ Define or change the Soil name and the rule that describes the soil type in the table con-
tained in the Upper classification limit sub-window. Rules should be defined starting in the
top left of the diagram and working towards the bottom right. Rules should not intersect
within the limits of the diagram.
⋄ Click Update Chart to redraw the lines on the chart according to the changes made.

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Figure 3.9: CPT Interpretation Model window

In the Interpretation settings sub-window the Selected default model and the Default minimum
layer thickness options can be used to select the default interpretation model and minimum
layer thickness used for interpreting all CPTs. These values can be changed for individual
CPTs in the Soil – Profiles window (section 4.3.2.3, section 5.3.2.3 and section 6.2.2.3).

3.3 Help menu

The Help menu allows access to different options.

3.3.1 Manual
Select the Manual option from the Help menu to open the User Manual of D-F OUNDATIONS in
PDF format. Here help on a specific topic can be found by entering a specific word in the Find
field of the PDF reader.

3.3.2 Verification Report

Select the Verification Report option from the Help menu to open the Verification Report
of D-F OUNDATIONS in PDF format. In this report, the different benchmarks used to test the
correctness of the output are described. For more information refer to chapter 19.

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3.3.3 Log Messages

If errors are found in the input, no calculation can be performed and D-F OUNDATIONS opens
the Log Messages window displaying more details about the error(s). Those errors must be
corrected before performing a new calculation. To view those errors at any time, select the
Log Messages option from the Help menu. They are also written in the *.log file. They will
be overwritten the next time a calculation is started. The log messages can also contain
warnings, but they are not blocking for a calculation.

Figure 3.10: Log Messages window

3.3.4 Deltares Software Website

Select Deltares Software Website option from the Help menu to visit the Deltares software
website (https://www.deltares.nl/en/software-solutions/) for the latest news.

3.3.5 Support
Use the Support option from the Help menu to open the Support window in which program
errors can be registered. Refer to 1.8 for a detailed description of this window.

3.3.6 About
Use the About option from the Help menu to display the About D-Foundations window which
provides software information (for example the version of the software).

3.4 Project menu

Before analysis can be performed, the project data needs to be input. Which data should
be entered depends on the selected calculation model (see section 3.4.1). How the data are
represented graphically depends on the options selected in the Project Properties window
(see section 3.4.2).

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3.4.1 Model
Choose Model from the Project menu to display the Model window. Project menu the calcu-
lation model, used to generate the project results, can be selected.

Figure 3.11: Model window

Select the required model from:

⋄ Bearing Piles (EC7-NL)

⋄ Bearing Piles (EC-B)
⋄ Tension Piles (EC7-NL)
⋄ Shallow Foundations (EC7-NL)

Each model requires specific project data. Changing the selected model for an existing project
may mean that some data will need to be edited, or additional information added.

3.4.2 Project Properties

Choose Properties from the Project menu to display the window where the elements to be
displayed in the graphical representation of input and output data can be selected.

The window contains three tabs:

⋄ Top View Foundation

⋄ Load Settlement Curve
⋄ View CPT / Profile

Mark the Save as default checkbox to apply the specified settings every time D-F OUNDATIONS
is used.

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Project Properties – Top View Foundation

Figure 3.12: Project Properties window, Top View Foundation tab

This window contains the following checkboxes relevant to the Top View Foundation window
(to view this window select the title in the tree view on the left):

Pile Enable this checkbox to display the pile numbers/pile titles in the Top View
numbers Foundation window.
CPT titles Enable this checkbox to display the titles of the CPTs.
Rulers Enable this checkbox to show the rulers at the top and side of the window.
Large Enable this checkbox to use the large cross-hair cursor.
cursor
Info bar Enable this checkbox to display the Info bar at the bottom of the window.
The Info bar displays the cursor coordinates, the view mode and the ID of
the selected object.
Legend Use this checkbox to display or hide the legend in the Top View Foundation
window. The legend explains the symbols used in this view.
Show grid Enable this checkbox to display the grid.
Snap to grid Enable this checkbox to make objects align to the grid automatically when
they are moved or positioned.

Project Properties – Load Settlement Curve

Figure 3.13: Project Properties window, Load Settlement Curve tab

This window contains the following checkboxes relevant to the Load Settlement Curve window
(to view this window select the title in the tree view on the left):

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Rulers Enable this checkbox to show the rulers at the top and side of the window.
Large Enable this checkbox to use the large cross-hair cursor.
cursor
Info bar Enable this checkbox to display the Info bar at the bottom of the window.
The Info bar displays the cursor coordinates, the view mode and the ID of
the selected object.

Project Properties – View CPT/Profile

Figure 3.14: Project Properties window, View CPT/Profile tab

Click the appropriate toggle button to determine which names for the soil materials will be
used when viewing CPT profiles.

3.4.3 Location Map

Choose Location Map from the Project menu to display the Location Map window where a
picture can be imported and then visualized in the Top View Foundation window as back-
ground map. This can help the user to check and/or adjust the positions of the inputted CPTs
and piles.

Figure 3.15: Location Map window

Background Select the picture (in format JPG, JPEG, BMP, EMF or WMF) to be used as
Picture background map.
Left Enter the X-coordinate of the map left side.
Right Enter the X-coordinate of the map right side.
Top Enter the Y-coordinate of the map top side.

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Bottom Enter the Y-coordinate of the map bottom side.

When clicking OK in the Location Map window, the Top View Foundation window automati-
cally opens (Figure 3.16) displaying the background map.

Figure 3.16: Top View Foundation window showing the location map as background pic-
ture

3.4.4 View Input File

On the menu bar, click Project and then choose View Input File to display an overview of the
input data.

The data will be displayed in the D-F OUNDATIONS main window. Click Print Active Window in
the File menu to print the displayed file.

3.5 Project Description

Before starting a calculation with D-F OUNDATIONS, data that describe and identify the project
can be entered. These data do not affect the results of the calculation, but may be very useful
when displayed in output reports and plots.

The input window containing the relevant input fields may be opened by selecting the Project
Properties – Description node in the input tree.

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Figure 3.17: Project Properties – Description window

In this window the following information can be entered:

Title 1 Use Title 1 to give the calculation a unique, easily recognizable

Title 2 name. Title 2 can be added to give more specific characteris-
tics of the calculation.
Title 3 Contains the name of the project file after saving the calcula-
tion. The user is prompted to enter a name for the project file
when saving a calculation, if it has not already been saved.
All three titles will be included on printed output.
Date Enter the date to be used on all printouts. This can either be
a fixed date entered in the dialog box (e.g. the start date of
the project) or the current date, enabled by selecting the Use
current date checkbox.
Drawn by Enter the name of the person who has performed the calcula-
tion or initiated the printout.
Project ID Enter the project ID.
Annex ID Specify the annex number of the printout.
Geotechnical consultant / In these fields the names of the principal people or parties
Design engineer involved in the project can be entered.
superstructure / Principal If entered, these names will be included in the report that can
be printed by D-F OUNDATIONS.
Location Enter the location of the project. If entered, this data will be
included in the report.

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3.6 Batch Calculation

Next to running calculations from within the program, D-F OUNDATIONS offers the possibility to
perform calculations in batch which means successive calculations for different input files.
This can be useful for time consuming calculations. To do so, D-F OUNDATIONS must be started
from the Run window by specifying its location followed by /b, optionally by /p and optionally
by the name of an inputfile or a folder, as shown in Figure 3.18.

Figure 3.18: Run window

When the batch calculation option, /b, is used without additional options, the Start Batch Cal-
culation window opens where the location (folder ) of the files must be specified (Figure 3.19).
Optionally, all files in sub folders can be included in the calculations too.

Figure 3.19: Start Batch Processing window

D-F OUNDATIONS will run the specified files successively. When running the batch process, a
progress window (Figure 3.20) will appear to report the status of the process. The calculation
can be aborted during the calculation. The summary of the calculation as shown in the Batch
Processing Progress window is also written to the file Batchlog.txt, which will be written in the
specified folder.

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Figure 3.20: Batch Processing Progress window

At the end of the batch process, this window and D-F OUNDATIONS can be closed with Close.

When the batch calculation option /b is used in combination with a file or folder name, the
specified file or files within the folder are calculated. The progress window is not shown and
the summary calculations can be viewed in the file Batchlog.txt.

When the batch calculation option /b is used in combination with both the option /p as well
as a file or folder name, the specified file(s) are calculated. In this case, the progress window
(Figure 3.20) is shown and the summary calculations can be viewed in the file Batchlog.txt.

Batch calculations without any progress windows are used in the GEOLib module, where
python scripts can be used to automatically create and run a large number of input files.

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 4 Bearing Piles (EC7-NL) – Input & Calculations
Two types of data are required to perform a calculation using D-F OUNDATIONS:

⋄ Firstly, data needs to be input in order to determine the soil behavior. This data in-
cludes CPTs with their corresponding soil profiles, including the ground water level, the
expected ground level settlement and so on. This data is entered in the windows that
appear when selecting the sub-nodes below the Soil node in the tree view.
⋄ Secondly, data is required to specify the construction (of the foundation), e.g. pile type,
pile dimensions, pile plan and so on. The relevant options can be found in the windows
that appear when selecting the sub-nodes below the Foundation node in the tree view.

When the project includes an excavation, data concerning this excavation must be entered
at the Excavation node in the tree view. Before calculating the project design, a number
of options can be specified that will apply to all piles in the window that appears when the
Calculation node is selected in the tree view.

4.1 Tree view

Figure 4.1: Main window for the Bearing Piles (EC7-NL) model

For the Bearing Piles (EC7-NL) model, the tree view contains the following nodes and sub-
nodes:

Project Properties Use this option to describe and identify the project.
/ Description
Project Properties Use this option to specify the execution time of CPTs relative to the
/ Construction pile installation. This information is needed to determine whether
Sequence the problem qualifies for certain exceptions made in NEN 9997-
1+C2:2017.
Soil / Materials Use this option to enter the soil material properties.
Soil / Profiles Use this option to enter and view a soil profile for each CPT, as well
as to enter additional data related to the CPT.

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Foundation / Pile Use this option to enter the required pile types. The pile type can be
Types specified, and its dimensions entered.
Foundations / Pile Use this option to define the pile plan. Apart from the pile positions,
Properties the pile head level, a superimposed load next to the pile (if required)
and the pile load are entered here. This data can be entered for each
pile separately or a grid of piles can be generated at once.
Foundations / Top Use this option to display a graphic representation of entered piles
View Foundation and CPTs.
Excavation Use this option to specify the excavation level along with some addi-
tional parameters related to the effect of an excavation.
Calculation Use this option to specify the calculation settings and verification re-
quirements, and to execute the actual calculation.
Results / Load- Use this option to view the load-settlement curve. This option is avail-
Settlement Curve able only if this curve has actually been calculated (using the verifi-
cation options).
Results / Design Use this option to view the results of trajectory-based calculation
options (Preliminary Design/‘Indication bearing capacity’ and ‘Pile
tip levels and net bearing capacity’ options and Verification Bearing
Piles/ ‘Design’). The results can be viewed in text format and when
possible in graphic format. This option is available only if one of the
above calculations has been performed.
Results / Use this option to view the intermediate results file, if there is one.
Intermediate Calculation results are written to this file if the Write intermediate
results checkbox has been enabled in the Options sub-window of
the Calculation window.
Results / Report Use this option to view the output file, input data, and calculation
results in a report.

4.2 Construction Sequence

Click on the Construction Sequence node under Project Properties in the tree view on the left
of the screen. This will open the Project Properties – Construction Sequence window where
the relative timing of CPTs with respect to the installation of the piles and the excavation can
be specified.

With this option the user can specify if D-F OUNDATIONS has to take the effect of an excava-
tion and/or soil compaction due to pile driving into account. These two effects are reducing
respectively increasing the CPT values and are dependent on the time in the construction
process when the CPT is executed.

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Figure 4.2: Construction Sequence window for the Bearing Piles (EC7-NL) model

As default value the time order CPT – Excavation – Install is used as this is the most common
order in the construction process.

4.3 Soil
In the tree view, the Soil node contains the sub-nodes Materials and Profiles, which should
be selected to enter or view the corresponding input data.

4.3.1 Materials
In the Soil – Materials window the materials and corresponding parameters for the project are
entered.

Figure 4.3: Soil – Materials window for Bearing Piles (EC7-NL) model

Note: The table, at start-up, is filled automatically with a list of materials obtained from Table
2.b of NEN 9997-1+C2:2017.

To make clear which materials are used in the profiles, use the Show Materials filter. To show
only the materials which are used in the profiles, select Used materials only. If All is selected,
all available materials are shown.

There are three ways to fill in the soil parameters:

⋄ section 4.3.1.1 Adding a ‘standard’ material (including its soil parameters) from Table
2.b as defined in NEN 9997-1+C2:2017.
⋄ section 4.3.1.2 Adding manually a material and its required soil parameters.

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⋄ section 4.3.1.3 Changing the properties of an existing material by matching them with
the properties of a ‘NEN material’ (i.e. from Table 2.b of NEN 9997-1+C2:2017).

4.3.1.1 Materials – Add from ‘Standard’

The Add from NEN 9997-1 button can be used to select a ‘standard’ material (including its
soil parameters) from Table 2.b as defined in NEN 9997-1+C2:2017.

1. To add a ‘standard’ material click the Add from 9997-1 button to open the NEN 9997-1
Table 2.b window (Figure 4.4).

Figure 4.4: NEN 9997-1 Table 2.b (Table 2.b of NEN 9997-1+C2:2017) window for Bear-
ing Piles (EC7-NL) model

2. Select the required soil and then click OK to return to the Soil – Materials window where
the information for the selected soil will have been filled in.
3. To select and add more than one soil at the time, use the Shift or Control key when select-
ing.

Note: The NEN 9997-1 Table 2.b window displays either the high or the low values accord-
ing to the influence of the parameters. For example, for the Bearing Piles model the soil
weight has a negative influence so the high values must be chosen whereas for Tension Piles
(EC7-NL) and Shallow Foundations models, the soil weight has a beneficial effect on the bear-
ing/tension capacity so the low values much be chosen. The program will for each calculation
only use the materials as selected in the Materials window. It will never take values from the
standard tables directly. So the user must make sure the proper values have been selected.
For instance, when first performing a Bearing Piles (EC7-NL) calculation (with ’high’ values),
the user should adapt the values before performing a Tension Piles (EC7-NL) calculation by
clicking the button in the Soil – Materials window.

Note: Only the parameter D50 (Median) (required for the soil types Gravel and Sand) must
always be provided by the user. D-F OUNDATIONS provides a default D50 , but if the soil is coarse
grained then the correct value will need to be input for correct calculation.

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4.3.1.2 Materials – Add manually

The Insert row , Add row and Delete row buttons can be used to help build the table
of data. To enter or modify soil information manually, enter the following information in the Soil
– Materials window:

Color The color of a material may be changed by clicking on the colored cell and
selecting one of the pre-defined basic colors or custom-creating a color in
the window that opens.
Soil name The name of the soil can be edited here.
Soil type Select one of the available soil types from the drop-down list: Gravel, Sand,
Loam, Clay or Peat.
Gamma- Enter the (characteristic) dry unit weight of the material (i.e. the unit weight
unsat of the soil when above the water level).
Gamma-sat Enter the (characteristic) saturated unit weight of the material (i.e. the unit
weight of the soil when below the water level).
Friction Enter the (characteristic) angle of internal friction (phi) for the soil. This
angle (phi) value must lie between 0 and 90 degrees.
d50 (median) Enter the (characteristic) median grain size. This column only applies to the
soil types Sand and Gravel. The median size of the soil can influence the
value of parameter αs (NEN 9997-1+C2:2017, Table 7.c and 7.d) which is
used to determine the positive skin friction. The following are the reduction
factors that have been applied for several situation:
⋄ For fabricated piles with closed-end toe in coarse sand of d50 > 600 µm,
the reduction factor for αs is 90% if installed without vibration and 85%
if installed with vibration. The reduction factor for αs in soil grain of
d50 = 2 mm for all condition is 75%.
⋄ For fabricated hollow piles or box piles in coarse sand of d50 > 600 µm
or in clay or loam, the reduction factor for αs is 80% if installed without
vibration and 70% if installed with vibration. The reduction factor for αs
in soil grain of d50 = 2 mm for all condition is 50%.

4.3.1.3 Materials – Match Material

D-F OUNDATIONS offers the possibility to change the properties of an existing material by match-
ing them with the properties of a material from Table 2.b of NEN 9997-1+C2:2017.

First select the material from list of the Soil – Materials window. Then click on the Match
material button to open the Match Material window (Figure 4.5). D-F OUNDATIONS will
propose a list (in the drop down menu) of materials from Table 2.b of NEN 9997-1+C2:2017
with the most likely soil type by matching the cohesion and the friction angle of the current
material. The user can choose either to Copy the NEN parameters or to Keep the current
parameters. When choosing for the first option, only the soil properties will be updated not
the name of the current material.

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Figure 4.5: Match Material window

4.3.2 Profiles
Different actions are possible in the Soil / Profiles node of the tree view:

⋄ section 4.3.2.1 Adding a profile;

⋄ section 4.3.2.1 Modifying an existing profile;
⋄ section 4.3.2.3 Viewing and editing the layers representation of a profile;
⋄ section 4.3.2.4 Entering additional data;
⋄ section 4.3.2.5 Viewing the soil profile;
⋄ section 4.3.2.6 Viewing the pressures profile if available.

4.3.2.1 Adding Profiles

The profiles for a project are displayed as sub-nodes in the tree view, below the node Soil /
Profiles. To add a profile, different options are available:

Add a profile by importing a CPT from file (in CPT, GEF or SON format)
through the Import CPTs from file window.
Create a new profile by manual input of the Top level and Material of each
layer.

Adding Profiles – Import CPTs from file

To import one or more CPTs, right-click the Profiles node and select the Import item. Alterna-
tively, if at least one profile is already present then click on the Profiles node and then select
Import as the Action to be performed.

Note: If there are no profiles yet imported then clicking on the Profiles node will automatically
causes the Import CPTs from file window to open.

The Import CPTs from file dialog that opens allows a file that containing one or more CPTs to
be selected.

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Figure 4.6: Import CPTs from file window

Each CPT that is imported causes a new profile to be added to the list. It is possible to select
more than one file at the time. A number of formats are supported:

⋄ *.CPT:
former D-F OUNDATIONS format, allowing to re-use CPTs used in older versions of D-F OUNDATIONS.
⋄ *.GEF:
Geotechnical Exchange Format, a Dutch standard, developed by CUR, to exchange
geotechnical data such as CPTs.
⋄ *.SON:
an old simple text format for the exchange of CPT-data as used by NENGEO, the pre-
decessor of D-F OUNDATIONS.

Note: New profiles can be added at all times by choosing the Profiles node in the tree view.
When there are no profiles available, just cancel the import dialog that pops up. Otherwise,
the New option is directly available.

Adding Profiles – New

To create an ‘empty’ new profile at the start of a project, cancel the Import CPTs from file
dialog and choose New from the actions on the Soil - Profiles window. This creates an ‘empty’
CPT with an ‘empty’ Profile. In fact, a CPT is created with a qc -value of 0.01 at only two levels
(0 m and -20 m). The belonging Profile has only layer (from 0 m to -20 m) with Undetermined
as material (Figure 4.7).

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Figure 4.7: Soil – Profiles – New CPT window showing ‘empty’ profile

There are two ways to input new layers in the ‘empty’ new profile:

⋄ Manual input of the layers: In the Layers tab of the Soil - Profiles window, add layers
manually using the Add row, Insert row and/or Delete row buttons. For each created
layer, enter its Top level and select the corresponding Material from the drop-down
list (Figure 4.7) containing the soil materials previously defined in the Soil - Materials
window (section 4.3.1): those Materials can either be added from ‘Standard’ or added
manually.
⋄ Manual input of the CPT-values (only in case the CPT-values are known but not avail-
able in one of the following file formats: CPT, GEF or SON): To edit the CPT-values,
select the added node in the tree view. Then right-click the node and choose Edit CPT
Values. This opens the Edit CPT Values window, allowing editing the actual CPT-values
as explained in section 4.3.2.1. Then refer to section 4.3.2.3 for the interpretation of
those CPT-values into a soil profile.

Note: Keep in mind that when working with an inaccurate CPT (which is usually the case in
manually added CPTs) this can influence the accuracy of the calculations too. When working
with an excavation, the CPT-values need to be reduced due to the excavation. With exception
of the manual method, this reduction is a non linear process. When CPTs contain values at
only a few depths, the reduction will be calculated less accurate. However, as the reduction
is larger with inaccurate CPTs this is a safe approach. But remember that with a real CPT, a
better result can be obtained.

4.3.2.2 Options for existing profiles

When right-clicking the node of an existing profile (Figure 4.8), different options are available:

Figure 4.8: Soil / Profiles node, menu

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⋄ Delete to delete the selected profile;

⋄ Rename to modify its name;
⋄ Copy to create a copy of this profile: the entire profile will be copied including the CPT-
values, the layers and the additional data;
⋄ Edit CPT Values to edit the CPT-values (Figure 4.9) and eventually modify the actual
CPT-values;

Figure 4.9: Edit CPT Values window

4.3.2.3 Editing Layers

To view a graphic representation of a CPT, corresponding to its profile, select the correspond-
ing sub-node under the Soil / Profiles node in the tree view. The Layers tab of the Soil – Pro-
files window opens. The red line in the graph corresponds to the qc value, and the blue line
corresponds to the friction. On the right side of the plotted CPT, a soil layer interpretation is
drawn. D-F OUNDATIONS automatically interprets all imported CPTs, based on the interpreta-
tion rule that is selected by the user in the CPT Rule selection box below the graph. To use
the proposed soil layer interpretation, click the button to transport the interpretation into a
profile to be used in the project.

Note: If during the interpretation of a CPT, the point corresponding to the cone resistance and
the friction ratio of a layer is situated outside the limits of the diagram of the selected rule (i.e.
Figure 3.9 in section 3.2.2), the program will assign an Undetermined material to this layer with
unrealistic properties. That’s why the user must always review the automatic interpretation of
the CPT before performing a calculation. In such case, the user must select himself the
appropriate material from the drop-down list of available materials using its expertise.

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Figure 4.10: Soil – Profiles window, Layers tab

CPT Rule Select the interpretation rule used by D-F OUNDATIONS to automatically inter-
pret the imported CPT. Six different rules are available:
⋄ The NEN rule
⋄ The NEN stress dependent rule
⋄ The CUR rule
⋄ The 3-type rule
⋄ The Qc only rule
⋄ The User defined rule
The Qc only rule is especially useful for the interpretation of CPTs that do
not contain information about the friction.
Users may define their own interpretation rules by selecting the last option
in the list of rules: User defined rule. Before using a user defined rule, it
must have been specified in the CPT Interpretation Model window (sec-
tion 3.2.2).
Min. layer All interpretation rules make use of one additional parameter: the minimum
thickness layer thickness, specified in the Min. layer thickness input field below the
selection list. To prevent D-F OUNDATIONS from generating layers that are
too thin to be significant when modeling the problem, the minimum layer
thickness should be increased.
Coordinates As the CPT file does not always contain X and Y co-ordinates, those values
can be entered in the X and Y input fields in the Coordinates sub-window.

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A profile is presented in two ways, both graphically and in a table. The data of the profile can
be entered or changed in two ways:

⋄ by editing data in the table

⋄ by graphically editing the picture in the middle of the window.

Tabular input can be realized by editing the table on the right hand side of the input window.
Use the Insert , Add and Delete buttons next to the table to add or remove layers in
the profile.

The table allows the following changes:

Top Level The top level of each soil layer can be edited manually.
Material Materials can be selected from the list of soil layers that were entered in the
Soil - Materials window.

Soil layers can be added to the profile by clicking the Add boundary button and clicking
anywhere in the graphic representation of the profile to add a layer below that level. Layer
boundaries can be changed dragging them upwards or downwards using the mouse. While
dragging, the level is indicated in a panel below the button bar and the table is updated con-
tinuously.

4.3.2.4 Additional Data

Figure 4.11: Soil – Profiles window, Additional Data tab for Bearing Piles (EC7-NL) model

Under the Additional Data tab, the following information may be entered:

Phreatic level This value specifies the dividing level between the dry soil (above the
phreatic level) and the wet soil (below the phreatic level). The default
value used by D-F OUNDATIONS corresponds to the ground level of the
imported CPT file (GEF, CPT, SON) lowered by 0.5 m.

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Pile tip level Although desirable, it usually turns out that the application of a single
pile tip level within a project is not realistic. Variations in the level of
the bearing layer found in the CPTs force the constructor to apply
several pile tip levels. In the bearing piles model the required pile tip
level can be specified separately for each CPT.
The Preliminary Design, Indication bearing capacity (sec-
tion 4.6.2.1), the Preliminary Design, Pile tip levels and net
bearing capacity (section 4.6.2.3) and the Verification, Design
calculation (section 4.6.3.1) calculation options of D-F OUNDATIONS
suppress the specified Pile tip level and instead performs a series
of calculations over a range of levels defined under Trajectory in the
Calculation window. The other calculation options (section 4.6.2.2)
(section 4.6.3.2) use just the pile tip level specified here in the
Additional Data tab of the Soil – Profiles window.
As default value, D-F OUNDATIONS uses the depth of the CPT point
with the maximum cone resistance raised by 0.8 m in order to get
enough CPT values below the pile tip for CPT interpretation.
Overconsolidation The over-consolidation ratio (OCR) of the bearing layer is normally
ratio of bearing caused by historic loads that were applied to this layer over a
layer long period of time. According to article 7.6.2.3(j) of NEN 9997-
1+C2:2017, the maximum cone resistance should be reduced due
to over-consolidation q
with the formula:
1
qc;z;N C = qc;z;OC × OCR
D-F OUNDATIONS uses 1 default value.
Top of positive Enter the level of the top of the positive skin friction zone. (The bot-
skin friction zone tom of the zone coincides with the pile tip level.) For a pre-fabricated
pile with a widened tip the top of the zone may never be positioned
above the widening (NEN 9997-1+C2:2017 art. 7.6.2.3(c)).
Because there is a strong relation between skin friction and the soil
layer profile, the skin friction zones are constructed from complete
layers. If the top of the positive skin friction zone does not coin-
cide with a layer boundary, D-F OUNDATIONS automatically creates a
dummy layer to force this condition (section 16.7.3). D-F OUNDATIONS
uses the pile tip level as default value.
Bottom of negative Enter the level of the bottom of the negative skin friction zone. (The
skin friction zone top of the zone coincides with the surface or excavation level.)
Because there is a strong relation between skin friction and the soil
layer set-up, the skin friction zones are constructed from complete
layers. If the bottom of the negative skin friction zone does not co-
incide with a layer boundary, D-F OUNDATIONS automatically creates a
dummy layer to force this condition (section 16.7.3). D-F OUNDATIONS
uses the surface level as default value.

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Expected ground The expected ground level settlement determines how negative
level settlement skin friction should be incorporated in the calculations (NEN 9997-
1+C2:2017 art. 7.3.2.2(a)). When the expected settlement is at most
0.02 m, negative skin friction is negligible and will not be considered
at all.
For values ranging from 0.02 m up to and including 0.10 m, the effect
of negative skin friction is directly incorporated into the calculated pile
settlement by adding half of the expected ground level settlement to
the total pile settlement.
For values above 0.10 m, the maximum forces due to negative skin
friction are calculated. These forces are then used to determine the
effect of negative skin friction on the pile settlement.
D-F OUNDATIONS uses 0.11 m as default value in order to enforce the
calculation of the maximum forces due to negative skin friction.
Copy From. . . Click this button to display the Additional Data – Copy from Profiles
window. In this window select the name of one of the profiles and
click OK to copy the additional data given for that CPT into the fields
for this profile.
Copy To. . . Click this button to display the Additional Data – Copy to Profiles
window. In this window select the names of any profiles which should
have the same additional data as defined for the current profile. Click
OK to copy this data to the selected profiles.

4.3.2.5 Viewing Profiles

A graphic representation of the profiles defined for a project can be viewed by clicking one of
the two right most tabs in the Soil – Profiles window:

⋄ The Additional Data tab (Figure 4.12) displays the CPT and, if available, the profile with
data such as defined layers, material types per layer and user defined levels (Phreatic
level, skin friction levels etc.). In addition to the standard qc diagram (red line in Fig-
ure 4.12), the reduced value of qc for the determination of αs (positive skin friction) is
also shown (green line in Figure 4.12) when a valid zone for the positive skin friction has
been defined. Note that the reduction shown here always assumes the use of a driven
prefab concrete pile. The actual reduction as really used in the calculation of course will
be determined by the pile type and the construction method used.
⋄ The Summary Pressures tab (Figure 4.13) also displays the CPT.

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Figure 4.12: Soil – Profiles window, Additional Data tab

Use the buttons in the button bar to manipulate the view.

Note: By right-clicking the mouse button in the CPT/Profile view of the Additional Data tab
and selecting View Preferences, the Project Properties window opens to determine which
names for the soil materials will be used in the profile view.

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4.3.2.6 Summary Pressures

If they are available, the Summary Pressures tab (Figure 4.13) also displays the soil pressures
as derived from the data set in the Soil – Profiles window.

Figure 4.13: Soil – Profiles window, Summary Pressures tab

Use the buttons in the button bar to manipulate the view.

Note: Those pressures are always displayed for the original profile, and the excavations and
surcharges are not taken into account in this view.

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4.4 Foundation
In the tree view, the Foundation node contains the following sub-nodes:

⋄ Pile Types
⋄ Pile Properties
⋄ Top View Foundation

Browsing through these nodes, allows data applying to the foundation to be viewed and input.
The available options are described below.

4.4.1 Pile Types

In the Foundation – Pile Types window (reached by clicking on the Pile Types node), types of
piles can be added and their characteristics defined.

D-F OUNDATIONS is supplied with a database of pre-defined pile shapes. When one of the
pre-defined shapes is selected, a drop down list of pre-defined pile types (depending on the
selected shape) becomes available in the Pile type field. If one of the pre-defined types is
selected, the corresponding pile type data are filled in automatically and cannot be edited.
Select the pile type User defined to enter all data manually.

Figure 4.14: Foundation – Pile Types window for Bearing Piles (EC7-NL) model

The required pile shape can be selected by clicking on the pertinent diagrammatic represen-
tation of the geometry in the panel on the left of the window (Figure 4.14). In the Dimensions
sub-window at the top, the pile dimensions can be entered. The geometric parameters that
are required depend on shape chosen:

Rectangular pile Enter the base width and base length of the pile.
(for piles)

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Rectangular pile Enter the width, length and height of the base, as well as
with enlarged base the width and length of the shaft.

Rectangular pile Enter the base width and base length of the pile.
(for sheet piling)

Round pile Only the diameter is required.

Round tapered pile Enter the diameter at the pile tip and the increase in di-
ameter per m pile length.

Round hollow pile Enter the external diameter and the wall thickness of the
with closed base pile.

Round hollow pile Enter the external diameter and the wall thickness of the
with open base pile.

Round pile with Enter the pile and base diameters and the height of the
enlarged base base.

Round pile with Enter the pile and base diameters. The height of the base
lost tip is automatically set to zero.

Round pile with Enter the pile and base diameters and the height of the
in situ formed base.
expanded base

H-shaped profile Enter the height and width of the H-shape, as well as the
thickness of the web and of the flange.

Note: These dimensions are indicated on the diagrams on the Pile shape sub-window.

When the pile shape is selected, the following information can be entered:

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Pile type Enter the pile type to be defined. D-F OUNDATIONS is supplied with a
database of pre-defined pile types that can be selected from the drop down
list in the Pile type field. The available list depends on the selected pile
shape.
NOTE: For backward compatibility reasons, the pile type "Prefabricated
screw pile with grout" present in norm NEN 9997-1:2009 is still present
in the program eventhough it is no longer mentioned since the norm
NEN 9997-1:2016. This pile type is kept so users are able to recalculate
their old projects using this type. It is therefore advised not to use this type
in new projects.
NOTE: Both pile types "Straight timber pile" and "Steel section" are consid-
ered to be low vibrating even though they are driven and/or vibrated into
place. This is due to their being very easily driven/vibrated into the soil and
thus do not generate lots of vibration.
Use Per 1 january 2016, all αρ values must be reduced by 30 percent (as given
Pre in article by Van Tol/Hannink in 2015; not the 33 percent as given in NEN-
2016 EN 9997-1:2012). For backward compatibility reasons, it is possible to se-
lect the "Use Pre 2016" option.
αs αs is the pile factor for the shaft friction. The value for the factor, according
to NEN 9997-1+C2:2017, depends on the soil material for cohesive soils:
⋄ For non-cohesive soils (sand, gravel) the value for αs depends on the
pile type. Therefore it can be specified by selecting one of the standard
pile types from the combo box. As a result the actual value for αs will be
displayed in the current value box. If User defined is selected as the sub-
type, only the parameter value is entered; the relation of the subtype with
the pile type no longer applies. This has the following consequences:
The value entered for αs , valid for sand and gravel layers, will NOT
⋄

be adjusted for any instance of coarse grain (NEN 9997-1+C2:2017

Table 7.c)
The exception for the determination of the pile tip shape factor β
⋄

cannot be met because it is impossible to determine that a cast-in-

place pile with a regained steel driving tube is applied (NEN 9997-
1+C2:2017 art. 7.6.2.3(g)).
The check on ∆L (length of positive skin friction zone) when
⋄

a weighted tip is applied cannot be performed because it can-

not be determined that a pre-fabricated pile is used (NEN 9997-
1+C2:2017 art. 7.6.2.3(c)).
⋄ For cohesive soils (clay, peat, loam) the factor according to the standard
is depth-dependent and thus has no single value.
As a result the current value box displays N.A. (Not Applicable) as the
value can not be shown. If User defined is selected as the subtype, only
the parameter value is entered. That value can and will be displayed as
current value.
NOTE: According to NEN 9997-1+C2:2017 Table 7.d, this factor for ‘Very
sandy loam’ is equal to the percentage of friction Rf measured by an elec-
trical CPT, with a maximum of 0.025. As this measured parameter is not
always available from the CPT data, D-F OUNDATIONS always uses the limit
value of 0.025.

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αp αp is the pile factor for the pile point. As αs for sand/gravel, αp depends on
the pile type for its value. Therefore it can be specified by selecting one of
the standard pile types from the combo box. As a result the actual value for
αp will be displayed in the current value box. Select User defined to specify
another value for αp .
If User defined is selected for αp , the pile factor for the pile point, then the
exception for ‘continuous flight auger’ piles cannot be taken into account
for the reduction of qc -values when determining qc;III;mean . The reason for
this is that it cannot be determined if a continuous flight auger pile is used
(NEN 9997-1+C2:2017 art. 7.6.2.3(e)).
Load Because the Load-Settlement curves (NEN 9997-1+C2:2017, Figures 7.n
settlement and 7.o) contain only lines for three subtypes, in D-F OUNDATIONS too the
curve choice is limited to these three subtypes: 1, 2 or 3.
As Prefab Only visible for user-defined pile type. If this checkbox is marked, the user-
defined pile type is considered to be prefabricated, otherwise it is consid-
ered to be formed in the ground. This choice will have an influence on the
characteristic value of the negative skin friction Fnk;k , more precisely on the
value of the friction angle between pile shaft and ground (δj;k ). Refer to
7.3.2.2(d) of NEN 9997-1+C2:2017 for more information.
Reduce Only visible for user-defined pile type. If this checkbox is marked, the en-
qc;III by [%] tered percentage of reduction will be applied on qc;III;mean for the calcula-
tion of the maximum point resistance qb;max (art. 7.6.2.3(e) of NEN 9997-
1+C2:2017). The default reduction is 25% which means that the user wants
a result of 75% of the original qc;III -value.
NOTE: As it concerns qc;III , this reduction will have no effect on the calcu-
lation if in the Model options sub-window (Figure 4.23) the user chooses to
suppress the reduction on qc;III by marking option Suppress qc;III reduction.
Material & In the Material field select the material of the user defined pile. The cor-
Young’s responding elasticity modulus is provided automatically for concrete, steel
modulus and timber and cannot be edited. If the material "User defined" is selected
then the Young’s modulus must also be entered.
Slip layer & In the Slip layer field select a slip layer for the pile, if one is to be used.
Characteristic The corresponding characteristic adhesion is provided automatically and
adhesion cannot be edited, unless the value User defined is selected, in which case
the required Characteristic adhesion should be input.
Pile tip cross If this checkbox is marked, a user defined value for the Pile tip cross section
section factor (s) can be specified. If left unmarked, the value will be determined
factor (s) according to the NEN 9997-1+C2:2017.
Pile tip If this checkbox is marked, a user defined value for the Pile tip shape factor
shape factor (β ) can be specified. If left unmarked, the value will be determined accord-
(β ) ing to the NEN 9997-1+C2:2017.

Note: For pile type Open ended steel pipe with plugging two calculations are made, one with
plugging effect (Shaft friction only on the outside of the pile, pile point considered closed) and
one without the plugging effect (Shaft friction on the outside and the inside of the pile, pile
point considered open). The least favorable result is automatically taken into account.
Moreover, the pile tip factor s, that accounts for the influence of the shape of the cross-section
of the pile base, has a different value in both plugging situations:

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– for plugged situation, as the largest (b) and smallest (a) dimensions of the cross section
are equal, factor s is 1.
– for unplugged situation, formula given in art. 7.6.2.3(h) of NEN 9997-1+C2:2017 leads
to:
sin φ
1+
b/a
s= = 0.61 with φ = 40◦ , a the wall thickness and b the diameter.
1 + sin φ

Building a pile type database

Pile type definitions created in the Foundation – Pile Types window can be saved to a FOP file
by means of the Export option, reached by right clicking the Pile Types node in the tree view
and selecting Export from the context menu, or left clicking on the Pile Types node and then
selecting Export in the Action sub-window of the Foundation – Pile Types window. This allows
a database of pile types to be built up which can be used in future projects, allowing the pile
type definition with less effort and less chance of errors. Use the Import option in the same
context menu to select a previously saved FOP file for the pile type currently selected. When
the appropriate file has been located and opened, the pile types in the FOP-file are added as
new nodes under the Pile Types node.

4.4.2 Pile Properties

Use the Foundation – Pile Properties window to define the positions of the piles and the loads
for the project. There are several ways to do this, as described hereafter.

Figure 4.15: Foundation – Pile Properties window for Bearing Piles (EC7-NL) model

In this window the following information can be entered:

Name In this box the pile position names are displayed. Each position automati-
cally receives a number when added to the list. The name can be changed
if desired.

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X Enter the X coordinate of the position of the center of the pile. The same
coordinate system must be used as when entering the CPT coordinates.
Y Enter the Y coordinate of the position of the center of the pile. The same
coordinate system must be used as when entering the CPT coordinates.
Pile head The pile head level is used to specify for each pile the level of the pile head
level with regard to the reference level (usually NAP – the Dutch reference zero
level). This allows calculation with deepened pile heads (i.e. below the
ground level). If the pile head level is not entered the default level (0.00 m
NAP) applies.
Surcharge Here the value of a surcharge (or superimposed load) immediately next to
the pile can be entered. This value needs be specified only if the load is
permanent. If an excavation must also be taken into account, the surcharge
is assumed to apply at excavation level. In all other cases it is assumed to
apply at surface level.
In the theory part of the manual, more information can be found about mod-
eling superimposed loads (Combination of Superimposed load/Excavation,
section 16.7.5).
Limit state The load on the piles (Fs;d ) can be specified for both STR/GEO and ser-
STR/GEO viceability limit states. The values for Fs;d (STR/GEO) and Fs;d (service-
ability) are derived by multiplying the characteristic loads of the building on
Serviceability the pile foundation with the corresponding load factors which need deter-
limit state mined according to NEN 9997-1+C2:2017 appendix A. Usually the calcu-
lation values to be entered here are determined by the constructor of the
building. For more information on limit state STR/GEO and serviceability,
see NEN 9997-1+C2:2017 art. 2.4.7 & 2.4.8.

Use the toolbar on the left side of this window to edit the table:

Use this button to insert a row in the table.

Use this button to add a row to the table.
Use this button to delete a row from the table.
Use this button to generate a grid of piles with the same properties (see below).
Use this button to change the properties (Pile head level, Surcharge, Design values
of load on pile) of all the pile positions (see below).
Use this button to cut a selected part of the table.
Use this button to copy a selected part of the table.
Use this button to paste a selected part in the table.

Click the fourth button in Pile Properties window to open a window in which a grid of pile
positions can be specified.

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Figure 4.16: Pile Grid window for Bearing Piles (EC7-NL) model

The pile properties can also be entered in the Pile Grid window. This results in the same
properties for all pile positions in the grid, but, if required, these properties can later be edited
individually.

In the Pile Grid window the following information can be entered:

Start at Enter the start coordinates for the center of the bottom-left pile in the
grid. The same coordinate system must be used as when entering the
CPT coordinates. To help with setting the positions of the piles relative
to the used profiles/CPT’s, the option Set relative to profile can be used
to select a profile of which the coordinates will be used as base for the
pile plan.
Centre to centre Enter the distance between the pile centers.
distance
Number of piles Enter the number of piles in each direction.
Parameters For more information see the descriptions for the Foundation – Pile
Properties window above (section 4.4.2).
Use pile grid to Enable this check box to replace the existing pile positions in the project
replace current with those defined by the grid. If this check box is left empty, the posi-
pile positions tions in the pile grid will be added to the existing pile positions.

Click the fifth button in Pile Properties window to open the Edit properties for all positions
window (Figure 4.17) in which the Pile head level, Surcharge and Design values of load on
pile of all pile positions can be edited and/or modified. If modified, the properties of all pile
positions will automatically be updated in the corresponding column of the Pile Properties
window (Figure 4.15).

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Figure 4.17: Edit properties for all positions window for Bearing Piles (EC7-NL) model

4.4.3 Top View Foundation

Select Top View Foundation under the Foundation node in the tree view to display this window.
Here the pile locations and types and the CPTs can be seen in plan view for a selected Pile
type. In case of pile group, the collection of Middle piles (blue bullet in the Legend, see
Figure 4.18) shows the piles that could possibly be part of a pile group for the determination
of the negative skin friction (NEN 9997-1+C2:2017, art. 7.3.2.2(e)). The collection of Edge
piles (black bullet in the Legend, see Figure 4.18) shows the rest of the piles which are not
part of the pile group for the determination of the negative skin friction.

Figure 4.18: Foundation – Top View Foundation window for Bearing Piles (EC7-NL)
model

The button bar of this window allows the view to be manipulated in various ways:

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Click this button to select objects using the cursor and to finish using any of the
other modes described below.
Click this cursor to activate the pan mode. Click and drag the view to see a different
part of it.
Click this button to activate the zoom-in cursor. Then click on the part which is to
become the centre of the desired enlarged view. Repeat this step several times if
necessary.
Click this button to undo the last zoom-in step. If necessary, click several times to
retrace each consecutive zoom-in step that was made.
Click this button to select a rectangle for enlargement. The selected part will be
enlarged to fit the window. Repeat this step several times if necessary.
Click this button to measure the distance between two points. Click on one point
and the distance from there to the current mouse position is displayed in the panel
at the bottom of the view.
Click this button to undo the last zoom step.
Click this button to restore the original dimensions of the view.

4.5 Excavation
Click the Excavation node in the tree view to display this window. Here, one Excavation level
can be entered for all soil profiles. Under Reduction of cone resistance select the method by
which the cone resistance is to be reduced, in order to take the effect of the excavation into
account.

Figure 4.19: Excavation window

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Manual reduction of cone resistance

The reduction percentages per layer per CPT can be specified by the user by selecting Man-
ual, selecting the relevant CPT, and then entering the reduction percentages qc Reduction for
the Top Level of each soil layer. For the selected CPT the reduction will take place via:

(100 − red%)
qc;red = qc × (4.1)
100

Safe (NEN) reduction of cone resistance

If Safe (NEN) is selected under Reduction of cone resistance, all CPTs are reduced in a very
safe manner in accordance with NEN 9997-1+C2:2017 art. 7.6.2.3(k). This implies complete
relaxation of the soil beneath the excavation as well as an infinite width of the excavation.

Begemann reduction of cone resistance

This method also reduces all CPTs at once. It takes into account the proximity of the edge of
the excavation to the construction. The distance to this edge can be varied in the Distance
edge pile to excavation boundary field. Note that this distance is the distance between the
excavation edge (left and right of the pile plan) and the center of pile(s) on the outside of
the pile plan (the so called edge piles as these are on the left respectively right edge of the
pile plan). To see the excavation, click Top View Foundation in the tree view to display the
pile plan. The effect of the excavation (reduction of the cone resistance) can be viewed per
CPT in the drawing on the left of the Excavation window. The drawing also displays the effect
in terms of stresses. The initial effective stress shows the stress without excavation. The
effective stress shows the stress after excavation.

Reduced cone resistance values

It is possible to view the reduced values for the cone resistance by clicking the right mouse
button in the drawing area of the excavation window. This will pop up a menu offering to view
these values as shown in Figure 4.20.

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Figure 4.20: Excavation window, pop menu for viewing reduced values

Clicking the option will display the table as shown in Figure 4.21 with the depth, the original
value and the reduced value. By clicking in the index column and dragging the down (or up)
you can select rows to copy from the table (for instance to Excel). You can either use the
provided Copy button or use CTRL-C.

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Figure 4.21: Reduced CPT values table

4.6 Calculations
To start a calculation, click the Calculation node in the tree view or select Start in the Cal-
culation menu. A window opens with various options to be set and the types of calculation
available. The top half of the window relates to data required for bearing pile calculations
(described in section 4.6.1), whilst the bottom part of the window is related to the selection of
the type of calculation to be performed (described in section 4.6.2 to section 4.6.3.2).

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Figure 4.22: Calculation window for Bearing Piles (EC7-NL) model

4.6.1 Options for a Bearing Piles (EC7-NL) calculation

Before performing calculations on the project design, a number of options can be specified
that will apply to all bearing piles.

Note: Some of the options are found in the sub-window Overrule parameters. This allows
certain parameters to be overruled which otherwise would be determined according to the
standard (or would be calculated, in case of the negative skin friction area). The user must
make sure that an overruling of parameters is allowable. These parameters must be used
with the utmost caution.

Figure 4.23: Calculation window, Options for Bearing Piles (EC7-NL) model

In the top part of the window the following information can be entered:

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Rigidity of Here the superstructure can be specified as either Non-rigid or Rigid ac-
superstructure cording to NEN 9997-1+C2:2017 art. 7.6.1.1(c).
A restriction for the schematics is that for each calculation only (parts of)
buildings that can be regarded as either “completely rigid” or “completely
non-rigid” can be included in one schematic. If a building is regarded as
partly “rigid” and partly “non-rigid” (for instance a building with a rigid core)
at least two calculations must be carried out: one for the rigid part and one
for the non-rigid part. Also if a building consists of several parts that can
be regarded as rigid, a calculation must be made for each part. The rea-
son for this restriction is the impossibility of determining the relevant inter-
nal distances within the pile plan. Therefore the internal rotations between
rigid and non-rigid foundation elements cannot be calculated correctly. The
choice between Rigid and Non-rigid influences the calculation in various
ways: the factor ξ3 and ξ4 depends on it, as does the calculation method
for the bearing capacity, settlement and rotations.
Maximum The values given in NEN 6740:1991 are provided as the default settlement
allowed demand for which verification takes place. The values of NEN 6740:1991
settlement are used because the standard NEN 9997-1+C2:2017 does not specify the
maximum values for allowed settlement. It is possible to edit these values
for either of the two limit states. In case of limit state EQU/GEO, the default
is an advised value whereas for serviceability limit state the default should
be considered a minimum value. If the values do not match the defaults this
will be explicitly mentioned in the report.
Maximum The values given in NEN 9997-1+C2:2017 are provided as the default rel-
allowed ative rotation demand for which verification takes place. It is possible to
relative edit these values for either of the two limit states. In case of limit state
rotation EQU/GEO, the default is an advised value whereas for serviceability limit
state the default should be considered a minimum value. If the values do
not match the defaults this will be explicitly mentioned in the report.
ξ4 Here the value for ξ4 (the correlation factor for the minimum value of calcu-
lated pile resistances) can be overruled. This factor depends on the rigidity
of the superstructure and number of CPTs (see Tables A.10a and A.10b in
NEN 9997-1+C2:2017).
γb Here the value for γb (the partial resistance factor for pile tip) can be over-
ruled (see Tables A.6, A.7, and A.8 in NEN 9997-1+C2:2017).
γs Here the value for γs (the partial resistance factor for pile shaft in com-
pression) can be overruled (see Tables A.6, A.7, and A.8 in NEN 9997-
1+C2:2017).
γf ;nk Here the value for γf ;nk the safety factor for the negative skin friction,
can be overruled. Normally this factor would be derived as prescribed in
NEN 9997-1+C2:2017 art. 7.3.2.2(b). If overruled, this factor will be used
for both GEO and SLS checks.
Note: A negative factor can be entered (valid range goes from -100 to 100).
Note: For SLS, the program will automatically limit the factor γf ;nk to 1 dur-
ing the calculation.
Area Here the influence area per pile, to be used within the calculation of the
negative skin friction for pile groups, can be defined by the user. If this
option is not used the program itself will determine the influence area. This
is done by calculating the average pile distance within the pile group (Davg )
and then setting the area to Davg × Davg .

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Eea;gem Here the value for the average soil modulus can be overruled. This modu-
lus would normally be calculated according to NEN 9997-1+C2:2017, art.
7.6.4.2(k) (i.e. mean modulus of elasticity of the soil beneath the level of
4D under the pile point). Refer to section 16.5 for more information.
qb;max Here the value for qb;max (the maximum allowed point bearing capacity)
can be overruled. Normally this would have a fixed value of 15 MPa as
prescribed in NEN 9997-1+C2:2017, art. 7.6.2.3(e).
qc;z;a (low) Here the value for qc;z;a (low) (the lower boundary at which qc-values need
to be truncated for the determination of maximum allowed shaft bearing
capacity) can be overruled. Normally this would have a fixed value of 12
MPa as prescribed in NEN 9997-1+C2:2017, art. 7.6.2.3(i).
qc;z;a (high) Here the value for qc;z;a (high) (the higher boundary at which qc-values
need to be truncated for the determination of maximum allowed shaft bear-
ing capacity) can be overruled. This higher value is only applicable for lay-
ers thicker than 1 m where all qc-values are at least as large as the higher
boundary. Normally this would have a fixed value of 15 MPa as prescribed
in NEN 9997-1+C2:2017, art. 7.6.2.3(i).
Write Intermediate results can be written to a file by selecting this checkbox. It
intermediate must be born in mind that such a file can become very large.
results NOTE: This file is only available in Dutch.
Use pile In NEN 9997-1+C2:2017 the calculation of the negative skin friction de-
group pends on whether the piles are to be considered as one (or more) pile
group(s). When piles are within 5 m of each other, the piles form a pile
group. Piles with no other piles within this 5 m radius are considered to be
single piles.
If a pile group exists, calculations for negative skin friction usually take the
pile group into account. If this is not desired, disable this checkbox. The
reason for this option is that, depending on the pile plan, negative skin
friction calculations can take the pile group model for negative skin friction
(NEN 9997-1+C2:2017, art. 7.3.2.2(e)) into account. This does not always
yield favorable results, especially when the single pile model (NEN 9997-
1+C2:2017, art. 7.3.2.2(d)) is applied and a γf ;nk value of 1.0 (single pile)
instead of 1.2 (pile group) can be used for limit state GEO (NEN 9997-
1+C2:2017, art. 7.3.2.2(b)).
Overrule If this checkbox is enabled, the excavation will not be taken into account.
excavation
Suppress When using continuous flight auger piles, a reduction of qc;III;gem needs to
qc;III be applied. In that case the qc -values for determining qc;III;gem are limited
reduction to a maximum of 2 MPa. According to NEN 9997-1+C2:2017 art. 7.6.2.3(e),
this reduction can be left out if the CPT has been carried out at a distance
of 1 m from the pile, after the pile has been placed. D-F OUNDATIONS there-
fore contains the option to suppress this reduction. Literally speaking the
reduction can only be left out if after installation a CPT is made for each pile
at a distance of at most 1 m. As this interpretation is very strict and costly,
the user is advised to consult the inspection regarding the required number
of CPTs in order to meet this requirement. If the reduction is suppressed,
this fact is explicitly mentioned in the output file.

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Use Almere Due to the special nature of the soil conditions in the Dutch city of Almere,
rules experience in making pile foundations has lead to a more strict approach to
calculating these foundations (Almere, 2016). Select this checkbox to apply
this approach to the project.
This more strict approach consists of the following:

⋄ The contribution of the bearing capacity, produced by the shaft friction

per CPT (Rs;max;i ), to the total bearing capacity for each CPT must
be limited to at most 75% of the contribution provided by the pile point
(Rb;max;i ):
Rs;max;i ≤ 0.75 × Rb;max;i
⋄ According to article 3.2.3(e) of NEN 9997-1+C2:2017, the average
distance agem of the CPT’s is limited by amax , which depends on the
variation of the underground:

If ∆Rc;cal ≤ 0.3 Rc;cal;gem , then amax = 25 m

⋄ ⋄ ⋄

If ∆Rc;cal ≤ 0.4 Rc;cal;gem , then amax = 20 m

If ∆Rc;cal > 0.4 Rc;cal;gem , then amax = 15 m

Use In a small special area of Almere, the conditions are even worse which
additional results in a additional rule when working in this area:
Almere rule If ∆Rc;cal ≥ 0.5 Rc;cal;gem , then amax = 10 m.

4.6.2 Preliminary Design for Bearing Piles (EC7-NL)

D-F OUNDATIONS allows a preliminary design to be calculated. Three different preliminary de-
sign calculation types are available:

⋄ Indication bearing capacity outlined in section 4.6.2.1;

⋄ Bearing capacity at fixed pile tip levels outlined in section 4.6.2.2;
⋄ Pile tip levels and net bearing capacity outlined in section 4.6.2.3.

Note: Preliminary design always considers single piles.

Firstly the type of calculation can be selected. Some types require additional data. Next the
CPTs and pile types to be included in the preliminary calculations are selected. Note that the
order in which the items are selected determines the order of calculations. More detail about
the selection process for the different preliminary design types is given in section 4.6.2.1,
section 4.6.2.2 and section 4.6.2.3.

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Figure 4.24: Calculation window, Preliminary Design for Bearing Piles (EC7-NL) model

Finally, once the calculation type and relevant parameters have been selected, click Start to
begin the calculation.

Note: When a calculation is started, any previous calculation results will be replaced. To
retain previous results, print the results or make a copy of the project files. Alternatively, set
the default action to Always Save As instead of Always Save for the Save on Calculation
option on the General tab in the Program Options window (Tools menu). In that case a ‘Save
As’ dialog will automatically appear each time a calculation is started.

Note: The nature of the calculation that has to be performed greatly influences the time
needed to perform the calculation. Apart from the number of piles (when performing verifica-
tion) and the number of selected CPTs and Pile types, there is another factor that has great
impact upon the required calculation time: if positive friction has to be calculated, the required
calculation time may increase considerably. This is especially true if the positive friction zone
contains cohesive soil types (loam, clay, peat) in which case the calculation time may increase
a hundredfold or more.

Note: When a Begemann reduction of cone resistance values is applied in the Excavation
window (section 4.5), a pile in the middle of the excavated area (see pile 2 in Figure 4.25)
will have a stronger reduction as opposed to a pile at the border of the excavation. For
a Verification calculation, D-F OUNDATIONS will calculate this reduction considering the proper
input. However, for a Preliminary Design calculation, only one pile is relevant in the calculation.
Therefore, this will translate to:

⋄ on the left of the single pile, the distance is the same as the Distance edge pile to
excavation boundary inputted in the Excavation window;
⋄ on the right of the single pile, D-F OUNDATIONS assumes that the distance from the edge
pile to the excavation boundary is very big so the edge does not have any influence.

Therefore, in the case schematized in Figure 4.25, pile 2 will have a lower (so incorrect)
reduction for a Preliminary Design calculation than for a Verification calculation. To avoid
this the user should make sure that, during a Preliminary Design calculation, the Distance
edge pile to excavation boundary inputted in the Excavation window is the same as the real
minimum distance edge pile to the excavation boundary of the single pile (called Dmin;2 in
Figure 4.25). The user should also make sure that its maximum distance (called Dmax;2 in
Figure 4.25) is set to a large value to simulate an endless excavation on the other side of
the pile. Following this procedure, the Preliminary Design calculation is sure to give slightly
lower (so safer) bearing capacities than the Verification calculation (based on the pile plan
with excavation boundaries on both sides). This way, the chance is larger that the Preliminary

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Design calculation will pass the Verification calculation.

Figure 4.25: Schematization of the Begemann reduction of cone resistance for a Verifi-
cation and a Preliminary Design calculation

4.6.2.1 Preliminary design: Indication bearing capacity

This option is used to obtain an indication of the (net) bearing capacity in relation to different
pile tip level(s).

Instead of the specified pile tip levels per CPT, a pile tip trajectory is used. This trajectory is
determined by means of a top and bottom limit in m above or below the reference level (usually
NAP). The interval of the trajectory determines the number of calculations to be performed,
with a maximum of 151. The bearing capacity is calculated at each pile tip level specified in
the trajectory.

When defining a trajectory the user need not take account of the specified levels of posi-
tive and negative skin friction in the Additional Data tab of the Soil - Profiles window (sec-
tion 4.3.2.4). If required (for example if the top of positive skin friction zone is below the pile
tip level), these levels are adjusted automatically by D-F OUNDATIONS for each calculation step.

Both the top and bottom limits of the trajectory must meet a number of requirements. The top
limit value (Begin) must be chosen in such a way that the minimum pile length in the ground is
5 × dmin (dmin = the smallest cross measurement of the pile tip cross section). This means
the Begin value must be at least 5 × dmin below the lowest surface level, excavation level and
pile head level. A Begin value above these levels means that the pile is not a pile according to
NEN 9997-1+C2:2017 art. 1.5.2.128. The bottom limit value (End) must be at least 4 × Deq

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(Deq = equivalent diameter) above the deepest level of the shallowest CPT.

This requirement follows necessarily from the calculation model for the bearing capacity
(Koppejan). A deeper bottom limit would make correct calculation impossible. The Inter-
val must be chosen in such a way that a maximum of 151 calculations will be performed.
If the above requirements are not met, D-F OUNDATIONS will not perform a calculation but will
suggest better values to be used.

The result of the preliminary calculation is the net bearing capacity (Rc;net;d ) for each CPT as
a function of the pile tip level. The results are displayed in tables per pile type as well as in a
graph. Rc;net;d is an inferred entity which does not appear in the standard. It is defined as:

Rc;net;d = Rc;max;d − Fs;nk;d (4.2)

The calculation value of the maximum bearing capacity (Rc;max;d ) for each CPT is also an
inferred value and is as such not included in the standard. In the standard the calculation
value of the bearing capacity is determined for each examined foundation and not for CPTs
individually.

The results for each trajectory level are presented in a table as well as in a graph. Both the
table and graph can be viewed with the Design sub-node in the Results node. For more
information on viewing results, refer to chapter 7.

4.6.2.2 Preliminary design: Bearing capacity at fixed pile tip levels

This option is used to obtain an indication of the (net) bearing capacity in relation to the pile
tip level of each CPT.

The result of this calculation is the maximum bearing capacity (= point resistance + shaft
friction) for each CPT. The calculation value of the maximum bearing capacity (Fr;max;d ) for
each CPT is an inferred value and is as such not included in the standard. In the standard the
calculation value of the bearing capacity is determined for each examined foundation and not
for CPTs individually.

Also the correct negative skin friction is calculated for each CPT, which allows the user to de-
termine the net bearing capacity (Rc;max;d - Fs;nk;d ) for each CPT. The results are presented
in a table. The table can be viewed with the Design sub-node in the Results node. The results
can also be found in the report (Report sub-node). In the report an additional table presenting
the Rc;net;d per pile type per CPT can be found. For more information on viewing results see
chapter 7.

4.6.2.3 Preliminary design: Pile tip levels and net bearing capacity
This option is used to obtain an indication of the required pile tip level per CPT in order to re-
alize the desired net bearing capacity (Rc;net;d ). This desired net bearing capacity can be re-
garded as the desired maximum allowable calculation load on the pile in limit state STR/GEO
and as such does not appear in the standard.

The required pile tip level per CPT is located in a user-defined pile tip trajectory. This trajectory
is specified by means of a top (Begin) and bottom (End) limit in m above/below the reference
level (usually NAP in the Netherlands). The Interval of the trajectory determines the number
of calculations to be performed, with a maximum of 151. Information about the requirements
that must be met when defining the trajectory can be found in section 4.6.2.1.

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When defining a trajectory the user need not take account of the specified levels of posi-
tive and negative skin friction. If required, these levels are adjusted automatically for each
calculation step.

Together with the trajectory definition the required Net bearing capacity (Rc;net;d ) must be
entered. This value is used as a stopping criterion for the calculation. As soon as a level
has been detected for a CPT where the calculated net bearing capacity (Rc;net;d ) equals or
exceeds the required net bearing capacity, the calculation for that CPT is aborted after which
the calculated capacities are displayed. Rc;net;d is again an inferred entity which does not
appear in the standard, and is defined as follows:
Rc;net;d = Rc;max;d − Fs;nk;d (4.3)
If within the trajectory no level is found for a CPT with the required net bearing capacity, this
is marked as ’******’ in the Level column. In order to provide some idea of how large the
insufficiency is, the calculated capacities for the last trajectory level are included.

The table can be viewed with the Design sub-node in the Results node. The results can also
be found in the report (Report sub-node). In the report an additional table presenting the
Rc;net;d per pile type per CPT can be found. For more information on viewing results, refer to
chapter 7.

4.6.3 Verification for Bearing Piles (EC7-NL)

This function provides two verification options: Design calculation and Complete calculation.
The options for these calculations are outlined in section 4.6.3.1 and section 4.6.3.2 respec-
tively. The CPTs and pile type to be used in the calculation should also be selected here.
Contrary to the preliminary design options the calculations are complete and include settle-
ments and rotations. The complete pile plan is also considered, taking care of group effects.
Note that only one pile type can be used per verification. The CPT test level is used to perform
a separate calculation of the bearing capacities of all CPTs at that level. These bearing capac-
ities are then used to check the compliance with the demands as set by NEN 9997-1+C2:2017
art. 3.2.3(e) regarding the number of CPTs and their spacing.

Figure 4.26: Calculation window, Verification for Bearing Piles (EC7-NL) model

Once all selections have been made, click Start to begin the calculation.

Note: When a calculation is started, any previous calculation results will be replaced. To
save previous results, print the results or make a copy of the project files. Alternatively, set the
default action to Always Save As instead of Always Save for the Save on Calculation option
on the General tab in the Program Options window (Tools menu). In that case a ‘Save As’
dialog will automatically appear each time a calculation is started.

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Note: The nature of the calculation that has to be performed greatly influences the time
needed to perform the calculation. Apart from the number of piles (when performing verifica-
tion) and the number of selected CPTs and Pile types, there is another factor that has great
impact upon the required calculation time: If positive friction has to be calculated, the required
calculation time may increase considerably. This is especially true if the positive friction zone
contains cohesive soil types (loam, clay, peat) in which case the calculation time may increase
a hundredfold or more.

4.6.3.1 Verification: Design

This option allows a calculation to be performed while at the same time verification for all limit
states (EQU, GEO, and serviceability) is carried out. To be able to perform such verifications,
the design loads on the piles must have been specified in the sub-node Pile Properties of the
Foundation node.

Instead of the specified pile tip levels per CPT, a pile tip trajectory is used. This trajectory is
specified by means of a top (Begin) and bottom (End) limit in m above/below the reference
level (usually NAP). The Interval of the trajectory determines the number of calculations to be
performed, up to a maximum of 151.

When defining a trajectory the user need not take account of the specified levels of positive
and negative skin friction. If required, these levels are adjusted automatically for each calcu-
lation step. It must be born in mind, however, that the defined trajectory will be the same for
all CPTs. A given pile tip level in the trajectory is used for all CPTs during the calculation step.
This trajectory approach differs from the calculations performed with the Complete calculation
option (section 4.6.3.2).

When interpreting the design results the user must be aware of the possible complications
caused by using a pile tip trajectory for all CPTs, especially if strongly receding CPT values
occur for several CPTs in the calculation area. An example would be a situation with a soft
layer varying in height for each CPT. In that case there is a reasonable chance that the design
calculation will indicate that no trajectory level meets the requirements. At each level the
soft layer (with the corresponding low CPT values) is manifest in one of the CPTs, which will
influence the calculation results negatively. The fact that a design calculation does not contain
a level that meets the requirements does not mean that these requirements cannot be met at
all (see Complete calculation in section 4.6.3.2). It does show, however, that it is impossible
to maintain a single pile tip level for all CPTs.

For more information about the requirements for the Begin and End values of the trajectory,
please refer to "Indication bearing capacity" (section 4.6.2.1]. It must be noted that according
to NEN 9997-1+C2:2017 art. 3.2.3(e) the End value must be at least 5 m above the deepest
level of the shallowest CPT. Moreover, the same article specifies that the End value must be
at least 10 × dmin above the deepest level of the deepest CPT. An End value below this level
does not meet the requirements as set by the standard. When such a value is entered the
output file will contain a warning that the defined trajectory does not meet the requirements
as set by the standard. However, calculations based on levels that are too deep will still be
carried out.

The result of this calculation is the maximum bearing capacity for the foundation as a function
of the pile tip level. Based on the entered loads the foundation will be checked to see if it meets
the settlement and rotation requirements in both the limit states EQU/GEO and serviceability
limit state.

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For information on viewing results see chapter 7.

4.6.3.2 Verification: Complete

This option allows a complete verification to be performed according to the NEN 9997-1+C2:2017
standard. All required calculations (bearing capacity, settlement and negative skin friction) are
carried out according to these standards.

For a complete verification, the user can specify a different pile tip level for each CPT and
consequently a soft layer with varying height will not have the same effect as described in the
section on Verification, Design calculation (section 4.6.3.1). This increases the chance that
the required standard will be met.

The results are presented in the report which can be accessed by clicking the Report sub-
node in the Results node. For more information about viewing results, refer to chapter 7.

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Two types of data are required to perform a calculation using D-F OUNDATIONS:

⋄ Firstly, data needs to be input in order to determine the soil behavior. This data in-
cludes CPTs with their corresponding soil profiles, including the ground water level, the
expected ground level settlement, and so on. This data is entered in the windows that
appear when selecting the sub-nodes below the Soil node in the tree view.
⋄ Secondly, data is required to specify the construction (of the foundation), e.g. pile type,
pile dimensions, pile plan, and so on. The relevant options can be found in the windows
that appear when selecting the sub-nodes below the Foundation node in the tree view.

Before calculating the project design, a number of options need to be specified that will apply
to all piles in the window that appears when the Calculation node is selected in the tree view.

5.1 Tree view

Figure 5.1: Main window for the Tension Piles (EC7-NL) model

For the Tension Piles (EC7-NL) model, the tree view contains the following nodes and sub-
nodes:

Project Properties / Use this option to describe and identify the project.
Description
Project Properties / Use this option to specify the execution time of CPTs relative to the
Construction pile installation and any excavation. This information is needed to
Sequence determine whether the problem qualifies for certain exceptions made
in NEN 9997-1+C2:2017.
Soil / Materials Use this option to enter the soil material properties.
Soil / Profiles Use this option to enter and view a soil profile for each CPT, as well
as to enter additional data related to the CPT.
Foundation / Use this option to enter the required pile types. The pile type and its
Pile Types dimensions are specified here.

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Foundations / Use this option to define the pile plan. Apart from the pile positions,
Pile Properties the pile head level, a superimposed load next to the pile (if required)
and of course the pile load are entered. This data can be input by
entering information for each pile separately or by generating a grid
of piles at once.
Foundations / Top Use this option to see a graphic representation of entered piles and
View Foundation CPTs.
Excavation Use this option to specify the excavation level, along with some addi-
tional parameters related to modeling the excavation.
Calculation Use this option to specify the calculation settings and verification re-
quirements, and to execute the actual calculation.
Results / Load- Use this option to view the load-rise curves as part of the results
Rise Curve of verification option. Only when such a verification calculation has
been performed, these curves are available. The results will be pre-
sented as graphs.
Results / Design Use this option to view the results of trajectory based calculation op-
tions. The results can be viewed in graphic format and in text format.
Results / Report Use this option to view the output file. Besides input data, this file
also contains the calculation results.

5.2 Construction Sequence

Click on the Construction Sequence node under Project Properties in the tree view on the left
of the screen. This will open the Project Properties – Construction Sequence window where
the relative timing of CPTs with respect to the installation of the piles and the excavation can
be specified.

With this option the user can specify if D-F OUNDATIONS has to take the effect of an excava-
tion and/or soil compaction due to pile driving into account. These two effects are reducing
respectively increasing the CPT values and are dependent on the time in the construction
process when the CPT is executed.

Figure 5.2: Construction Sequence window for the Tension Piles (EC7-NL) model

As default value the time order CPT – Excavation – Install is used as this is the most common
order in the construction process.

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5.3 Soil
In the tree view, the Soil node contains the sub-nodes Materials and Profiles, which should
be selected in order to enter or view the corresponding input data.

5.3.1 Materials
In the Soil – Materials window the materials and corresponding parameters for the project are
entered.

Figure 5.3: Soil – Materials window for Tension Piles (EC7-NL) model

Note: The table, at startup, is filled automatically with a list of materials obtained from Table
2.b of NEN 9997-1+C2:2017.

To make clear which materials are used in the profiles, use the Show Materials filter. To show
only the materials which are used in the profiles, select Used materials only. If All is selected,
all available materials are shown.

There are three ways to fill in the soil parameters:

⋄ section 5.3.1.1 Adding a ‘standard’ material (including its soil parameters) from Ta-
ble 2.b as defined in NEN 9997-1+C2:2017.
⋄ section 5.3.1.2 Adding manually a material and its required soil parameters.
⋄ section 5.3.1.3 Changing the properties of an existing material by matching them with
the properties of a ‘NEN material’ (i.e. from Table 2.b of NEN 9997-1+C2:2017).

5.3.1.1 Materials – Add from ‘Standard’

The Add from NEN 9997-1 button can be used to select a ‘standard’ material (including its
soil parameters) from Table 2.b as defined in NEN 9997-1+C2:2017.

⋄ To add a ‘standard’ material click the Add from NEN 9997-1 button to open the NEN 9997-1
Table 2.b window (Figure 5.4).

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Figure 5.4: NEN 9997-1 Table 2.b window for Tension Piles (EC7-NL) model

⋄ Select the required soil and then click OK to return to the Soil – Materials window where
the information for the selected soil will have been filled in.
⋄ To select and add more than one soil at the time, use the Shift or Control key when select-
ing.

Note: The NEN 9997-1 Table 2.b window displays either the high or the low values according
to the influence of the parameters. For example, for the Bearing Piles model the soil weight
has a negative influence so the high values must be chosen whereas for Tension Piles (EC7-
NL) and Shallow Foundations (EC7-NL) models, the soil weight has a beneficial effect on
the bearing/tension capacity so the low values much be chosen. The program will for each
calculation only use the materials as selected in the Materials window. It will never take
values from the standard tables directly. So the user must make sure the proper values have
been selected. For instance, when first performing a Bearing Piles (EC7-NL) calculation (with
’high’ values), the user should adapt the values before performing a Tension Piles (EC7-NL)
calculation by clicking the button in the Soil – Materials window.

Note: Only the parameter D50 (Median) (required for the soil types Gravel and Sand) must
always be provided by the user. D-F OUNDATIONS provides a default D50 , but if the soil is coarse
grained then the correct value will need to be input for correct calculation.

5.3.1.2 Materials – Add manually

The Insert row , Add row and Delete row buttons can be used to help build the
table of data. To enter or modify soil information manually, enter the following information in
the

Soil – Materials window:

Color The color of a material may be changed by clicking on it and selecting one
of the pre-defined basic colors from the window that opens, or a custom
color to be created by the user.
Soil name The name of the soil can be edited here.

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Soil type Select one of the available soil types from the drop-down list.
Peat is considered not to contribute to the maximum tension capacity of the
pile. In accordance with NEN 9997-1+C2:2017 Tabel 7.d the value for αt is
set to 0 by D-F OUNDATIONS.
Gamma- Enter the (characteristic) dry unit weight of the material (i.e. when the ma-
unsat terial is above the water level).
Gamma-sat Enter the (characteristic) saturated unit weight of the material (i.e. when the
material is below the water level).
Friction Enter the (characteristic) angle of internal friction (phi). The value must lie
angle between 0◦ and 90◦ .
D50 Enter the (characteristic) median grain size. This column only applies to
(median) the soil types Sand and Gravel. This parameter is used to determine the
reduction factor for αt according to NEN 9997-1+C2:2017 Table 7.c and
7.d:
⋄ For sand with D50 >0.6 mm, αt will be reduced by 25%.
⋄ For gravel with D50 > 2 mm, αt will be reduced by 50%.

Max. cone Choose the type of reduction of the cone resistance to be used when calcu-
resistance lating the shaft friction. Selecting Standard will cause the cone resistance
type to be reduced to either 12 MPa or 15 MPa, depending on the trajectory of
high qc values (as required by NEN 9997-1+C2:2017). Selecting Manual
will cause the input user defined value in the Maximum cone resistance
field to be used as the new maximum value.
Maximum Enter the manual value for the maximum cone resistance in this field. All
cone values in the CPT results larger than the maximum cone resistance will be
resistance set to this maximum for the calculation of the shaft friction only. This value
will only be used by D-F OUNDATIONS if Max. cone resistance type is set to
Manual.
Apply Mark the checkbox to allow tension capacity in the material, or unmark the
tension checkbox to define the material as having no tension capacity. The shaft
friction factor for materials without tension capacity is set to zero.
Minimal/ The minimum/maximum voids ratios are used to allow for soil compaction.
Maximal The values entered in these fields must lie between 0 and 1. For Dutch
Void Ratio conditions the values 0.8 (maximum void ratio) and 0.4 (minimum void ratio)
are recommended.

5.3.1.3 Materials – Match Material

Matching a material with Table 2.b of NEN 9997-1+C2:2017 does not depend on the selected
model, so refer to section 4.3.1.3 for Bearing Piles (EC7-NL) model.

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5.3.2 Profiles
Different actions are possible in the Soil / Profiles node of the tree view:

⋄ section 5.3.2.1 Adding a profile;

⋄ section 5.3.2.2 Modifying an existing profile;
⋄ section 5.3.2.3 Viewing and editing the layers representation of a profile;
⋄ section 5.3.2.4 Entering additional data;
⋄ section 5.3.2.5 Viewing the soil profile;
⋄ section 5.3.2.6 Viewing the pressures profile if available.

5.3.2.1 Adding Profiles

Adding a profile does not depend on the selected model, so refer to section 4.3.2.1 for Bearing
Piles (EC7-NL) model.

5.3.2.2 Options for existing profiles

Options for existing profiles are the same for all the models, so refer to section 4.3.2.2 for
Bearing Piles (EC7-NL) model.

5.3.2.3 Editing Layers

To view a graphic representation of a CPT, corresponding to its profile, select the correspond-
ing sub-node under the Soil / Profiles node in the tree view. The Layers tab of the Soil / Profiles
window opens. The red line in the graph corresponds to the qc value, and the blue line corre-
sponds to the friction. On the right side of the plotted CPT, a soil layer interpretation is drawn.
D-F OUNDATIONS automatically interprets all imported CPTs, based on the interpretation rule
that is selected by the user in the CPT Rule selection box below the graph. To use the pro-
posed soil layer interpretation, click the button to transport the interpretation into a profile
to be used in the project.

Note: If during the interpretation of a CPT, the point corresponding to the cone resistance and
the friction ratio of a layer is situated outside the limits of the diagram of the selected rule (i.e.
Figure 3.9 in section 3.2.2), the program will assign an Undetermined material to this layer with
unrealistic properties. That’s why the user must always review the automatic interpretation of
the CPT before performing a calculation. In such case, the user must select himself the
appropriate material from the drop-down list of available materials using its expertise.

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Figure 5.5: Soil – Profiles window, Layers tab

CPT Rule Select the interpretation rule used by D-F OUNDATIONS to automatically inter-
pret the imported CPT. Six different rules are available:
⋄ The NEN rule
⋄ The NEN stress dependent rule
⋄ The CUR rule
⋄ The 3-type rule
⋄ The Qc only rule
⋄ The User defined rule
The Qc only rule is especially useful for the interpretation of CPTs that do
not contain information about the friction.
Users may define their own interpretation rules by selecting the last option
in the list of rules: User defined rule. Before using a user defined rule, it
must have been specified in the CPT Interpretation Model window (sec-
tion 3.2.2).
Min. layer All interpretation rules make use of one additional parameter: the minimum
thickness layer thickness, specified in the Min. layer thickness input field below the
selection list. To prevent D-F OUNDATIONS from generating layers that are
too thin to be significant when modeling the problem, the minimum layer
thickness should be increased.
Coordinates As the CPT file does not always contain X and Y co-ordinates, those values
can be entered in the X and Y input fields in the Coordinates sub-window.

A profile is presented in two ways, both graphically and in a table. The data of the profile can
be entered or changed in two ways:

⋄ by editing data in the table

⋄ by graphically editing the picture in the middle of the window.

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Tabular input can be realized by editing the table on the right hand side of the input window.
Use the Insert row , Add row and Delete row buttons next to the table to add or
remove layers in the profile.

The table allows the following changes:

Top Level The top level of each soil layer can be edited manually.
Material Materials can be selected from the list of soil layers that were entered in the
Soil – Materials window.

Soil layers can be added to the profile by clicking the Add boundary button and clicking
anywhere in the graphic representation of the profile to add a layer below that level. Layer
boundaries can be changed dragging them upwards or downwards using the mouse. While
dragging, the level is indicated in a panel below the button bar and the table is updated con-
tinuously.

The Pore Pressure and OCR tab allows additional data to be input for each soil layer, as
described below the figure:

Figure 5.6: Soil – Profiles window for Tension Piles (EC7-NL) model, Pore Pressure and
OCR tab

Add Pore Pr. Enter the value of the pore pressure at the top of the layer which is addi-
top tional to the hydrostatic pore pressure caused by the distance below the
phreatic surface. Thus the total water pressure at a point is the sum of the
hydrostatic pressure and the additional pore pressure at that point. Addi-
tional pore pressures are assumed to vary linearly across each soil layer.
Add Pore Pr. Enter the value of the pore pressure at the bottom of the layer which is
bot additional to the hydrostatic pore pressure caused by the distance below
the phreatic surface. Thus the total water pressure at a point is the sum
of the hydrostatic pressure and the additional pore pressure at that point.
Additional pore pressures are assumed to vary linearly across each soil
layer.
OCR Enter the over-consolidation ratio for each layer.

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5.3.2.4 Additional Data

Figure 5.7: Soil – Profiles window, Additional Data tab

Under the Additional Data tab, the following information may be entered:

Phreatic This value specifies the dividing level between the dry soil (above the
level phreatic level) and the wet soil (below the phreatic level). The default value
used by D-F OUNDATIONS corresponds to the ground level of the imported
CPT file (GEF, CPT or SON) lowered by 0.5 m.
Pile tip level Although desirable, it usually turns out that the application of a single pile
tip level within a project is not realistic. Variations in the level of the bearing
layer found in the CPTs force the constructor to apply several pile tip levels.
The required pile tip level can be specified separately for each CPT. The
design option of D-F OUNDATIONS suppresses the various specified pile tip
levels in favor of the defined pile tip trajectory.
In that case each calculation step (read: each pile tip level) uses the trajec-
tory level as the pile tip level for all CPTs involved in the calculation.
Top of ten- The calculation of the tension capacity will start from this level. Note that
sion zone this level must be at least 1 m beneath the excavation level (or the surface
level if no excavation is required). D-F OUNDATIONS checks this requirement,
and if it is not met, D-F OUNDATIONS provides a warning and resets this level
to the required level.
Copy Click this button to display the Additional Data – Copy from Profiles window.
From. . . In this window select the name of one of the profiles and click OK to copy
the additional data given for that profile into the fields for this profile.
Copy To. . . Click this button to display the Additional Data – Copy to Profiles window. In
this window select the names of any profiles which should have the same
additional data as defined for the current profile. Click OK to copy this data
to the selected profiles.

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5.3.2.5 Viewing Profiles

A graphic representation of the profiles defined for a project can be viewed by clicking one of
the two right most tabs in the Soil – Profiles window:

⋄ The Additional Data tab (Figure 5.8) displays the CPT and, if available, the profile with
data such as defined layers, material types per layer and user defined levels (phreatic
level, tension zone level etc.). The standard qc diagram (red line in Figure 5.8) is also
displayed.
⋄ The Summary Pressures tab (Figure 5.9) also displays the CPT

Figure 5.8: Soil – Profiles window, Additional Data tab

Use the buttons in the button bar to manipulate the view.

Note: By right-clicking the mouse button in the CPT/Profile view of the Additional Data tab
and selecting View Preferences, the Project Properties window opens to determine which
names for the soil materials will be used in the profile view.

5.3.2.6 Summary Pressures

If they are available, the Summary Pressures tab (Figure 5.9) also displays the soil pressures
as derived from the data set in the Soil – Profiles window.

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Figure 5.9: Soil – Profiles window, Summary Pressures tab

Use the buttons in the button bar to manipulate the view.

Note: Those pressures are always displayed for the original profile, and excavations and
surcharges are not taken into account in this display.

5.4 Foundation
In the tree view, the Foundation node contains the following sub-nodes:

⋄ Pile Types
⋄ Pile Properties
⋄ Top View Foundation

Browsing through these nodes, allows data applying to the foundation to be viewed and en-
tered. The available options are described below.

5.4.1 Pile Types

In the Foundation – Pile Types window (reached by clicking on the Pile Types node) types of
piles can be added and their characteristics defined.

D-F OUNDATIONS is supplied with a database of pre-defined pile shapes. When one of the
pre-defined shapes is selected, a drop down list of pre-defined pile types (depending on the
selected shape) becomes available in the Pile type field. If one of the pre-defined types is
selected, the corresponding pile type data are filled in automatically and cannot be edited.
Select the pile type User defined to enter all data manually.

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Figure 5.10: Foundation – Pile Types window for Tension Piles (EC7-NL) model

The required pile shape can be selected by clicking on the pertinent diagrammatic represen-
tation of the geometry in the panel on the left of the window (Figure 5.10). In the Dimensions
sub-window at the top, the pile dimensions can be entered. The geometric parameters that
are required depend on shape chosen:

Rectangular pile Enter the base width and base length of the pile.
(for piles)

Rectangular pile Enter the width, length and height of the base, as well as
with enlarged base the width and length of the shaft.

Rectangular pile Enter the circumference and cross-section of the pile.

(for sheet piling)

Round pile Only the diameter is required.

Round tapered pile Enter the diameter at the pile tip and the increase in di-
ameter per m pile length.

Round hollow Enter the external diameter and the wall thickness of the
pile with closed pile.
base

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Round hollow Enter the external diameter and the wall thickness of the
pile with open base pile.

Round pile with Enter the pile and base diameters and the height of the
enlarged base base.

Round pile with Enter the pile and base diameters. The height of the
lost tip base is automatically set to zero.

Round pile with Enter the pile and base diameters and the height of the
in situ formed base.
expanded base

H-shaped profile Enter the height and width of the H-shape, as well as the
thickness of the web and of the flange.

Note: These dimensions are indicated on the diagrams on the Pile shape sub-window.

When the pile shape is selected, the following information can be entered:

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Pile type Use this sub-window to enter information about the pile type.
αt is the pile factor for the shaft friction. The value for the factor, according
to NEN 9997-1+C2:2017, depends on the soil material:

⋄ For soil types sand, gravel and loam the value for αt depends on the
pile type. Therefore it can be specified by selecting one of the standard
pile types from the combo box. As a result the actual value for αt will
be displayed in the current value box. If selecting a user defined pile
type for αt , valid for sand, gravel and loam layers, either a vibrating or
a low vibrating pile type can be selected. This enables the user to steer
the influence of the pile type on the reduction of qc (due to excavation
and over-consolidation). Choosing one of the user defined types will
always have the consequence that the value entered for αt , valid for
sand and gravel layers, will NOT be adjusted for any instance of coarse
grain (NEN 9997-1+C2:2017 art. 7.6.2.3(i)).

⋄ For the soil type clay the factor according to the standard is depth-
dependent and thus has no single value. As a result the current value
box displays ‘N.A.’ (Not applicable) as the value can not be shown. If
"User defined" is selected as the subtype, only the parameter value is
entered. That value can and will be displayed as current value. For αt ,
valid for clay layers, only one user defined type can be selected. As pre-
scribed by NEN 9997-1+C2:2017, the value for αt must be reduced by
50% if the soil profile holds layers other than clay or peat.

⋄ The actual value of αt for peat is 0.

NOTE: The value given by the user will also be reduced by 50 % in cases
where the profile holds layers other than clay or peat.
Material Select the material from which the pile is made. The corresponding pile
weight is provided automatically and cannot be edited. If the material User
defined is selected then the unit weight of the pile material needs also to
be entered. The total weight of the pile is calculated automatically, based
on the pile dimensions and the material weight.
Unit weight Enter the unit weight of the pile material, if the pile Material has been se-
pile material lected as User defined. If this value is set to zero, D-F OUNDATIONS assumes
that the uplift of the pile due to the groundwater is also zero. In this case
the weight of the pile is not taken into account when calculating the bearing
capacity.
Material & In the Material field select the material of the user defined pile. The cor-
Young’s responding elasticity modulus is provided automatically for concrete, steel
modulus and timber and cannot be edited. If the material "User defined" is selected
then the Young’s modulus must also be entered.
Unit weight Enter the unit weight of the filling material, it is only available if the pile
filling shape has been selected as Round hollow pile with closed base and the
material pile factor αt for sand and gravel has been selected as Closed-ended steel
pipe pile. In this case the weight of the filling material is added to the weight
of the weight pile.

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Building a pile type database

Pile type definitions created in the Foundation – Pile Types window can be saved to a FOP file
by means of the Export option, reached by right clicking the Pile Types node in the tree view
and selecting Export from the context menu, or left clicking on the Pile Types node and then
selecting Export in the Action sub-window of the Foundation – Pile Types window. This allows
a database of pile types to be built up which can be used in future projects, allowing the pile
type definition with less effort and less chance of errors. Use the Import option in the same
context menu to select a previously saved FOP file for the pile type currently selected. When
the appropriate file has been located and opened, the pile types in the FOP-file are added as
new nodes under the Pile Types node.

5.4.2 Pile Properties

Use the Foundation – Pile Properties window to define the positions of the piles and the loads
for the project. There are several ways to do this, as described hereafter.

Figure 5.11: Foundation – Pile Properties window for Tension Piles (EC7-NL) model

In this window the following information can be entered:

Name In this box the pile position names are displayed. Each position automati-
cally receives a number when added to the list. The name can be changed
if desired.
X Enter the X coordinate of the position of the center of the pile. The same
coordinate system must be used as when entering the CPT coordinates.
Y Enter the Y coordinate of the position of the center of the pile. The same
coordinate system must be used as when entering the CPT coordinates.
Pile head The pile head level is used to specify for each pile the level of the pile head
level with regard to the reference level (usually NAP). This allows calculation with
deepened pile heads. If the pile head level is not entered the default level
(0.00 m NAP) applies.
Use Selecting Yes allows alternating loads to be accounted for by calculating
Alternating an extra safety factor γm;var;qc , according to NEN 9997-1+C2:2017 art.
Loads 7.6.3.3(c).

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Maximum/ The maximum tension load on the pile should be higher than the minimum
minimum tension load, which may receive a negative (=compressive) value. Char-
load on pile acteristic values of these loads should be specified. In practice, only the
ratio between the minimum and maximum value of the loads is important.
So, piles with minimum 100 kN and maximum 200 kN have the same safety
factor γm;var;qc as piles with minimum 10 kN and maximum 20 kN. Piles
with minimum values that equal the maximum values have no extra safety
factor (= 1.0). This safety factor never exceeds 1.5.
Limit state The load on the piles (Fs;d ) can be specified for both STR/GEO and ser-
STR/GEO viceability limit states. The values for Fs;d (STR/GEO) and Fs;d (service-
ability) are derived by multiplying the characteristic loads of the building on
Serviceability the pile foundation with the corresponding load factors which need deter-
limit state mined according to NEN 9997-1+C2:2017 appendix A. Usually the calcu-
lation values to be entered here are determined by the constructor of the
building. For more information on limit state STR/GEO and serviceability,
see NEN 9997-1+C2:2017 art. 2.4.7 & 2.4.8.

Use the toolbar on the left side of this window to edit the table:

Use this button to insert a row in the table.

Use this button to add a row to the table.

Use this button to delete a row from the table.

Use this button to generate a grid of piles with the same properties (see below).

Use this button to change the properties (Pile head level, Surcharge, Design val-
ues of load on pile) of all the pile positions (see below).

Use this button to cut a selected part of the table.

Use this button to copy a selected part of the table.

Use this button to paste a selected part in the table.

Click the fourth button in Pile Properties window to open a window where a grid of pile
positions can be specified.

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Figure 5.12: Pile Grid window for Tension Piles (EC7-NL) model

The pile properties can also be entered in the Pile Grid window. This results in the same
properties for all pile positions in the grid, but, if required, these properties can later be edited
individually.

In this window the following information can be entered:

Start at Enter the start coordinates for the center of the bottom-left pile in the grid.
The same coordinate system must be used as when entering the CPT co-
ordinates. To help with setting the positions of the piles relative to the used
profiles/CPT’s, the option Set relative to profile can be used to select a
profile of which the coordinates will be used as base for the pile plan.
Centre Enter the distance between the centers of adjacent piles.
to centre
distance
Number of Enter the number of piles in each direction.
piles
Parameters For more information see the Pile Properties (tension piles) window above.
Use pile grid Enable this check box to replace the existing pile positions in the project
to replace with those defined by the grid. If this check box is left empty, the positions
current pile in the pile grid will be added to the existing pile positions.
positions

Click the fifth button in Pile Properties window to open the Edit properties for all positions
window (Figure 5.13) in which the Pile head level and Maximum/Minimum tension loads on
the pile of all pile positions can be edited and/or modified. If modified, the properties of all
pile positions will automatically be updated in the corresponding column of the Pile Properties
window (Figure 5.11).

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Figure 5.13: Edit properties for all positions window for Tension Piles (EC7-NL) model

5.4.3 Top View Foundation

Select Top View Foundation under the Foundation node in the tree view to display this window.
Here the pile locations and types and the CPTs can be seen in plan view.

Figure 5.14: Foundation – Top View Foundation window for Tension Piles (EC7-NL)
model

The button bar of this window allows the view to be manipulated in various ways:

Click this button to select objects using the cursor and to finish using any of the
other modes described below.

Click this cursor to activate the pan mode. Click and drag the view to see a
different part of it.

Click this button to activate the zoom-in cursor. Then click on the part which is to
become the centre of the desired enlarged view. Repeat this step several times if
necessary.

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Click this button to undo the last zoom-in step. If necessary, click several times to
retrace each consecutive zoom-in step that was made.

Click this button to select a rectangle for enlargement. The selected part will be
enlarged to fit the window. Repeat this step several times if necessary.

Click this button to measure the distance between two points. Click on one point
and the distance from there to the current mouse position is displayed in the panel
at the bottom of the view.

Click this button to undo the last zoom step.

Click this button to restore the original dimensions of the view.

5.5 Excavation
Click the Excavation node in the tree view to display this window. Here, one Excavation level
can be entered for all soil profiles. Under Reduction of cone resistance select the method by
which the cone resistance is to be reduced, in order to take the effect of the excavation into
account.

Figure 5.15: Excavation window

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Manual reduction of cone resistance

The reduction percentages per layer per CPT can be specified by the user by selecting Man-
ual, selecting the relevant CPT, and then entering the reduction percentages Qc Reduction
for the Top Level of each soil layer. For the selected CPT the reduction will take place via:

(100 − red%)
qc;red = qc × (5.1)
100

Safe (NEN) reduction of cone resistance

If Safe (NEN) is selected under Reduction of cone resistance, all CPTs are reduced in a very
safe manner in accordance with NEN 9997-1+C2:2017 art. 7.6.2.3(k) and selection of qc is
restricted to NEN 9997-1+C2:2017 art 7.6.2.3(i). This implies complete relaxation of the soil
beneath the excavation as well as an infinite width of the excavation.

Begemann reduction of cone resistance

This method also reduces all CPTs at once. It takes into account the proximity of the edge of
the excavation to the construction. The distance to this edge can be varied in the Distance
edge pile to excavation boundary field. Note that this distance is the distance between the
excavation edge and the pile(s) on the outside of the pile plan. To see the excavation, click
Top View Foundation in the tree view to display the pile plan.

The effect of the excavation (reduction of the cone resistance) can be viewed per CPT in the
drawing on the left of the Excavation window. The drawing also displays the effect in terms of
stresses. The initial effective stress shows the stress without excavation. The effective stress
shows the stress after excavation.

5.6 Calculations
To start a calculation, click the Calculation node in the tree view or select Start in the Cal-
culation menu. A window opens with various options to be set and the types of calculation
available. The top half of the window relates to data and options required for tension pile
calculations (described in section 5.6.1), whilst the bottom part of the window is related to the
selection of the type of calculation to be performed (described in section 5.6.2).

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Figure 5.16: Calculation window for Tension Piles (EC7-NL) model

5.6.1 Options for a Tension Piles calculation

Before calculating the project design, a number of options, which will apply to all tension piles,
need to be specified.

Note: Some of the options are found in the sub-window Overrule parameters. This allows
certain parameters to be overruled which otherwise would be determined according to the
standard. The user must make sure that an overruling of parameters is allowable. These
parameters must be used with the utmost caution.

Figure 5.17: Calculation window for Tension Piles (EC7-NL) model

In the upper half of the Calculation window the following information can be entered:

Unit weight Enter the unit weight of water. The default value is set to 9.81 kN/m3 .
water
Surcharge Enter the (permanent) surcharge placed at ground level / excavation level.

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Rigidity of Indicate the rigidity of the superstructure as either Non-rigid or Rigid ac-
superstructure cording to NEN 9997-1+C2:2017 art. 7.6.1.1(c).
A restriction for the schematics is that for each calculation only (parts of)
buildings that can be regarded as either completely “rigid” or completely
“non-rigid” can be included in one calculation. If a building is regarded as
partly “rigid” and partly “non-rigid” (for instance a building with a rigid core)
at least two calculations must be carried out: one for the rigid part and one
for the non-rigid part. Also if a building consists of several different parts
that can be regarded as rigid, a calculation must be made for each part.
The reason for this restriction is that a proper value for the ξ3 and ξ4 fac-
tor (used to calculate the pile tension capacity) cannot be determined for
‘mixed rigidity’ schematics.
Maximum The values given in NEN 6740:1991 are provided as the default settlement
allowed demand for which verification takes place. The values of NEN 6740:1991
settlement are used because the standard NEN 9997-1+C2:2017 does not specify the
maximum values for allowed settlement. It is possible to edit these values
for either of the two limit states. In case of limit state EQU/GEO, the default
is an advised value whereas for serviceability limit state the default should
be considered a minimum value. If the values do not match the defaults this
will be explicitly mentioned in the report.
Maximum The values given in NEN 9997-1+C2:2017 are provided as the default rel-
allowed ative rotation demand for which verification takes place. It is possible to
relative edit these values for either of the two limit states. In case of limit state
rotation EQU/GEO, the default is an advised value whereas for serviceability limit
state the default should be considered a minimum value. If the values do
not match the defaults this will be explicitly mentioned in the report.
ξ3 Here the value for ξ3 (the correlation factor for average value of calculated
pile resistances) can be overruled. This factor depends on the rigidity of
the superstructure and number of CPTs (see Tables A.10a and A.10b in
NEN 9997-1+C2:2017).
ξ4 Here the value for ξ4 (the correlation factor for the minimum value of calcu-
lated pile resistances) can be overruled. This factor depends on the rigidity
of the superstructure and number of CPTs (see Tables A.10a and A.10b in
NEN 9997-1+C2:2017).
γm;var;qc Here the user can enter its own value for γm;var;qc . This factor usually re-
sults from the maximum and minimum alternating loads, as given in the Pile
Properties window (section 5.4.2) and calculated according to NEN 9997-
1+C2:2017 art. 7.6.3.3(d). The default overruling value is 1.
NOTE: If overruled, this factor will have an effect only if alternating loads
are used, i.e. only if the option Use Alternating Loads in the Pile Properties
window (section 5.4.2) is selected.
γst Here the users can define their own value for γs;t the safety factor for ma-
terials. Normally this would be derived from Tables A.6-A.8, and A.16 in
NEN 9997-1+C2:2017. The default overruling value is 1.
γγ Here the users can define their own value for γγ , the safety factor for the
total soil weight. Normally this would be derived from Tables A.2-A.3 and
A.4a-A.4b in NEN 9997-1+C2:2017. The default overruling value is 1.

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Eea;gem The value for the average soil modulus can be overruled. This modulus
would normally be calculated the same way as the average soil modulus
for model Bearing Piles (EC7-NL) according to NEN 9997-1+C2:2017, art.
7.6.4.2(k) (section 16.5). However, in this case the modulus is calculated at
pile tip level, instead of at the level of 4D beneath the pile tip. In addition,
the value found this way is corrected for Tension Piles by multiplying this
calculated modulus by 4.
Use Enable this checkbox to take compaction of soil due to installation of dis-
compaction placement piles into account. The positive effect on the qc value should be
checked by performing CPTs after installation (see NEN 9997-1+C2:2017
art. 7.6.2.3(k)). Compaction is not used for non-displacement piles types,
such as bored and auger piles.
Overrule Enable this checkbox to prevent the excavation from being taken into ac-
excavation count.
Overrule ex- Enable this checkbox to prevent the excess pore pressures (that were spec-
cess pore ified with the Soil - Profiles (EC7-NL) option) from being taken into account.
pressure

5.6.2 Preliminary Design Tension Piles

D-F OUNDATIONS can perform a preliminary design for tension piles according to the NEN 9997-
1+C2:2017. Three different types of preliminary design calculation are available:

⋄ Indication bearing capacity outlined in section 5.6.2.1;

⋄ Bearing capacity at fixed pile tip levels outlined in section 5.6.2.2;
⋄ Pile tip levels and net bearing capacity outlined in section 5.6.2.3.

First of all the type of calculation needs to be selected. Some types require additional data.
Secondly the CPTs and pile types, to be included in the preliminary calculations, need to be
selected. Note that the order in which the items are selected determines the order of the
calculations.

Figure 5.18: Calculation window, Preliminary Design for Tension Piles (EC7-NL) model

Once all of the options and requisite information have been inputted, click Start to start the
calculation.

Note: When a calculation is started, any previous calculation results will be replaced. To
retain previous results, print the results or make a copy of the project files. Alternatively, set

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the default action to Always Save As instead of Always Save for the Save on Calculation option
on the General tab in the Program Options window (Tools menu). In that case a ‘Save As’
dialog will automatically appear each time a calculation is started.

Note: The nature of the calculation which has to be performed greatly influences the time
needed to perform the calculation. The number of piles and the number of selected CPTs
and pile types have an influence on the required calculation time: if a large number of piles is
placed in a irregular geometry the calculation time may increase considerably.

5.6.2.1 Preliminary design: Indication bearing capacity

This option is used to obtain an indication of the bearing capacity in relation to a range of pile
tip level(s).

Instead of the specified pile tip levels given per CPT, a pile tip trajectory is used. This tra-
jectory is determined by means of a top and bottom limit in m above or below the reference
level (usually NAP). The interval of the trajectory determines the number of calculations to be
performed, with a maximum of 151.

When defining a trajectory, the specified skin friction zone and pile tip levels do not need to
be taken into account. Both the top and bottom limits of the trajectory must meet a number of
requirements. The top limit value (Begin) must at least as low as the lowest pile head level and
the lowest Top of tension zone (as specified in the Additional Data tab of the Soil – Profiles
window in section 5.3.2.3). The Top of tension zone itself must be at least 1 m deeper than
the lowest ground level and lowest excavation level. The bottom limit value (End) must be at
least as high as the shallowest CPT. The Interval must be chosen so that no more than 151
calculations will be performed.

The results for each trajectory level are presented in a table as well as a graph. Both the
table and graph can be viewed with the Design sub-node in the Results node. Depending
on the geometry, for each single pile, or group of piles with equal parameters (pile type, pile
dimensions, distance to excavation, loading and geometry), the design value of the capacity
in tension (Fr;tension;d ), pull out force (Max. mobilized soil weight) and the effective weight of
the pile as function of the pile tip level is given. For more information about viewing results,
refer to chapter 7.

Note: The effective weight of the pile is included in Rt;d as well in the pull out force.

5.6.2.2 Preliminary design: Bearing capacity at fixed pile tip levels

This option is used to obtain an indication of the bearing capacity in relation to the pile tip level
of each CPT.

The results of this calculation are the design value of the capacity in tension (Rt;d ), pull out
force (Max. mobilized soil weight) and the effective weight of the pile for each CPT at its
fixed pile tip level. These results are displayed in a table that can be viewed using the Design
sub-node in the Results node. For more information about viewing results, refer to chapter 7.

Note: The effective weight of the pile is included in Fr;tension;d as well in the pull out force.

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5.6.2.3 Preliminary design: Pile tip levels and net bearing capacity
This option is used to obtain an indication of the required pile tip level per CPT in order to
realize the desired net bearing capacity (Fs;net;d ). This desired net bearing capacity can be
regarded as the required tension force for failure of the pile.

Using this option, the program will determine, for each CPT entered, the highest pile tip level
within the boundaries set for which the design value of the capacity of the pile is greater than
or equal to the “net bearing capacity” value. The required pile tip level per CPT is located in a
user-defined pile tip trajectory.

This trajectory is specified by means of a top (Begin) and bottom (End) limit in m above/below
reference level. The Interval of the trajectory determines the number of calculations to be
performed, up to a maximum of 151. Information about the requirements that must be met
when defining the trajectory can be found in section 5.6.2.1.

The trajectory may consist of at most 151 intervals. Together with the trajectory definition the
required Net bearing capacity (Fs;net;d ) must be entered. This value is used as a stopping
criterion for the calculation. As soon as a level has been detected for a CPT where the cal-
culated tension force equals or exceeds the required net tension capacity, the calculation for
that CPT is stopped after which the calculated capacities are displayed. For more information
about viewing results, refer to chapter 7.

Note: If within the trajectory no level is found for a CPT with the required net bearing capacity,
this is marked as ’******’ in the Pile Tip Level column. In order to provide some idea, the
calculated capacities for the last trajectory level are included.

Note: After the calculation in D-F OUNDATIONS the outputs Rt;d;avg and Rt;d;min are displayed.
These values are calculated as follows:

(Rs;cal ) avg 1
Rt;d;avg = × (5.2)
ξ3 γs;t

(Rs;cal ) min 1
Rt;d;min = × (5.3)
ξ4 γs;t

5.6.3 Verification Tension Piles

This calculation option performs a complete verification according to NEN 9997-1+C2:2017
standard. All required calculations (bearing capacity and settlement) are carried out according
to these standards. The CPTs and pile type to be used in the calculation should also be
selected here. Contrary to the preliminary design options the calculations are complete and
include settlements and rotations. The complete pile plan is also considered, taking care of
group effects. Note that only one pile type can be used per verification. The CPT test level
is used to perform a separate calculation of the bearing capacities of all CPTs at that level.
These bearing capacities are then used to check the compliance with the demands as set by
NEN 9997-1+C2:2017 art. 3.2.3(e) regarding the number of CPTs and their spacing.

For a complete verification, the user can specify a different pile tip level for each CPT. Finally,
this increases the chance that the required standard will be met.

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Figure 5.19: Calculation window, Verification for Bearing Piles (EC7-NL) model

The results are presented in the report which can be accessed by clicking the Report sub-
node in the Results node. For more information about viewing results, refer to chapter 7.

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 6 Shallow Foundations (EC7-NL) – Input & Calculations
Just as with the other models, two types of data are required for the shallow foundations
model:

⋄ Firstly, data is required to determine the soil characteristics (soil profiles, including the
ground water level, placement depth of foundation, and so on). Although helpful, CPTs
are not required for shallow foundations. The soil data is entered in the windows that
appear when selecting the sub-nodes below the Soil node in the tree view.
⋄ Secondly, data is required to specify the construction (of the foundation), for example
dimensions, foundation plan, and so on. The relevant options can be found in the
windows that appear when selecting the sub-nodes below the Foundation node in the
tree view.

Before calculating the project design, a number of options that will apply to all shallow founda-
tions need to be specified in the window that appears when the Calculation node is selected
in the tree view.

6.1 Tree view

Figure 6.1: Main window for the Shallow Foundations (EC7-NL) model

For the shallow foundations model, the tree view contains the following nodes and sub-nodes:

Project Use this option to describe and identify the project.

Properties /
Description
Soil / Use this option to enter the soil material properties.
Materials
Soil / Use this option to enter and view a soil profile, as well as to enter additional
Profiles data related to the profile. Optionally, CPTs can be used here as base for
the profiles.
Soil / Slopes Use this option to input slope geometries, if required. Elsewhere in
D-F OUNDATIONS the slopes can be linked to foundation elements.

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Foundation / Use this option to enter the dimensions of the project’s foundation elements.
Types Round, rectangular or strip-shaped elements can be analyzed.
Foundation / Use this option to enter the loads together with their initial eccentricities,
Loads both for limit state STR/GEO and serviceability limit state. For horizontal
loads the angle (in the horizontal plane) between the load and the longitu-
dinal axis of the foundation element can also be specified.
Foundation / Use this option to define the foundation plan. For each position the corre-
Foundation sponding element type and the angle (in the horizontal plane) at which the
Plan element must be placed can be entered. A load, soil profile and slope (if
any) can also be linked to each element.
Foundation / Use this option to display a graphic representation of the layout of the en-
Top View tered foundation element(s) and profiles.
Foundation
Calculation Use this option to specify the calculation settings and verification require-
ments, and to execute the calculation.
Results / Use this option to view the intermediate results file, if there is one. Whether
Intermediate or not calculation results are written to this file is determined by enabling
the Write intermediate results checkbox in the Calculation window.
Results / Use this option to view the output file. This file contains the calculation
Report results and the input data.

6.2 Soil
In the tree view, the Soil node contains the sub-nodes Materials, Profiles and Slopes, which
should be selected to enter or view the corresponding input data.

6.2.1 Materials
In the Soil – Materials window the materials and corresponding parameters for the project can
be entered.

Figure 6.2: Soil – Materials window for Shallow Foundations (EC7-NL) model

To make clear which materials are used in the profiles, use the Show Materials filter. To show
only the materials which are used in the profiles, select Used materials only. If All is selected,
all available materials are shown.

There are three ways to fill in the soil parameters:

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⋄ section 6.2.1.1 Adding a ‘standard’ material (including its soil parameters) from Ta-
ble 2.b as defined in NEN 9997-1+C2:2017.
⋄ section 6.2.1.2 Adding manually a material and its required soil parameters.
⋄ section 6.2.1.3 Changing the properties of an existing material by matching them with
the properties of a ‘NEN material’ (i.e. from Table 2.b of NEN 9997-1+C2:2017).

6.2.1.1 Materials – Add from ‘Standard’

The Add from NEN 9997-1 button can be used to select a ‘standard’ material (including its
soil parameters) from Table 2.b as defined in NEN 9997-1+C2:2017.

⋄ To add a ‘standard’ material click the Add from NEN 9997-1 button to open the NEN 9997-1
Table 2.b window (Figure 6.3).

Figure 6.3: NEN 9997-1 Table 2.b window for Shallow Foundations (EC7-NL) model

⋄ Select the required soil and then click OK to return to the Soil – Materials window, where
the information for the selected soil will have been filled in.
⋄ To select and add more than one soil at the time, use the Shift or Control key when select-
ing.

Note: The NEN 9997-1 Table 2.b window displays either the high or the low values according
to the influence of the parameters. For example, for the Bearing Piles model the soil weight
has a negative influence so the high values must be chosen whereas for Tension Piles (EC7-
NL) and Shallow Foundations (EC7-NL) models, the soil weight has a beneficial effect on
the bearing/tension capacity so the low values much be chosen. The program will for each
calculation only use the materials as selected in the Materials window. It will never take
values from the standard tables directly. So the user must make sure the proper values have
been selected. For instance, when first performing a Bearing Piles (EC7-NL) calculation (with
’high’ values), the user should adapt the values before performing a Tension Piles (EC7-NL)
calculation by clicking the button in the Soil - Materials window.

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6.2.1.2 Materials – Add manually

The Insert row , Add row and Delete row buttons can be used to help build the table
of data. To enter or modify soil information manually, enter the following information in the
Soil – Materials window:

Color Clicking on the color of a material opens the Color window where one of
the pre-defined basic colors, or a custom color created by the user, can be
selected.
Soil Name The name of the soil can be edited here.
Soil type Select the soil type from the drop-down list.
Gamma- Enter the (characteristic) dry unit weight of the material (i.e. for soil above
unsat the water level).
Gamma-sat Enter the (characteristic) saturated unit weight of the material (i.e. for soil
below the water level).
Friction Enter the (characteristic) angle of internal friction φ. It must lie between 0
angle (phi) and 90 degrees.
Cohesion (c) Enter the (characteristic) effective cohesion c.
Cu Enter the (characteristic) undrained shear strength su .
(F_undrained)
Cc Enter the (characteristic) primary compression index Cc .
Ca Enter the (characteristic) secondary compression index Cα .
Initial void Enter the (characteristic) initial void ratio e0 . Note that this parameter does
ratio (e0) not appear in the NEN 9997-1+C2:2017 Table 2.b as this is not a part of it.
However, after selecting a material from the table a default value for this
parameter is automatically calculated, using:
⋄ For peat:
e0 = 15.5 when γsat = 10 kN/m3
⋄ ⋄ ⋄

e0 = 4.9 when γsat = 12 kN/m3

e0 = 2.9 when γsat = 13 kN/m3
⋄ For all other soil types: e0 = (γs − γsat ) / (γsat − 10) where γsat is the
saturated unit weight and γs is the unit weight of the grains (26.5 kN/m3 ).

6.2.1.3 Materials – Match Material

Matching a material with Table 2.b of NEN 9997-1+C2:2017 does not depend on the selected
model, so refer to section 4.3.1.3 for Bearing Piles (EC7-NL) model.

6.2.2 Profiles
Different actions are possible in the Soil / Profiles node of the tree view:

⋄ section 6.2.2.1 Adding a profile;

⋄ section 6.2.2.2 Modifying an existing profile;
⋄ section 6.2.2.3 Viewing and editing the layers representation of a profile;
⋄ section 6.2.2.4 Entering additional data;
⋄ section 6.2.2.5 Viewing the soil profile;
⋄ section 6.2.2.6 Viewing the pressures profile if available.

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6.2.2.1 Adding Profiles

Adding a profile does not depend on the selected model, so refer to section 4.3.2.1 for Bearing
Piles (EC7-NL) model.

6.2.2.2 Options for existing profiles

Options for existing profiles are the same for all the models, so refer to section 4.3.2.2 for
Bearing Piles (EC7-NL) model.

6.2.2.3 Editing Layers

Viewing a graphic representation of a CPT, corresponding to its profile, is similar to the Bearing
Piles (EC7-NL) model, so refer to section 4.3.2.3.

6.2.2.4 Additional Data

Figure 6.4: Soil – Profiles window, Additional Data tab for Shallow Foundations (EC7-NL)
model

Under the Additional Data tab, the following information can be entered:

Phreatic level This value specifies the dividing level between the dry soil (above the
phreatic level) and the wet soil (below the phreatic level). The default
value used by D-F OUNDATIONS corresponds to the ground level of the
imported CPT file (GEF, CPT or SON) lowered by 0.5 m.
Placement depth This is the level at which the bottom of the foundation element is
of foundation placed, i.e. the foundation level.
element
Concentration The concentration factor mσ influences the calculation of the set-
value according tlement. This calculation (according to NEN 9997-1+C2:2017, arti-
to Frolich cle 6.6.2(d)) normally follows the model described by Boussinesq (in
which case the concentration value equals 3), but by raising the con-
centration value to 4, a4, a stiffness increasing with depth can be
emulated.
Copy From. . . Click this button to display the Additional Data – Copy from Profiles
window. In this window select the name of one of the profiles and
click OK to copy the additional data given for that profile into the
fields for this profile.
Copy To. . . Click this button to display the Additional Data – Copy to Profiles
window. In this window select the names of any profiles which should
have the same additional data as defined for the current profile. Click
OK to copy this data to the selected profiles.

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6.2.2.5 Viewing Profiles

A graphic representation of the profiles defined for a project can be viewed by clicking one of
the two right most tabs in the Soil – Profiles window:

⋄ The Additional Data tab (Figure 6.5) displays the CPT and, if available, the profile with
data such as defined layers, material types per layer and the phreatic level. The stan-
dard qc diagram (red line in Figure 6.5) is also displayed.
⋄ The Summary Pressures tab (Figure 6.6) also displays the CPT.

Figure 6.5: Soil – Profiles window, Additional Data tab

Use the buttons in the button bar to manipulate the view.

Note: By right-clicking the mouse button in the CPT/Profile view of the Additional Data tab
and selecting View Preferences, the Project Properties window opens to determine which
names for the soil materials will be used in the profile view.

6.2.2.6 Summary Pressures

If they are available, the Summary Pressures tab (Figure 6.6) also displays the soil pressures
as derived from the data set in the Soil – Profiles window.

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Figure 6.6: Soil – Profiles window, Summary Pressures tab

Use the buttons in the button bar to manipulate the view.

Note: Those pressures are always displayed for the original profile, and loads are not taken
into account in this view.

6.2.3 Slopes
In this window the geometry of the slopes used in the project can be defined:

Figure 6.7: Soil – Slopes window

For each slope, enter the following information:

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Berm width Enter the distance between the edge of the foundation element and the top
of the slope.
Slope length Enter the horizontal measured distance between the slope top and the
slope bottom.
Slope height Enter the difference in height between the slope top and the slope bottom.

The meaning of these parameters is illustrated in the picture to the right of the table.

6.3 Foundation
In the tree view, the Foundation node contains the following sub-nodes:

⋄ Types of Shallow Foundations

⋄ Loads
⋄ Foundation plan
⋄ Top View Foundation

Browsing through these nodes, allows data applying to the foundation to be viewed and input.
The available options are described below.

6.3.1 Types of Shallow Foundations

In this window, the types of shallow foundations used in the project can be defined. Open the
window by selecting the Types sub-node in the tree view and then either selecting New to
create a new foundation type, or clicking on one of the names in the Types box to view and
edit a previously defined type.

Figure 6.8: Foundation – Types window for Shallow Foundations (EC7-NL) model

Select the required foundation shape and then enter the requisite information:

Round Specify the Diameter.

Rectangular Specify the Width and the Length.
Strip Specify the Width of the strip.

The dimensions are indicated in the diagrams on the right hand side of the window.

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For Type the choice between Prefab and Cast in place influences the horizontal bearing ca-
pacity of the foundation. Cast in place delivers a higher horizontal capacity as its contact
surface with the soil is assumed to be rougher.

Strip footings assume an indefinite length (whereas rectangular or round footings assume that
all dimensions are known). Because the L is infinite, Aef is in principal also infinite. However,
when determining factors like ic (undrained), iq and iγ (drained), Aef is to be determined
using Lef = 1 when appropriate (for Kappa = 90 degrees). Not appropriate is the case for
ic , iq and iγ where the horizontal load is runs parallel to the length axis of the foundation
(Kappa = 0). In that case, Aef is still to be considered infinite. In that case ic , iq and iγ are set
to 1. For all angles between 0 and 90 degrees linear interpolation between the values found
at 0 and 90 degrees will provide the correct answer. Note that this for the determination of ic
differs from the actual NEN 9997-1+C2:2017 article as that does not allow for the influence of
the angle. So this article was extended in D-F OUNDATIONS to include the angle.

6.3.2 Loads
Use this window to enter the vertical and horizontal load components applied to the founda-
tion. A distinction is made between the loads for limit states STR/GEO and serviceability limit
state:

Figure 6.9: Foundation – Loads window

Click on Loads in the tree view and then either select New to define a new load, or click on a
name in the Loads sub-window to view and edit a previously defined load.

In the Foundation – Loads window the following information can be entered:

Initial eccentricity Enter the eccentricity of the vertical load (Fs;v;d ) along the latitudinal
along latitudinal axis, measured from the centre of the foundation surface, for limit
axis states STR/GEO and for serviceability limit state.
Initial eccentricity Enter the eccentricity of the vertical load (Fs;v;d ) along the longitudi-
along longitudinal nal axis, measured from the centre of the foundation surface, for limit
axis states STR/GEO and for serviceability limit state.
Design load Enter the design value of the vertical load for limit states STR/GEO
and for serviceability limit state. Note that when using strip type ele-
ments (section 6.3.1), this load is the load in kN/m.

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Angle between Enter the angle (in the horizontal plane) which the horizontal load
load and (Fs;h;d ) makes with the longitudinal axis of the foundation element.
longitudinal axis
Initial eccentricity Enter the application height of the horizontal load (Fs;h;d ) mea-
to foundation level sured from the centre of the foundation base surface, for limit states
STR/GEO and for serviceability limit state.
Design load Enter the design value of the horizontal load for limit states STR/GEO
and for serviceability limit state. Note that when using strip type ele-
ments (section 6.3.1), this load is the load in kN/m.

6.3.3 Foundation plan

Use the Foundation – Pile Properties window to specify the foundation plan (layout).

Figure 6.10: Foundation – Foundation Plan window

The following information can be entered in this window:

Name Enter a name for the foundation element.

X Enter the x coordinate of the position of the centre of the foundation ele-
ment. This position is only relevant when Use interaction model has been
selected in the Calculation window (section 6.4.1). In that case the posi-
tion of the elements determines their mutual influence (interaction) on their
settlement.
Y Enter the y coordinate of the position of the centre of the foundation ele-
ment. This position is only relevant when Use interaction model has been
selected in the Calculation window (section 6.4.1). In that case the posi-
tion of the elements determines their mutual influence (interaction) on their
settlement.
Matching In this field select the type of element that should be placed at this posi-
type tion. The selection box is automatically filled with the types that have been
defined in the Foundation – Types window (section 6.3.2).
Angle Define the angle in the horizontal plane at which the foundation element is
placed in the foundation plan (0 degrees = North, 90 degrees = West). This
value has no relevance for round elements.
Matching Select the load that will act on the element placed at this position. The drop-
load down list contains the loads that were defined using the Loads sub-node of
the Foundation node of the tree view (section 6.3.2).
Matching Select the soil profile that represents the soil beneath this foundation ele-
profile ment. The drop-down list contains the profiles that were defined in the Soil
– Profiles window (section 6.2.2.3).

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Nearby Select the slope that should be linked to this position, interacting with the
slope foundation element also placed there. The drop-down list contains the
slopes that were defined in the Soil – Slopes window (section 6.2.3) as
well as the option None for foundations with no nearby slopes.

Use the toolbar on the left side of this window to edit the table:

Use this button to insert a row in the table.

Use this button to add a row to the table.

Use this button to delete a row from the table.

6.3.4 Top View Foundation

Select Top View Foundation under the Foundation node in the tree view to display this window.
Here the foundation element locations and types and the CPTs can be seen in plan view.
This view can also be used to check visually that there is no overlap between neighboring
foundation elements. This is relevant when the Interaction model as been selected in the
Calculation window (section 6.4.1)

Figure 6.11: Foundation – Top View Foundation window for Shallow Foundations (EC7-
NL) model

The button bar of this window allows the view to be manipulated in various ways:

Click this button to select objects using the cursor and to finish using any of the
other modes described below.

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Click this cursor to activate the pan mode. Click and drag the view to see a different
part of it.
Click this button to activate the zoom-in cursor. Then click on the part which is to
become the centre of the desired enlarged view. Repeat this step several times if
necessary.
Click this button to undo the last zoom-in step. If necessary, click several times to
retrace each consecutive zoom-in step that was made.
Click this button to select a rectangle for enlargement. The selected part will be
enlarged to fit the window. Repeat this step several times if necessary.
Click this button to measure the distance between two points. Click on one point
and the distance from there to the current mouse position is displayed in the panel
at the bottom of the view.
Click this button to undo the last zoom step.
Click this button to restore the original dimensions of the view.

6.4 Calculations
To start a calculation, click the Calculation node in the tree view. A window opens where:

⋄ in the top part of the window, various options are available (section 6.4.1);
⋄ in the bottom part of the window and information related to the type of calculation to be
performed can be specified (section 6.4.2).

Once all the information is correct, click Start to begin the calculation.

Figure 6.12: Calculation window for Shallow Foundations (EC7-NL) model

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6.4.1 Options for a Shallow Foundations calculation

Before performing a calculation, a number of options need to be specified. These will apply
to all shallow foundations.

Figure 6.13: Calculation window for Shallow Foundations (EC7-NL) model

In this part of the window the following information can be entered:

Rigidity of Indicate the rigidity of the superstructure according to NEN 9997-

superstructure 1+C2:2017 art. 7.6.1.1(c) as either Non-rigid or Rigid.
A restriction for the schematics is that for each calculation only (parts of)
buildings that can be regarded as either completely “rigid” or completely
“non-rigid” can be included in one schematic. If a building is regarded
as partly “rigid” and partly “non-rigid” (for instance a building with a rigid
core) at least two calculations must be carried out: one for the rigid part
and one for the non-rigid part. Also if a building consists of several dif-
ferent parts that can be regarded as rigid, a calculation must be made
for each part.
The reason for this restriction is the impossibility of determining the rel-
evant internal distances within the pile plan. Therefore the internal rota-
tions between rigid and non-rigid foundation elements cannot be calcu-
lated correctly. In the Background section of the manual, more informa-
tion on this topic (Rigid/Non-rigid) can be found.
Maximum Enter the settlement demand against which the verification takes place.
allowed As default values, the values given in NEN 9997-1+C2:2017 are pro-
settlement vided. It is possible to edit these values for either of the two limit states.
In case of limit state EQU/GEO, the default is an advised value, whereas
for serviceability limit state the default should be considered a minimum
value. If the values do not match the defaults this will be explicitly men-
tioned in the report.
Maximum Enter the relative rotation demand (between neighboring elements)
allowed against which the verification takes place. As default values, the values
relative given in NEN 9997-1+C2:2017 are provided. It is possible to edit these
rotation values for either of the two limit states. In case of limit state EQU/GEO,
the default is an advised value whereas for serviceability limit state the
default should be considered a minimum value. If the values do not
match the defaults this will be explicitly mentioned in the report.
γg(ST R/GEO) Here the user can enter its own value for γγ , the partial factor on the soil
unit weight for limit states STR/GEO. The default overruling value is 1.
γcoh Here the user can enter its own value for γc′ , the partial factor on effec-
tive cohesion c′ and undrained shear strength su . The default overruling
value is 1.

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γphi Here the user can enter its own value for γφ , the partial factor on friction
angle (tan φ). The default overruling value is 1.
γf und Here the user can enter its own value for γcu , the partial factor on
undrained shear strength su . The default overruling value is 1.
γg(SLS) Here the user can enter its own value for γγ , the partial factor on the soil
unit weight for serviceability limit state. The default overruling value is 1.
γCc Here the user can enter its own value for γCc , the partial factor on the
primary compression index Cc . The default overruling value is 1.
γCa Here the user can enter its own value for γCα , the partial factor on the
secondary compression index Cα . The default overruling value is 1.
Write Intermediate results can be written to a file by selecting this checkbox. It
intermediate must be born in mind that such a file can become very large. Note that
results this file is only available in Dutch.
Use interaction Select this checkbox to apply the interaction model when determining
model the settlement of a foundation element. The interaction model takes the
influence of all other foundation elements into account by superposition.
This model also allows for the calculation of the rotation between the
foundation elements (based on the centre point of the elements), pro-
vided no two elements are placed at the same position (i.e. the centre
point of the elements may not be the same). If the interaction model
is not applied, only the individual settlement of the individual element is
determined. This allows simultaneous calculation of several alternatives
for a foundation element. In this case, the centre points of the elements
are allowed to be at the same position.

6.4.2 Calculation options

Shallow Foundations offers three different calculation options (Figure 6.14):

⋄ Optimize Dimensions (section 6.4.2.1),

⋄ Maximize Vertical Loads (section 6.4.2.2),
⋄ and Verification (section 6.4.2.3).

Depending on the chosen option additional data can be entered in the Options sub-window.

Figure 6.14: Calculation options for the Shallow Foundations (EC7-NL) model

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6.4.2.1 Optimize Dimensions

Select Optimize Dimensions in the Calculation sub-window to automatically determine the
optimal dimensions of foundation elements, based on the specified forces. D-F OUNDATIONS
calculates these dimensions to the nearest 0.05 m between the limits of 0.20 m and of 200 m.

Figure 6.15: Calculation window, Options sub-window for an Optimize Dimensions calcu-
lation

In the Options sub-window the following information can be entered:

Keep length Mark this checkbox to only optimize the width of rectangular foundation
constant elements. When this box is unchecked both the width and the length of
rectangular elements are optimized.
Use the 5% The Dutch standard NEN 9997-1+C2:2017 uses a 20% limit to determine
limit instead which layers should be considered in the determination of the settlement.
of the 20% Only layers of which the increase in the effective vertical stress due to the
limit to placement of the foundation is larger than 20% of the original effective ver-
determine tical stress, are considered to have any effect on the settlement. All other
the layers are considered not to play any role in the settlement process.
settlement Deltares considers this to be a pretty rough approach and believes that a
5% limit is better (more layers play a part in the determination of the set-
tlement) and will lead to more accurate results. The default limit is 20% as
used in NEN 9997-1+C2:2017, but Deltares advises marking the checkbox
in order to use the 5% limit instead.

Note: When a calculation is started, any previous calculation results will be replaced. To
retain previous results, print the results or make a copy of the project files. Alternatively, set
the default action to Always Save As instead of Always Save for the Save on Calculation
option on the General tab in the Program Options window (Tools menu). In that case a ‘Save
As’ dialog will automatically appear each time a calculation is started.

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6.4.2.2 Maximize Vertical Loads

Select Maximize Vertical Loads in the Calculation sub-window to calculate the maximum al-
lowed vertical load (without eccentricities) on the foundation elements, based on the specified
dimensions. The program calculates these values to the nearest 0.01 kN with a minimum of
0.05 kN.

Note: Any horizontal load that has been entered will be fully included in the calculations
performed with this option.

Figure 6.16: Calculation window, Options sub-window for a Maximize Vertical Loads cal-
culation

In the Options sub-window the following information can be entered:

Load factor To determine the maximum allowed vertical load, both limit state
limit state STR/GEO and serviceability limit state are checked. Normally, the loads
STR/GEO or for these limit states differ as the loads for limit state STR/GEO (Dutch:
serviceability ‘uiterste grenstoestand’) are larger than serviceability limit state (Dutch:
limit state ‘bruikbaarheidsgrenstoestand’). This difference can be defined here as a
load factor:
Force in serviceability limit state = load factor × Force in limit state
STR/GE0.
The exact load factor should be determined based on NEN 9997-
1+C2:2017 but typically this factor would be 0.833.
Use 5% limit The Dutch standard NEN 9997-1+C2:2017 uses a 20% limit to determine
instead of which layers should be considered in the determination of the settlement.
20% limit Only layers, of which the increase in the effective vertical stress due to
the placement of the foundation is larger than 20% of the original effective
vertical stress, are considered to have any effect on the settlement. All
other layers are considered not to play any role in the settlement process.
Deltares considers this to be a pretty rough approach and believes that
a 5% limit is better (more layers play a part in the determination of the
settlement) and will lead to more accurate results. The default limit is
20% as used in NEN 9997-1+C2:2017, but Deltares advises marking the
checkbox in order to use the 5% limit instead.

Note: When a calculation is started, any previous calculation results will be replaced. To
retain previous results, print the results or make a copy of the project files. Alternatively, set
the default action to Always Save As instead of Always Save for the Save on Calculation
option on the General tab in the Program Options window (Tools menu). In that case a Save
As dialog will automatically appear each time a calculation is started.

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6.4.2.3 Verification
Select Verification in the Calculation sub-window to start the calculations needed to perform a
complete verification according to NEN 9997-1+C2:2017. The results of this option are shown
in the report file. For more information about viewing results, refer to chapter 7.

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 7 View Results
If errors are found in the input, no calculation can be performed and D-F OUNDATIONS opens
the Log Messages window (section 3.3.3) displaying more details about the error(s). Those
errors must be corrected before performing a new calculation.

In the tree view, the Results node contains all or some of the following options, depending on
the model used:

⋄ section 7.1 Load-Settlement Curve

⋄ section 7.2 Design Results
⋄ section 7.3 Intermediate Results
⋄ section 7.4 Report

7.1 Load-Settlement Curve/Load-Rise Curve

The Load - Settlement Curve/Load-Rise Curve window, reached by selecting the Load-Settlement
Curve (for model Bearing Piles (EC7-NL)) or Load-Rise Curve (model Tension Piles (EC7-
NL)) sub-node under the Results node in the tree view, displays the Load/Settlement curve(s)
or Load/Rise curve(s) resulting from the Verification calculations of the Bearing Piles (EC7-NL)
model and the Tension Piles (EC7-NL). When a defined problem fully meets the verification
requirements, the curve can be viewed for both limit states. However, if the problem does not
fulfill the requirements (see the report) it is possible that only one of the curves can be viewed,
or none at all. When loads are too big (and the construction collapses) it is not possible to
draw a curve. When the Verification calculation type is performed together with the Design
calculation, the result of the calculation that will be shown refer only to the deepest calculation
and not to the pile tip level. In addition, it is important to note that the curve produced in the
case of Tension Piles (EC7-NL) calculation has a base side that is always equal to zero.

Figure 7.1: Load / Settlement Curve window Bearing Piles (EC7-NL)

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Figure 7.2: Load / Rise Curve window Tension Piles (EC7-NL)

Please note that for constructions with a non-rigid superstructure, the results represent the
decisive case. For constructions with a rigid superstructure it is in fact not possible to present
a decisive case as the result is the average value of all cases. As the average cannot be
displayed, the worst case is displayed in order to give the user some idea of the settlement.

The button bar of this window allows the view of the load-settlement curve to be manipulated
in various ways:

Click this button to finish using any of the other modes described below.
Click this cursor to activate the pan mode. Click and drag the view to see a different
part of it.
Click this button to activate the zoom-in cursor. Then click on the part which is to
become the centre of the desired enlarged view. Repeat this step several times, if
necessary.
Click this button to undo the last zoom-in step. If necessary, click several times to
retrace each consecutive zoom-in step that was made.
Click this button to select a rectangle for enlargement. The selected part will be
enlarged to fit the window. Repeat this step several times, if necessary.
Click this button to undo the last zoom step.
Click this button to restore the original dimensions of the view.
Click this button to display the result for limit state GEO.
Click this button to display the result for serviceability limit state.

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Table 7.1: Overview of the displayed design results

Model Calculation Option Chart Text

type
Bearing Preliminary Indication of bearing capacity Yes Yes
Piles Design Bearing capacity at fixed pile tip levels No Yes
(EC7-NL) Pile tip levels and net bearing capacity No Yes
Verification Design Yes Yes
Complete No No
Tension Design Indication of bearing capacity Yes Yes
Piles Bearing capacity at fixed pile tip levels No Yes
(EC7-NL) Pile tip levels and net bearing capacity No Yes

7.2 Design Results

Click on Design under the Results node in the tree view to open the Results – Design window.
The displayed design results will vary with the type of calculation that has been carried out,
as shown in Table 7.1.

Note: For Bearing Piles (EC7-NL) / Verification / Complete no design results can be viewed.
Also note that the Shallow Foundations (EC7-NL) model does not offer this option.

The results can be displayed in text format or in chart format by clicking the appropriate tab to
adjust the display type.

The Chart tab of the Design Results window has the header of Figure 7.3.

Figure 7.3: Design Results window – Header

In this header the following options can be selected:

CPT Use the drop-down list to select to display the chart for either all CPTs or a
single CPT.
Force Use the drop-down list to select the appropriate force to be displayed.
Pile type Use the drop-down list to either select a chart with the results for all pile
types together or to display the results for a single pile type.
Pile group Use the drop-down list to select the pile group for which the results should
be displayed. The piles belonging to one group have equal capacity and
the group’s content is displayed both in the text option and in the report.

The Text tab of the Design Results window has the header of Figure 7.4.

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Figure 7.4: Design Results window – Header

In this header the following options can be selected:

Filter results If required, the displayed results can be filtered. Enter a Lower limit and/or
an Upper limit as filter criteria. The checkbox Apply filter is used to switch
the filter on and off.
Order Select the appropriate toggle button to sort the results by either Depth or
results by CPT.

Note: The actual options provided in the headers may vary between models and calculation
options.

7.3 Intermediate Results

After a successful calculation, the intermediate results can be saved in the optional intermedi-
ate results file (*.for) if the option Write intermediate results has been selected in the Calcula-
tion window. The contents of this file will reflect the progress of this calculation process. The
content of this intermediate results file (and the output file) depends on the calculation type:

⋄ Refer to section 7.3.1 for the Bearing Piles (EC7-NL) model;

⋄ Refer to section 7.3.2.1 for the Shallow Foundations (EC7-NL) model.

The intermediate results of the calculations are available only in text format and currently only
in Dutch.

7.3.1 Intermediate Results for Bearing Piles (EC7-NL)

A description is included in the sections below for each calculation step of the most extensive
configuration of the *.for file, using the Bearing Piles Calculation Type Verification with Com-
plete calculation options in the Calculation window. With this option, all limit states are run
through during calculation. The intermediate results for each calculation step for each limit
state are saved in the file. The calculation results are explained for:

⋄ section 7.3.1.1 Limit state EQU (calculation per CPT)

⋄ section 7.3.1.2 Limit state GEO and serviceability (calculation per CPT per pile)

Using the Preliminary Design option in the Bearing Piles Calculation Type sub-window in the
Calculation window, only limit state EQU and the negative skin friction for limit state GEO
are calculated for each calculation step. With this type of calculation, therefore, for each
calculation step the *.for file is limited to the intermediate results of this these two items.

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7.3.1.1 Limit state EQU (calculation per CPT)

The following is executed for limit state EQU (calculation per CPT):

Per CPT:
qc;I;gem Average value of cone resistance for trajectory I.
qc;II;gem Average value of cone resistance for trajectory II.
qc;III;gem Average value of cone resistance for trajectory III.
Deq Equivalent diameter of the pile.
αp Pile class factor.
β Pile base form factor.
s Factor for cross-section form of the pile base.
qb;max;i Maximum cone resistance around pile tip in the case of CPT i (before
(voor reductie) reduction to max. 15 MPa).
qb;max;i Maximum cone resistance around pile tip in the case of CPT i (after
(na reductie) reduction to max. 15 MPa).
Rb;cal;max;i Maximum (calculated) pile tip resistance in the case of CPT i.
Rs;cal;max;i Maximum (calculated) pile shaft resistance in the case of CPT i.
Rc;cal;max;i Maximum (calculated) bearing capacity of the pile in the case of CPT i.

End results:
ksi3 Factor ξ3 from NEN-EN-1997-1-NB (adopted in NEN 9997-1+C2:2017
Tables A.10a and A.10b).
ksi4 Factor ξ4 from NEN-EN-1997-1-NB (adopted in NEN 9997-1+C2:2017
Tables A.10a and A.10b).
Rc;cal;gem Average bearing capacity of the pile calculated using ξ3 .
(met ksi3)
Rc;cal;min Minimum bearing capacity of the pile calculated using ξ4 .
(met ksi4)

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ksi... is used The actual factor ξ (ξ3 or ξ4 ) used in the calculation.

Rb;k Characteristic value of pile tip resistance.
Rs;k Characteristic value of pile shaft resistance.
Gamma_b Partial resistance factor of pile tip from NEN-EN-1997-1-NB (adopted in
NEN 9997-1+C2:2017 Tables A.6-A.8).
Gamma_s Partial resistance factor of pile shaft from NEN-EN-1997-1-NB (adopted
in NEN 9997-1+C2:2017 Tables A.6-A.8).
Rb;d Design value of pile tip resistance.
Rs;d Design value of pile shaft resistance.
Rc;d Design value of pile bearing capacity.

7.3.1.2 Limit state GEO and serviceability limit state (calculation for each CPT for each pile)
The following is executed for both limit state GEO and serviceability (calculation per CPT per
pile):

Negative skin friction per CPT per pile:

Fnk;k Characteristic value of the friction force as a result of negative skin friction.
gamma;f;nk Partial load factor γf ;nk .
Fnk;d Calculation value of the friction force as a result of negative skin friction.
sneg Settlement as a result of the negative skin friction if the expected ground
level settlement (mvz ) is between the limits 0.02 < mvz ≤ 0.10 m; other-
wise sneg = 0 applies.

Per CPT per pile for the settlement calculation:

Fc;tot;i Calculated value of the total load on the pile head.

Rb;cal;max;i;d Maximum design value of pile tip resistance.
Rs;cal;max;i;d Maximum design value of pile shaft resistance.
s2 Calculated value of the settlement caused by compressing the layers under
pile tip level.
Rb;i;d Calculated value of the dominant force in the pile tip (based on pile dis-
placement, see NEN 9997-1+C2:2017 Figures 7.n and 7.o).
sb Calculated value of the settlement of the pile tip as a result of the load on
the pile.

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sel Calculated value of the settlement of the top end of the pile with respect to
the pile tip as a result of the elasticity of the pile itself.
s1 Calculated value of the settlement of the top end of the pile.
s Calculated value of the settlement of the top of a foundation element.

End results:

Maximale The number of both the CPT and the pile where the maximum
schachtspanning . . . shaft tension occurs.
Sigma_max_schacht_GEO The maximum occurring shaft tension.
Maximale zakking. . . The number of both the CPT and the pile where the maximum
settlement occurs.
s_d;max The maximum occurring settlement (for non-rigid structures)
or the average settlement (for rigid structures).
Beta_dGEO The maximum occurring relative rotation.

7.3.2 Intermediate Results for Shallow Foundations (EC7-NL)

The following is a description of the intermediate results using the Verification option in the
Calculation window. When the Optimize Dimensions and Maximize Vertical Loads options
in the Calculation window are used, the file is the same as far as printed parameters are
concerned, although the content is now incorporated in the file for each iteration step in the
calculation. The intermediate results are saved in the file for each calculation step (= for each
foundation element) and for each limit state. The calculations are explained below for:

⋄ section 7.3.2.1 Limit state EQU

⋄ section 7.3.2.2 Limit states GEO and serviceability limit state

7.3.2.1 Limit state EQU

The following is executed (these parameters are used/calculated) for limit state EQU:

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Bearing capacity, undrained behavior:

Calculation case:

Berekeningsgeval The type of calculation to be executed for the determination of the

soil parameters, between cases A, B or C (see art. 6.5.2.2(f) of
NEN 9997-1+C2:2017).

Determining initial effective surface A’ on specified foundation level:

Vd Calculation value of the vertical load.

Vg;v;d Calculation value of the extra load of soil when the foundation level is displaced
due to punching.
b′ Effective width of the foundation element.
l′ Effective length of the foundation element.
Zu Foundation level valid at this moment in the calculation.
ae Influence width.
te Influence depth.

Redefinition of A’ when punching occurs:

Vd Calculation value of the vertical load.

Vg;v;d Calculation value of the extra load of soil when the foundation level is displaced
due to punching.
Bcor Correction of the width of the foundation element when the foundation level is
displaced due to punching (dz × tan 8◦ ).
Lcor Correction of the width of the foundation element when the foundation level is
displaced due to punching (dz × tan 8◦ ).
eHcor Correction of the arm of the horizontal force when the foundation level is displaced
due to punching.
Bef _p Effective width of foundation element in the case of punch.
Lef _p Effective length of foundation element in the case of punch.
Zu Foundation level valid at this moment in the calculation.

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Determination bearing capacity (NEN 9997-1+C2:2017 art. 6.5.2.2(g)):

cu;d Calculation value of undrained shear stress.

ic Reduction factor for gradient of the load.
sc Form factor for the effect of the cohesion.
Sv;z;d Calculation value of original vertical effective stress at depth z.
Smax;d Calculation value of maximum foundation pressure.
Lambdac Correction factor for any ground level gradient for the effect of cohesion.
Lambdaq Correction factor for any ground level gradient for the effect of soil cover.
Lambdag Correction factor for any ground level gradient for the effect of effective volu-
metric weight of the soil under the foundation surface.
ae Influence width.
te Influence depth.
uRd Maximum calculation value of the undrained vertical bearing capacity.
Ftrek Tensile force per linear m that the foundation can absorb in the case of squeeze
(additional information, no verification value).
sqRd Calculation value of the vertical bearing capacity in the case of squeeze.
Vd+g;v;d Maximum calculation value of the total vertical load (including extra load due
to punch, Vd + Vg;v;d ).

Bearing capacity, drained behavior:

Calculation case:

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Berekeningsgeval The type of calculation to be executed for the determination of the soil
parameters, between cases A, B or C (see art. 6.5.2.2(h) of NEN 9997-
1+C2:2017).

Parameters/Results without punch (NEN 9997-1+C2:2017 art. 6.5.2.2(i)):

ic Reduction factor for the gradient of the load on the effect of the cohesion.
iq Reduction factor for the gradient of the load on the effect of the soil cover.
iγ Reduction factor for the gradient of the load on the effect of the effective weight
of the soil under the foundation surface.
sc Form factor for the effect of the cohesion.
sq Form factor for the effect of the soil cover.
sg Form factor for the effect of the effective weight of the soil under the foundation
surface.
Nc Bearing capacity factor for the effect of the cohesion.
Nq Bearing capacity factor for the effect of the soil cover.
Ng Bearing capacity factor for the effect of the effective weight of the soil under the
foundation surface.
Sv;z;d Calculation value of the original vertical effective stress at depth z.
Smax;d Calculation value of the maximum foundation pressure.
Vd Calculation value of the vertical load
Vg;v;d Calculation value of the extra load of soil when the foundation level is displaced
due to punch.
Bcor Correction of the width of the foundation element when the foundation level is
displaced with respect to punch (dz × tan 8◦ ).
Lcor Correction of the width of the foundation element when the foundation level is
displaced with respect to punch (dz × tan 8◦ ).
eHcor Correction of arm of horizontal force when the foundation level is displaced with
respect to punch.
Bef Effective width of the foundation element.
Lef Effective length of the foundation element.
Zd Foundation level valid at this moment in the calculation.
ce;d Calculation value of the (weighed) cohesion.
fe;d Calculation value of the (weighed) effective angle of friction.
ge;d Calculation value of the (weighed) effective volumetric weight of the soil under
the foundation surface.
dRd Calculation value of the drained vertical bearing capacity.
Vd+g;v;d Maximum calculation value of the total vertical load (including extra load due to
punch, Vd + Vg;v;d ).

Parameters/Results WITH punch:

These match the parameters for the drained situation without punch.

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Shear, undrained behavior:

Most of the parameters match the parameters for bearing capacity, undrained behavior. Ad-
ditional parameters are:

uRd Calculation value of the undrained shear resistance.

Hd Calculation value of the horizontal load.

Shear, drained behavior:

dRd Calculation value of the drained shear resistance.

Hd Calculation value of the horizontal load.

Stability checks:

Min b′ Minimum value of the effective width determined during the calculations.
′
Min l Minimum value of the effective length determined during the calculations.
fgem;d Calculation value of the angle of internal friction of the critical soil layer.

7.3.2.2 Limit states GEO and serviceability limit state

The following are executed for both limit state GE0 and serviceability limit state:

Determining initial effective surface Aef :

Vd Calculation value of the vertical load.

Vg;v;d Calculation value of the extra load of soil when the foundation level is displaced
with respect to punch.
b′ Effective width of the foundation element.

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l′ Effective length of the foundation element.

A first approach to the settlement to determine the 20% limit layer (NEN 9997-1+C2:2017).
This is the deepest layer where the increase in vertical force is still greater than 20%. To gain
an impression of the sensitivity of the 20% limit, a 5% limit layer has also been determined.
This should be seen as additional information. The first approach is based on Fs;v;d as the
point load.

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layer no. Layer in the soil profile, counting down from the surface.
depth Level in m at which the effective stresses have been determined (middle of
the relevant layer).
dsigmav;z;d Calculation value of the increase in effective stress at depth z .
sigmav;z;o;d Calculation value of the original vertical effective stress at depth z .
percentage Increase in stress as percentage of the original stress or 100 × dsig-
mav;z;d / sigmav;z;o;d.
20% laag Number of the lowest layer for which the percentage is above 20%.
5% laag Number of the lowest layer of which the percentage is above 5%.

Calculation of the settlement:

The effective foundation surface (Aef ) is divided here into 256 equal sections. A point load
of the size Fs;v;d /256 is located on each plane. This is aimed at a better way of finding the
increase in stress (uniform load approach).

layer no. Number of the layer in the soil profile.

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depth Level in m at which the effective stresses have been determined (middle of
the relevant layer).
dsigma;v;z;d Recalculated calculation value of the increase in effective stress at depth z.
sigma;v;z;o;d Calculation value of the original vertical effective stress at depth z.
e Void ratio.
e0 Initial void ratio.
s1 Calculation value of the primary settlement (w1;d ) based on calculation for
s1;gd all layers with stress increases greater than or equal to 20%. If the layer
number has an asterisk it involves an additional, purely informative value for
the primary settlement (w1;gd ) based on calculating settlements for layers
with stress increases greater than or equal to 5%. Comparing w1;d with
w1;gd produces an indication for the sensitivity of the layer classification
related to the primary settlement.

To indicate the accuracy of the settlement calculation:

Max. dsigma;v;z;d as percentage of the effective foundation pressure = 98%

For purely vertically loaded foundations, this percentage should be above 80% to have an
accurate calculation. When horizontal loads are also working on the foundation, the effective
foundation area is reduced by the horizontal load and the percentage here will drop consid-
erably. So, in case of horizontal loading this percentage does not provide a directly usable
indication.

Overview of the calculated settlements:

s1 and s1;gd See above.

s2 Calculation value of secondary settlement.
s Calculation value total settlement (s1 + s2 ).

7.4 Report and report content selection

7.4.1 Report
The report file is made available each time a calculation has been performed successfully.
It can be viewed by clicking on the Report sub-node in the Results node, in the tree view.
The report repeats the input and presents the results of the calculation. If the calculation
process has been aborted because of calculation errors or input errors, a description of the
encountered errors will be displayed in the report.

7.4.2 Report Options

On the menu bar, click Results and then choose Report Options to open the Report Options
window. In this window the start number of the report document can be defined as well as
the text preceding the page number in the footer of the report. Finally, an option is provided

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to have the names of your Cone Penetration Tests preceded with a number to help identifying
them in case of long similar names. These long similar names are shortened when displayed
in tables in the report. This is done to keep the width of the tables within the limits of the page
width.

Figure 7.5: Report Options window

Page start number The starting number of the report footer.

Show date Show date/time information on frontpage and report
footer.
User defined When this checkbox is unmarked the word Page will
appear next to the page number in the report. How-
ever, when the checkbox is selected the word pre-
ceding the page number can be defined by the user.
Text Text preceding the page number in the footer.
Show warning when report is too Enable/disable warning when report is too wide to
wide to fit in print area fit in print area (shown when a report is generated).
Use numbering for CPTs Precede names of Cone Penetration Tests (CPTs)
with numbers.

7.4.3 Report content selection

Select Report Selection from the Results menu at the top of the screen in order to open the
Report Selection window.

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Figure 7.6: Report Selection window

In this window the required content of the report can be chosen by marking the checkboxes.
Click Select All to mark all of the checkboxes and Deselect All to un-mark all of the check-
boxes. Clicking OK will apply this selection to the report.

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 8 Tutorial 1: Preliminary Design of Bearing Piles for a Storehouse
This first tutorial considers the preliminary design of a pile foundation for a storehouse.

The objectives of this exercise are:

⋄ To learn the steps needed to enter relevant data for a preliminary design, such as soil
and pile properties.
⋄ To calculate the bearing capacity with depth of a single pile, just for preliminary design
purposes.

This tutorial is presented in the file Tutorial-1.foi.

8.1 Introduction
A new storehouse needs to be constructed, in a delta environment. In the light of the ex-
pected loads acting on the foundation and the soil profiles usually found in a delta, a pile
foundation will be needed. Two cone penetration tests (CPTs) have already been carried out
at the proposed location. In order to get a first impression of an appropriate pile type and
the corresponding pile length, a preliminary design will be performed using D-F OUNDATIONS,
based on a first estimate of the required load capability (400 kN per pile). Two different pile
types will be considered: a square 250 mm prefab concrete pile, and a concrete pile with an
enlarged base.

Figure 8.1: Storehouse construction in a delta environment (Tutorial 1)

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8.2 Setting up a new project

1. Start D-F OUNDATIONS and create a new project by clicking the button on the toolbar. The
Project Properties – Description window is displayed as indicated in Figure 8.2.
2. Enter the text <Tutorial 1 for D-F OUNDATIONS > for Title 1, and <Bearing Piles calculation
with concrete piles> for Title 2. These titles identify the project, and are displayed in all
reports and graphs printed.

Figure 8.2: Project Properties – Description window

3. Click to save the project. In the Save As dialog that opens, browse to a folder where the
tutorial has to be saved and type <Tutorial-1> in the input field File name.
4. Click Save to close the window.

An empty project, identified by its name and description, has now been created. The following
sections of this tutorial describe how to enter the input needed for the preliminary design of
the piles.

8.3 Construction sequence

5. Click on the Construction Sequence node under Project Properties in the tree view on the
left of the screen. This will open the corresponding window where the relative timing of
CPTs with respect to the installation of the piles can be specified. This execution time
is needed to determine whether certain exceptions made in NEN 9997-1+C2:2017 apply,
see section 4.2.
6. Select CPT – Excavation – Install since the two cone penetration tests were done prior to
the design of the foundation.

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8.4 Creating soil profiles

For the design of a foundation in D-F OUNDATIONS, CPTs data are needed. These are inter-
preted to give the soil profile data.

The results of the two cone penetration tests carried out at the project site are shown in
Figure 8.3 and Figure 8.4. The results show that competent bearing sand for the foundation
starts at a reference level of approximately -13 m. It can therefore be initially concluded that
the piles need to have a length of more than 13 m minus ground level. It can also be concluded
that the skin friction along the pile will switch from negative friction to positive friction at this
level, if negative friction is to occur.

7. To import the two CPTs, click the Profiles node under Soil in the tree view. As there are
currently no soil profiles in the model, D-F OUNDATIONS automatically opens the Import CPTs
from file dialog.
8. Select the file <Tutorial-1 CPT 01.gef> and click Open. D-F OUNDATIONS reads the selected
file and opens the Soil – Profiles window (see Figure 8.5). A new subnode is formed under
Profiles bearing the name of the CPT.
9. To import the second CPT click the Profiles node again and select Import under Action.
10. The Import CPTs from file dialog opens as before; this time select Tutorial-1 CPT 02.gef,
and click Open.

Figure 8.3: CPT 01 (Tutorial 1)

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Figure 8.4: CPT 02 (Tutorial 1)

11. Click the name of one of the CPTs in the tree view to open its corresponding Soil – Profiles
window. In this window, two soil profiles are drawn. The left profile is an interpretation
of the imported CPT, with the CPT data drawn to the left of it. The interpretation method
that is selected as the default method is the NEN rule (based on NEN 9997-1+C2:2017
Table 2.b). The default minimum layer thickness is 0.10 m, which results in a soil profile
with many thin layers.
12. Check that NEN rule is selected for the CPT Rule. In order to make a visual inspection of
the interpreted soil profile feasible, set the Min. layer thickness to <0.20 m>. The right-
hand profile is the profile that may be edited by the user. It is also presented in tabular
format at the right-hand side of the Soil – Profiles window. This profile is used as the input
profile for calculations.
13. Click the button to copy the new CPT interpretation to right-hand profile.
14. Repeat this process for the other CPT by selecting the other CPT in the tree view, selecting
NEN rule, setting the Min. layer thickness to <0.20 m> and clicking the button again.

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Figure 8.5: Soil – Profiles window

The profiles that have resulted from this interpretation will be used for the remainder of this
tutorial (the right-hand profile), and will function as input for the preliminary design calcula-
tions.There is one more parameter that needs to be inputted here, namely the level in the soil
profile where the skin friction changes from negative into positive. Based on a visual inspec-
tion of the CPT, it can be assumed that this is at reference level -13 m, at the top of the bearing
sand layer and just below the soils that are susceptible to settlement.

15. Switch to the Additional Data tab and fill in this value in the input field Top of positive skin
friction zone and in the input field Bottom of negative skin friction zone. The default values
provided for the other parameters on this tab are as required for this design case and need
not to be changed.

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Figure 8.6: Soil – Profiles window, Additional Data tab

16. Switch from one profile to the other by clicking in the tree, and apply this data to the other
profile as well. The input of soil data needed for these basic design calculations is now
complete.

Optionally, the actual soil parameters used in the calculation can be reviewed under the node
Materials.

8.5 Defining the foundation

The next step is to input data on the foundation to be used. For a preliminary design the pile
type needs to be defined.

17. To define the pile types for this tutorial, click the Pile Types node in the tree view. When
this node is selected for the first time, D-F OUNDATIONS creates a new pile type and shows
its properties in the Foundation – Pile Types window.

Figure 8.7: Foundation – Pile Types window

The first pile type is a rather simple one: a square prefabricated concrete pile, with a base
width of 250 mm. Because rectangular prefabricated concrete piles are the default in D-F OUNDATIONS,
only the dimensions of the pile need to be filled in to finish defining the first pile type.

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18. In the two input fields Base width and Base length, fill in <0.25 m>.

The second pile type, a concrete pile with enlarged base, is not as straightforward to input as
the first one. Especially because in this case, the pile manufacturer advises to use a specific
value for αρ (αρ = 0.88).

19. To create a new pile type, select the Pile Types node in the tree view, and click New in the
Pile Types window. A copy is made of the previous pile type.

Figure 8.8: Creating new pile types

In this window, enter/edit the data as described below:

20. Click the picture of Rectangular pile with enlarged base. After selecting this option, the
parameters that may be entered appear in the lower half of the input window.
21. Enter the values that are listed below:

For base width av: 0.4 m;

For base length bv: 0.42 m;
For height H: 1.2 m;
For shaft width as: 0.32 m;
For shaft length bs: 0.32 m;

22. Select <User defined (vibrating)> as the Pile Type.

23. Select <Bored pile (drilling mud, uncased borehole)> under αs sand/gravel to cause the
automatic selection of the pertinent pile factor for shaft friction in sand and gravel.
24. Select <According to the standard> under αs clay/loam/peat to allow the pile factor for
shaft friction in clay loam and peat to be determined according to the NEN 9997-1+C2:2017
standard.
25. Select <User defined> for αp , the pile factor for the point, and enter the value <0.88> in
the input field that appears.
26. Select <1> under Load-settlement curve.
27. Mark the As Prefab checkbox.
28. Select <Concrete> as the Material. The Young’s modulus is given automatically.
29. Select <Synthetic> as the Slip layer.

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Figure 8.9: Foundation – Pile Types window, Selecting dimensions

See section 4.4.1 for explanation of the dimensions. These dimensions are also shown in the
diagram on the right. Two different pile types have now been defined. Later on, calculations
will be made for both types.

8.6 Entering the context

The soil profiles and pile types needed for the preliminary design calculation have now been
defined. However, some information about the location of the piles and about various condi-
tions that will effect the pile loading still needs to be entered. For instance, the actual piles
and their positions have not yet been specified.

30. To enter a pile, click the Pile Properties node in the tree view.
31. In the window that opens, simply click the first row to enter a pile. Note that the X and Y
co-ordinate and the pile head level by default are derived from the CPT data available. For
this case, these default values are ok.
32. Set the Pile Head Level to <0 m>.

This example assumes that within the building area the soil level will be raised with 0.5 m by
adding a layer of sand. This will be done after driving the piles to improve the accessibility of
the site. This embankment corresponds to a surcharge load of 9 kN/m2 .

33. Enter <9> in the Surcharge column in the table.

More piles do not need to be added at this stage. For a preliminary design a single pile is
considered in default. A pile plan can only be considered in a design stage.

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Figure 8.10: Foundation – Pile Properties window

8.7 Making a preliminary design

The next step is to perform a preliminary design calculation, for which only a single pile is
considered.

34. Switch back to the Soil – Profiles window in order to view the soil profiles. This will allow
the depth range over which the calculation should take place to be determined. The depth
range of interest for this design consists of the layers of loam and sand that lie between
reference levels -13 m and -22 m because between these levels the soil layer seems able
to bear our foundation (it has a relatively high qc ).

Figure 8.11: Profiles window, Detail of the Soil

To make sure to find the proper level, the actual trajectory is stretched a bit. So it starts at
-10 m and ends at -25 m. Please note that CPT-data needs to be available to at least 5 times
the pile diameter below the deepest pile tip level (in this case -25 m).

35. Switch to the Calculation window and select Preliminary Design for Calculation Type and
Indication Bearing Capacity under Calculation.

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36. Mark the Write intermediate results (Dutch) checkbox to make it possible to view the inter-
mediate results file.
37. Enter a Trajectory to Begin at <-10 m> and End at <-25 m>, with an Interval of <0.5 m>.

Figure 8.12: Calculation window

38. Press the Start button to begin the calculation.

Note: For preliminary design calculation always a single pile is considered, whatever the plan
of piles has been filled in previously in the Pile Properties window.

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8.8 Results

Figure 8.13: Design Results window, Chart tab

When the calculation process has finished, the bearing capacity with depth of the pile tip is
displayed in graphical format, for both pile types and both soil profiles. Follow the steps given
below to inspect the results for the pile types one by one.

39. First, select pile type Rect 250 × 250 from the list of pile types. The two lines in the graph
that result give the bearing capacity for both soil profiles. A bearing capacity of 400 kN is
needed, which is achieved at a level of -17.7 m.
40. Then select pile type RectEnl 400 × 420 from the list of pile types, and read the values for
the bearing capacity for both profiles. Now, the required bearing capacity is achieved at a
level of -14.4 m.

Note: For a preliminary design and consequently a single pile the default ξ3 and ξ4 -factors
that are taken into account are the ξ3 and ξ4 factors for two CPTs (n = 2) and non-rigid
structure (also see NEN 9997-1+C2:2017 Table A.10a). For a rigid superstructure, lower ξ3
and ξ4 factors are allowed; resulting a higher bearing capacity for the same piles at the same
depth when verifying the preliminary design later on. Most probably the specifications for this
foundation, assuming a rigid superstructure, are met at a reference level of -14 m.

Note: The design graph shows the level of the piles; as the surface level is at about -0.8 m,
these needs to be taken into account for the length of the piles.

It can be concluded that the foundation can be constructed either using rectangular piles with
a length of at least 17.7 - 0.8 = 16.9 m, or with piles with enlarged base with a length of
14.4 - 0.8 = 13.6 m. The final choice of pile type may depend on several factors, such as
bearing capacity, expense of the piles or usefulness of the pile type compared to other pile
types available.

In Tutorial 3 in chapter 10 this project will be continued, looking at the verification rather than
the preliminary design.

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8.9 Conclusion
This tutorial has demonstrated how to enter the data required for a simple preliminary design
calculation. The calculation option Preliminary design: Indication bearing capacity allows the
minimum pile length to be determined, by finding the bearing capacity as a function of depth
for a specified single pile.

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9 Tutorial 2: Obsolete (Previously: Feasibility of Bearing Piles for a
Storehouse)
This tutorial is no longer available, since the Feasibility option was removed in release 21.1.

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10 Tutorial 3: Verification of Bearing Piles for a Storehouse
A preliminary design step can only be used in order to obtain a first impression of the bearing
capacity with depth for a single pile foundation. In this tutorial D-F OUNDATIONS will be used to
verify the design from the first tutorial to see if it is actually correct.

The objectives of this tutorial are:

⋄ To learn how to input a grid of piles.

⋄ To verify the preliminary design from Tutorial 1 (chapter 8).

This tutorial is presented in the files Tutorial-3a.foi and Tutorial-3b.foi.

10.1 Introduction to the case

In the first tutorial, a preliminary design for a storehouse foundation was made based on the
results of two CPTs, and two given pile types. It was concluded that square concrete piles
with a length of 17.7 m would probably be sufficient for a rigid superstructure (section 8.8).
The necessary requirements for assuming a rigid superstructure are given in NEN 9997-
1+C2:2017 art. 7.6.1.1(c).

Given the measurements of the storehouse, a pile plan consisting of 36 piles in a 6×6 grid
has been devised (Figure 10.1). The piles are 2 m apart from each other.

Figure 10.1: Boring, front and top views of the pile plan (Tutorial 3)

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Knowing the pile plan and all details about the building, the required design loads per pile
are set, by the constructor of the building, at 400 kN for limit state STR/GEO and 300 kN for
serviceability limit state (more information on the limit states can be found in section 16.2).

10.2 Preparing a new project

1. Click Open from the File menu and select the project Tutorial-1.
2. Select Save As in the File menu and save the project as <Tutorial-3a> before continuing
this tutorial.
3. In the Project Properties – Description window, change Title 1 and Title 2 to respectively
<Tutorial 3 for D-F OUNDATIONS > and <Verification of Bearing Piles for a Storehouse>.

10.3 Defining the correct pile tip level(s)

The first step is to define the correct pile tip levels.

4. Switch back to profile 01 by selecting its corresponding node in the tree view. In the Soil –
Profiles window that opens, select the second tab: Additional Data.
5. Fill in the value of reference level <-17.7 m> in the input field Pile tip level. Note that this
value of -17.7 m represents the pile tip level.
6. Switch to profile 02 and fill in the same value.

10.4 Defining the pile plan

The pile types to be used and the length of the piles have already been defined/determined
in the previous tutorial. It now remains to define the pile plan by entering the pile locations,
along with some additional data.

7. Click the Pile Properties node in the tree view.

A window opens with a table containing the single pile that was entered in the previous tuto-
rial. Based on the maximum bearing capacity of the piles and the weight of the building, the
constructor has decided to use a grid of 36 piles, evenly spaced in both the X- and Y direc-
tions. The Generate Pile Grid option offers a fast way of entering a regular grid of identical
piles.

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Figure 10.2: Pile Grid window

8. Click the Generate Pile Grid button to open the Pile Grid window. In this window, mark
the checkbox for Set relative to profile. Then enter the location of the lower left pile in the
plane by selecting profile 01 as reference. Its coordinates are X = 120000 m; Y = 50000 m.
By leaving the X- and Y coordinate at 0.00, the piles will be generated with 120000 and
50000 m as base. Enter the distance between two piles (2 m in both directions).
9. Specify the number of piles in both directions (6 piles) and the level of the pile head (0 m
below the reference level). Note that a level below reference implies a negative value.
10. Fill in a Design value of load on pile of <400 kN> for Limiting state STR/GEO and
<300 kN> for Serviceability limit state. As the embankment will still be made, the sur-
charge does not change.
11. Check the option Use pile grid to replace current pile positions to replace the single pile
that was entered in the previous example.
12. Click the OK button to close the window. D-F OUNDATIONS generates a pile plan consisting
of 36 piles with the given properties.
13. Click the Top View Foundation node in the tree view to display a graphical representation
of the pile plan, as illustrated in Figure 10.3.

Figure 10.3: Top View Foundation window, Overview of the pile plan

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10.5 Starting the calculation

Now that all the information about the soil profiles and the pile plan has been entered, the
actual calculation can be started.

14. Switch to the Calculation window by selecting the corresponding node in the tree view.

Figure 10.4: Calculation window

15. Mark the Write intermediate results (Dutch) checkbox to make it possible to view the inter-
mediate results file.
16. Select Verification as the Calculation Type and Complete calculation under Calculation.
17. Check that the Pile type name is <Rect 250×250>.
18. Enter a depth of <-15 m> for CPT test level.
19. As dealing with storage facility, set the Rigidity of superstructure to Non-rigid. The input
should now correspond with the input given in file Tutorial-1.foi.
20. Click Start to begin the calculations. A report is automatically opened, containing the
calculation results.

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10.6 Evaluating the results

21. To see if the design meets the requirements of limit states STR, GEO and serviceability
limit state, scroll down to the part of the report shown in Figure 10.5.

Figure 10.5: Report window, Results of the Verification of Limit States STR, GEO, and
serviceability limit state (Tutorial-3a)

It can be seen that the design does not satisfy the requirements for limit state GEO and
serviceability limit state.

Note that this calculation was made for a non-rigid superstructure. This is the default choice,
which represents a worst case situation.

22. Click Save As in the File menu and save the project as <Tutorial-3b>.
23. Click Save to close the window.
24. To verify if the design is OK for a rigid superstructure, return to the Calculation window.
25. Select Rigid under Rigidity of superstructure.
26. Click Start again.

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Figure 10.6: Calculation window, Selecting Rigid for the Rigidity of superstructure

Note: There are two alternative ways to let the design meet the demands, namely by choos-
ing a pile type that has a larger diameter, or by using more piles. However, both decisions
would increase the cost of the design. If the assumption of a rigid superstructure is legitimate,
according to NEN 9997-1+C2:2017 art. 7.6.1.1(c), this option is preferred.

From the report that results (Figure 10.7) it can be concluded that the requirements now meet
for all limits states.

Figure 10.7: Report window, Results of the Verification of Limit States STR, GEO, and
serviceability limit state (Tutorial-3b)

10.7 Conclusion
This tutorial has shown how to define and verify a grid of piles. It has been seen that the
rigidity of the superstructure can affect whether the design meets the requirements of the limit
states.

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11 Tutorial 4: Pipeline Duct on Bearing Piles
In this tutorial the bearing piles foundation for a pipeline duct is designed and verified in
accordance with EC7-NL (NEN 9997-1+C2:2017).

The objectives of this exercise are:

⋄ To learn the steps needed for a complete design and verification for a foundation con-
sisting of bearing piles.
⋄ To gain perception of the consequences of options chosen prior to calculation.
⋄ To determine the needed pile tip levels for the foundation to be constructed.

This tutorial is presented in the files Tutorial-4a.foi to Tutorial-4f.foi.

11.1 Introduction to the case

Figure 11.1: A pipeline duct (Tutorial 4)

This tutorial considers the design and verification of a pipeline duct supported on a bearing
piles foundation. Due to fluids flowing through the pipe, the weight of the construction and
wind loads, there will be horizontal forces, vertical forces and moments acting on the piles.
In this tutorial, it is assumed that the vertical loads on the piles are representative for the
construction, and that the effects of horizontal forces and moments on the foundation are
negligible. Two supports will be considered for the pipeline duct, each consisting of four piles
underneath a concrete slab. The required design loads per pile are set by the constructor
of the duct at 750 kN for limit state STR/GEO and 500 kN for serviceability limit state (more
information on the limit states can be found in section 16.2).

In order to collect enough information about the soil profile of the subsoil, two cone penetra-
tion tests have been done, one for each support. The depth of the CPT is to approximately
reference level -24 m, while the surface level is at reference level +1.3 m. One of the cone
penetration tests is shown in Figure 11.2 below.

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Figure 11.2: CPT 01 at the site where the pipeline duct is to be constructed (Tutorial 4)

11.2 Project input

1. Set up a new project (the method is described in Tutorial 1 in section 8.2).
2. Name the project <Tutorial-4a>.
3. Enter <Tutorial 4 for D-F OUNDATIONS > as Title 1 and <Pipeline Duct on Bearing Piles>
as Title 2 in the Description window.
4. Make sure that the Project Model is set to be Bearing Piles (EC7-NL) in the Model window.
5. Import the cone penetration tests (that are shipped with D-F OUNDATIONS), named Tutorial-
4 CPT 01.gef and Tutorial-4 CPT 02.gef.
6. Convert both CPTs to soil profiles (as described in section 8.4), using the <NEN rule>
with a minimum layer thickness of <0.05 m>. Because of the compressibility of the soils
the expected settlements of the surface exceed 10 cm, so negative skin friction has to
be taken in account. Therefore, it should be specified to what depth negative skin friction
occurs. Inspect both profiles, either in the graph or the in the table. It appears that negative
skin friction occurs above -11.6 m for profile 1 and above -10.2 m for profile 2. Below these
levels, the soils are too firm for negative skin friction to develop.
7. Fill in these values on the Additional Data tab for each profile, both for Top of positive skin
friction and Bottom of negative skin friction. Also specify the Phreatic level at <0.5 m>.
8. Define two pile types (as described in section 8.5) which are both prefabricated square
concrete piles, one with a width of 400 mm and one with a width of 500 mm. Do not select

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Use Pre 2016.

11.3 Preliminary Design

The first stage in the design process is to determine the minimum pile tip level needed for limit
state EQU. As seen in the previous tutorials, this requires a preliminary design using just a
single pile.

9. Enter a single pile as described in section 8.6 and fill in a surcharge of <9 kN/m2 >. This
surcharge corresponds to an embankment of sand with a height of 0.5 m. The X and Y
co-ordinates of the pile are both set to <0 m>. Leave the Pile head level at <1.3 m>.
10. Click the Calculation node and select Rigid for Rigidity of superstructure.

Note: Since each support consists of one relatively small concrete slab with four piles, one
support can be seen as a rigid construction. However the pipeline duct as a complete structure
is a non-rigid structure. For a preliminary design only a single pile is considered.

11. Select Preliminary Design and Pile tip levels and net bearing capacity,specify a trajectory
from reference level <-10 m> to <-20 m> with an interval of <0.25 m> and enter a Net
bearing capacity of <750 kN>.
12. Mark the Write intermediate results (Dutch) checkbox.

Note: The calculations should be performed separately for each CPT, otherwise the default
value for the ξ3 and ξ4 factors will be 1.32 (two CPTs for rigid superstructure) instead of 1.39
(one CPT for rigid superstructure). The latter ξ3 and ξ4 factors are valid for just one rigid
support which is the case, so select just one CPT for each calculation.

13. Highlight CPT 2 under Selected Profiles and click the button to transfer it out of the
Selected Profiles window and into the Available Profiles window (Figure 11.3). The calcu-
lation will now only be performed for CPT 1.

Figure 11.3: Calculation window, Selection of CPT 1 for calculation (Tutorial 4a)

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14. Click Start to begin the calculation and read the results from the tables from the Design
Results window that opens (Figure 11.4).

Figure 11.4: Design Results window (Tutorial 4a)

15. Click Save As in the File menu and save the project as <Tutorial-4b>.
16. Repeat the calculation for CPT 2, using the and buttons to move the CPTs between
the Selected CPTs and Available CPTs windows.
17. Read the results from the tables from the Design Results window that opens (Figure 11.5).

Figure 11.5: Design Results window (Tutorial 4b)

An overview of the required pile tip levels is given in Table 11.1.

Table 11.1: Pile tip levels resulting from the preliminary design

Pile type CPT 1 CPT 2

Prefab square 400 mm -14.25 m -14.0 m
Prefab square 500 mm -13.5 m -13.0 m

11.4 Verification of the design

It is now necessary to verify if the designed construction is OK for limit states STR, GEO and
serviceability limit state for the calculated pile tip levels.

The pile plan needs to be entered. The co-ordinates of the piles are as follows:

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⋄ for support 1: (1, 2), (1, 4), (3, 2), (3, 4);
⋄ for support 2: (9, 9), (9, 11), (11, 9), (11, 11).

The simplest way to enter these piles is to use the Generate Pile Grid option twice.

18. Click Save As in the File menu and save the project as <Tutorial-4c>.
19. First enter the piles for support 1. Start at the point (1, 2) with a Centre to centre distance
of <2 m> in both directions and with 2 piles in each direction. Keep the pile head at
<1.3 m> and the Surcharge load at <9 kN/m2 >. Set the design loads working on each
pile of <750 kN> (Limit state STR/GEO) and <500 kN> (Serviceability limiting state).
The option Use pile grid to replace current pile positions should be selected.
20. Follow the same procedure to enter the piles for support 2, this time starting at (9, 9). The
loads are the same as for support 1. This time the option Use pile grid to replace current
pile positions should be deselected to avoid overwriting the input for support 1. Figure 11.6
shows the input pile plan as displayed in the Top View Foundation window.

Figure 11.6: Top View Foundation window, Pile plan of the two supports

All the information required to verify if the construction meets the requirements for limit state
GEO and serviceability limit state has now been entered.

21. Perform a Verification Design calculation for the pipeline construction, selecting both CPTs
and pile type Rect 500×500.
22. Change the End of the Trajectory to <-15 m> as now it is known that deeper levels are
not of interest. Set CPT test level to <-15 m>.
23. As about to perform a calculation based on the entire pile plan for the entire construction,
keep in mind that the construction is only partly rigid (each footing on its own). So make
sure that the correct ξ3 and ξ4 factors will be used. Override ξ3 and ξ4 factors by selecting
its box and fill in the proper value (for 1 CPT and rigid superstructure): Factor ξ3 and
ξ4 = 1.26. If the determination of ξ3 and ξ4 is done by the program with rigid selected, it
would be based on 2 CPTs resulting in a value of 1.20 (ξ3 ) and 0.96 (ξ4 ).

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Figure 11.7: Calculation window, Selection of CPTs and pile type for Verification, Design
calculation(Tutorial 4c)

24. Click Start to perform the calculation.

25. In the Design Results window that opens (Figure 11.8), select the Text tab. From the table
that is shown, it can be seen that limits state GEO and serviceability limit state (SLS) are
passed for levels of -13.50 m and deeper for the representative CPT of both CPTs.

Figure 11.8: Design Results window, Text tab (Tutorial 4c)

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11.5 Maximum negative skin friction

D-F OUNDATIONS can be used to calculate the maximum negative skin friction load for piles, in
this case prefab concrete square piles with a width of 500 mm and a pile tip level of -13.5 m.
Choosing -13.5 m ensures that the full negative skin friction zone is taken into account, hence
providing the maximum value.

26. Click Save As in the File menu and save the project as <Tutorial-4d>.
27. Fill in a Pile tip level of <-13.5 m> in the Additional Data tab for both soil profiles.
28. In the Calculation window, perform a Verification – Complete calculation (Figure 11.9).

Figure 11.9: Calculation window, Selection of CPTs and pile type (Tutorial 4d)

29. When the calculation has finished, click the Intermediate node in the tree view.

As can be seen in Figure 11.10, the Intermediate Results are only available in Dutch at
present. The value of maximum negative skin friction can be found in the column Fs;nk;k for
limit state GEO and in column Fs;nk;d for serviceability limit state for the two CPTs (Sond. Nr.)
and the eight piles (Paal Nr. 1 to 8). Scroll through the results and search for the block of data
shown in Figure 11.10.

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Figure 11.10: Intermediate Results window (Tutorial 4d)

From these results, it can be concluded that the maximum negative skin friction value (Fs;nk;d )
in limit state GEO is 465 kN for CPT 1 (Sond. Nr. 1) and 330 kN for CPT 2 (Sond. Nr. 2).

Now, perform the calculation again without looking at pile group effect. To do so:

30. Click Save As in the File menu and save the project as <Tutorial-4e>.
31. Deselect the option Use pile group. This option applies to the calculation of negative skin
frictions. If it is not selected, the calculation for negative skin friction will be performed for
a single pile instead of a pile group, therefore using a value of 1.0 instead of 1.2 for γf ;nk
in limit state GEO, according to standard NEN 9997-1+C2:2017 art. 7.3.2.2.
32. After the calculation has finished, open the Intermediate Results window again.

Figure 11.11: Intermediate Results window (Tutorial 4e)

From these results, it can be concluded that the maximum value for negative skin friction in
limit state EQU has decreased to 425 kN for CPT 1 and 297 kN for CPT 2. As the EC7-NL
(NEN 9997-1+C2:2017) allows for both methods, it is also allowed to use the best results (in
this case, the ones without the pile group).

Note: The negative skin friction (Dutch: Fs;nk ; English: Fs;nsf ) for a single pile is also cal-
culated when performing preliminary design calculations. After performing Indication Bearing
capacity, the values can be plotted by selecting Fs;nsf as Force in the Design Results window.

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11.6 Using continuous flight auger piles

It has come to light that there is some vibration sensitive equipment present in the vicinity of
the pipeline duct. Therefore it is advisable to change the pile type to continuous flight auger
piles with a diameter of 400 mm.

33. Fill in this type of pile in the Pile Types window as shown in Figure 11.12 (only the pile type,
shape and diameter need to be set).

Figure 11.12: Foundation – Pile Types window, Adding the continuous flight auger pile
(Tutorial 4f)

The pile plan has already been defined, so the Verification – Design calculation can be per-
formed almost right away. Follow the steps below to determine the pile tip level for limit states
EQU, GEO, and serviceability limit state, calculating for each cone penetration test separately
so that the correct ξ3 and ξ4 factors are applied automatically.

34. Click Save As in the File menu and save the project as <Tutorial-4f>.
35. In the Calculation window, select Verification – Design calculation.
36. Make sure the option Use pile group is deselected, select <Round 400> as the Pile type
name, set the End of the Trajectory to <-20 m> and check that both CPTs are selected.
37. Click Start to perform the calculation.
38. Select the Text tab in the Design Results window.

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Figure 11.13: Design Results window, Text tab (Tutorial 4f)

It can be seen that from pile tip level -19.00 m downwards, all limit states are met. Therefore,
the pile tip level must be reference level -19.00 m or deeper.

11.7 Conclusion
This tutorial has shown how to construct a complete design for a simple foundation on bearing
piles in accordance with EC7-NL (NEN 9997-1+C2:2017). It has also shown that the options
chosen in the Calculation window can affect default values of several parameters. Finally, it
shows the effect of granularity of the soil types on the positive skin friction and thus the overall
bearing capacity.

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12 Tutorial 5: Preliminary Design of Tension Piles for a Parking
Garage
This tutorial considers the design of the foundations for an underground parking garage in
accordance with EC7-NL (NEN 9997-1+C2:2017). Tension piles are needed to counter the
up thrust caused by the floor of the garage being located below the groundwater level.

The objectives of this tutorial are:

⋄ To learn the steps needed for a complete design and verification of a foundation con-
sisting of tension piles.
⋄ To learn how to create a soil profile manually instead by automatic interpretation of CPT
data.
⋄ To learn how to reduce the cone resistance due to excavation.

This tutorial is presented in the file Tutorial-5.foi.

12.1 Introduction to the case

This tutorial describes the design of a foundation of a parking garage to be constructed un-
derground. The floor of the garage will be located about 4 m below phreatic level, resulting in
upward pressure acting on the foundation. This upward pressure is compensated partially by
the walls of the garage, but this compensation is not sufficient. Tension piles are needed for a
balanced situation.

Figure 12.1: Design of a foundation of a parking garage (Tutorial 5)

The compensation of the walls is smallest in the center of the garage. Therefore, the center
pile of the foundation will bear the greatest tension loads and is most of interest. Soil in-
vestigation, consisting of one CPT, was carried out near to the planned parking garage eight
years ago. The file data is available in an old format which was used for the predecessor
of D-F OUNDATIONS, NENGEO. D-F OUNDATIONS is able to import old CPT file formats such as
son-files, so this will not be a problem. More recently, a boring has been carried out at the
future location of the garage, to obtain additional data for the subsurface.

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Table 12.1: Characteristic values of soil parameters based on boring

Top of soil layer to reference level Material γdry γwet

[m] [kN/m3 ] [kN/m3 ]
-0.69 Loam 20.0 20.0
-6 Soft clay 17.0 17.0
-14 Peat 12.5 12.5
-15 Sand, clean 18.0 20.0

12.2 Entering the project data

1. Create a new project by selecting New in the File menu.
2. In the Project Properties – Description window displayed, enter the text <Tutorial 5 for
D-F OUNDATIONS > for Title 1 and <Parking Garage on Tension Piles> for Title 2.
3. Save the project as <Tutorial-5> in the Save As window from the File menu.
4. Select Model from the Project menu and select the Tension Piles (EC7-NL) option in the
Model window that opens.

Figure 12.2: Model window

5. Click OK to close the window.

12.2.1 Soil profile

6. To import the CPT data, click the Soil - Profiles node in the tree view.
7. Select Tutorial-5 CPT 01.son to import the cone penetration test that was performed on
the location where the parking garage is to be constructed.

The soil profile derived from the information of the boring is given in Table 12.1. The inter-
preted soil profile based on the boring shows a somewhat different outline of the subsurface
than the CPT does.

After comparing the CPT and the boring data it can be concluded that the CPT shows much
more sand layers between ground level and the top of the deep Pleistocene sand layer. The
tension bearing capacity of a pile in soft soils is much lower than the tension bearing capacity
of a pile in sand layers, which has a consequence for the total bearing capacity for tension
load of the subsoil. The bearing capacity for tension derived from the CPT data will be higher
than the bearing capacity for tension based on a soil profile derived from the boring.

Since the boring has been done at the site of the future parking garage recently, whilst the
nearby CPT was performed a while ago, it is believed that the information of the boring is more
accurate for the compilation of the soil profile needed for the calculations. However, according

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to NEN 9997-1+C2:2017, CPT data is needed for tension pile calculations. A way to get
partially round this is to create a soil profile manually, starting from the CPT and modifying
the interpretation according to the data from the boring. Naturally in a later stage additional
soil investigation needs to be done to check whether the soil profile used really resembles the
situation at site.

The CPT data has already been imported, so the soil profile can be built up by following these
steps:

8. Select the <NEN rule> as CPT Rule and fill in a large value for the Min. layer thickness,
say <10 m>, and click the Transform the interpreted CPT into a profile button to copy
the interpretation to a new profile. The profile is now reduced to only a few layers of two
different materials, as shown in Figure 12.3.

Figure 12.3: Soil – Profiles window using NEN rule and a minimum layer thickness of
10 m

9. In the table, select Undetermined from the drop down menu for the Material of each layer.
Now the only information still retained from the CPT is its surface level. Now the soil
parameters, based on the information of the boring, can be added. Use will be made of
the standard table NEN 9997-1+C2:2017 that is provided with D-F OUNDATIONS when filling
in the material data.
10. Switch to the Soil – Materials window.
11. Delete all the existing materials by clicking the Delete row button.

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12. Click the Add from NEN 9997-1 button to add a material.
13. In the NEN 9997-1 Table 2.b window that opens, select the materials that come closest to
the data retrieved from the boring analysis given in Table 12.1, namely:
⋄ Loam, slightly sandy, moderate
⋄ Clay, clean, moderate
⋄ Peat, moderate preloaded, moderate
⋄ Sand, clean, moderate
14. Manually correct the dry and wet unit weight for the Peat, changing them both to <12.5>.
15. To make sure the layers containing clay do not contribute to the tension force, set Apply
tension to False for the Clay.

Figure 12.4: Soil – Materials window

16. Switch to the Soil – Profiles window and compose the soil layer manually, by adding a row,
filling in the correct top levels and selecting the right material for each layer from the drop
down list available under the material column (see Figure 12.5).

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Figure 12.5: Soil – Profiles window, selection of materials for the profile

Note: As an alternative to typing layer boundaries in the table, layers can be added graphi-
cally using the Add boundary button. Press this button and click anywhere in the graph; a
new layer is selected on that position. After enough layers have been added, press the Edit
button, select a layer boundary and drag it to the proper position. To change the material,
select the required one from the toolbox on the left side of the screen (beneath the tree view),
drag this material to the layer of choice and drop it onto the layer.

17. Switch to the Pore Pressure and OCR tab to check that all pore pressures are <0> and
that all OCR values are <1>. If the phreatic groundwater level and water pressure of the
first aquifer are different this can have an influence on the tension bearing capacity of the
piles. Excess pore pressures, which can be negative, with depth in that case can occur.
An OCR of 1 means that the soil is not over-consolidated. An over-consolidated soil has
been preloaded, either by an actual load on the surface or by other soil layers which have
consequently eroded.

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Figure 12.6: Soil – Profiles window, Pore Pressure and OCR tab

18. Switch to the Additional Data tab and fill in values of <-2 m> for the Phreatic level, <-
24 m> for the Pile tip level, and <-9 m>, one meter below the excavation level, for the
Top of tension zone.

Figure 12.7: Soil – Profiles window, Additional Data tab

12.2.2 Foundation
Now that the soil profile has been entered, the foundation itself can be inputted. The piles to
be used are driven concrete square piles with a width of 450 mm. The pile head level is set to
-6 m (= excavation depth), and the center to center distance of the piles is 2 m.

19. Select the Pile Types node in the tree view and enter the pile type as described above.
Note that all the default values are OK; only the base height and base length of <0.45 m>
need to be filled in.

Figure 12.8: Foundation – Pile Types window for a rectangular pile

20. Click on the Pile Properties node and generate a pile grid of 3×3 piles using a starting

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point of (0, 0) and a center to center distance of 2 m in both directions by clicking the
Generate Pile Grid button . The building pit will be excavated to a level of reference level
-6.0 m, so the Pile head level needs to be set to reference level -6.0 m (Figure 12.9).

Figure 12.9: Pile Grid Tension Piles (EC7-NL) window

21. Click OK. The tension forces acting on the center pile are the forces most of interest. Note
that the centre pile in the grid has been given the number 5.
22. Rename pile number 5 as <center> for easier identification later on.

Figure 12.10: Foundation – Pile Properties window showing input pile grid

12.2.3 Excavation
The next step is to define the excavation for the parking garage.

23. Click the Excavation node in the tree view to open the Excavation window.
24. Fill in an Excavation level of reference level <-6 m>, the level where the floor of the
parking garage will be situated.
25. For Reduction of cone resistance, select Begemann. For the requirements needed in
order to apply the Begemann method for reduction of the cone resistance see NEN 9997-
1+C2:2017 art. 7.6.3.3(c) (see also section 4.5).
26. For Distance edge pile to excavation boundary, fill in the (unrealistically large) value of

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<1000 m>. This to simulate a situation where the excavation is infinitely wide. This way,
the (positive) influence of the walls of the garage is minimized and a clear picture of the
bearing capacity of the middle pile can be obtained. Note that this is a safe approach.
27. Click Begemann again to display the correct results in the graph after changing the dis-
tance, as shown in Figure 12.11.

The diagram on the right hand side of the window shows the effect of the excavation, as inter-
preted using the Begemann method. It reduces the stresses in the soil, which is translated to
a reduction of the cone resistance of the CPT.

Figure 12.11: Excavation window with Begemann option selected

12.3 Calculation and results

28. Switch to the Calculation window and overrule the parameter for ξ3 with a value of <1.25>
and ξ4 with a value of <1.00>. Normally, the program would calculate with ξ3 of <1.39>
and ξ4 <1.39> (the proper value for a non rigid structure calculated based on one CPT).
However, the boring was used to determine the profile and it can be argued that this is a
more accurate profile than any profile based on the one CPT only. The superstructure is
non-rigid, the other default parameters and options are correct too.
29. Select Indication bearing capacity for the Calculation and define a Trajectory to Begin at
<-9 m> and End at <-24 m>, with an Interval of <0.25 m>.

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Figure 12.12: Calculation window for Tension Piles (EC7-NL) model

30. Start the calculation by clicking the Start button.

In the Design Results window that opens, four lines are plotted, two of which coincide. Each
of these lines shows the tension forces on a pile. Note that piles have been grouped. Due to
symmetry in the pile plan, the same forces apply to the four piles at the corners, the center
pile is unique, and the other four piles can be divided in two groups of two piles.

Figure 12.13: The simplified pile plan of the parking garage

31. In order to determine which of the pile groups contains the centre pile, select the Text tab.
The results are given separately for each pile group, and the names of the piles included
in each group are given. Scrolling down it can be seen that Pile group 4 is the group
containing the pile named <center> (Figure 12.14).

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Figure 12.14: Design Results (indicative ξ3 ) window, Text tab

32. Scroll down at the bottom of the window (Figure 12.15).

According to NEN 9997-1+C2:2017, art 7.6.3.3(8) (a), the tension force must be largely de-
rived from layers of sand. Cohesive layers percentages of 50% or more indicate that this is
not the case. Depths displayed in red in Figure 12.14 are the depths for which the cohesive
layers percentage is more than 50%. At a level of 24 m, the cohesive layers percentage is
35.09% which meets the requirement set by article 7.6.3.3(8)(a) in NEN 9997-1+C2:2017.

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Figure 12.15: Design Results (indicative ξ3 ) window, Text tab

33. Select the Chart tab. The line with the “+” markers indicates the results of the center pile
which are on interest. As can be seen in Figure 12.16, the tension forces are smallest for
this pile.

Figure 12.16: Design Results (indicative ξ3 ) window, Chart tab

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34. Select 4 under Pile group to display just the results for the center pile.

At a level of 24 m a tension force of 530 kN can be read. Looking it up in the Text tab, the
value actually equals 529.51 kN.

Note: This force does include the pile weight.

12.4 Conclusion
This tutorial has shown how to determine the bearing capacity for tension, for the middle pile
of a group, in accordance with EC7-NL (NEN 9997-1+C2:2017). It has also shown how to
construct a soil profile manually and how to overrule default parameters. Naturally in a later
stage additional soil investigation needs to be done to check whether the soil profile used
really resembles the situation at site.

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13 Tutorial 6: Farm with a Pond (Shallow Foundations)
This tutorial describes how to check the vertical bearing capacity of an existing shallow foun-
dation. Calculations are then performed to give an indication of whether this shallow founda-
tion still has enough bearing capacity and will remain stable under a new loading situation.

The objectives of this exercise are:

⋄ To learn how to use D-F OUNDATIONS to design a shallow foundation in accordance with
EC7-NL (NEN 9997-1+C2:2017).
⋄ To learn how to interpret the results of such a design.

This tutorial is presented in the file Tutorial-6.foi.

13.1 Introduction to the case

The owner of an old farm wishes to have a fishing pond near to his farmhouse. He wonders
if this could be realized without any damage to the building. This tutorial uses D-F OUNDATIONS
to ascertain whether the pond can be dug out near to the farmhouse without failure of the
foundations of the farmhouse.

FARM

Clay

1m

Sand
Strip foundation

Figure 13.1: Fishing pond near farmhouse (Tutorial 6)

The farm is founded on two strip footings (each underneath one of the two bearing building
walls of the farm) at reference level -1 m. The strip footings have a width of 600 mm and
a length of 10 m. The ground surface level near the farm lies at reference level 0 m. The
groundwater level is at reference level -0.5 m. For the purpose of this case, all calculations
must be performed for the strip at the side of the farm where the pond will be constructed.

The characteristic value of the pressure on the foundation strips is known to be 20 kN/m2 .
This force is applied at the center of strip footing. The partial load factor is given as 1.2
for limit states STR and GEO. The wind load acting on the building can be modeled as a
horizontal force with characteristic value of 0.5 kN/m1 applied at a reference level of 3 m. For
the evaluation of limit states STR and GEO, an extra partial load factor of 1.3 must be applied
for the horizontal load.

Results of a CPT are not available, however a boring done near to the farm is. The soil profile
given in Table 13.1 has been interpreted from this boring.

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Table 13.1: Soil profile near to the farmhouse

Number of Type of soil Top of layer relative

soil layer to reference level
1 Sand, clean, loose 0m
2 Clay, clean, weak -3 m
3 Peat, not prel, weak -4 m
4 Clay, clean, moderate -7 m
5 Sand, clean, moderate -16 m

13.2 Entering the project data

For this tutorial, a new file has to be created together with a new ‘empty’ profile as no CPT is
available:

1. Create a new project by selecting New in the File menu.

2. Save it as <Tutorial-6.foi>.
3. In the Project Properties – Description window displayed, enter the text <Tutorial 6 for
D-F OUNDATIONS > for Title 1 and <Farm with a pond (Shallow foundations)> for Title 2.
4. Select Model from the Project menu to change the model to Shallow Foundations.
5. At the Warning pop-up that follows (see Figure 13.2) choose "Yes" to ensure the use of the
proper values for the soil parameters.

Figure 13.2: Soil parameters, changing model warning window

6. Select the Profiles node and cancel the import dialog that pops up.
7. Select New in the Soil – Profiles window. This will generate an empty profile starting at
0 m, ending at -20 m and containing Undetermined as material. Edit this profile (see
Figure 13.3) using the values given in Table 13.1.

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Figure 13.3: Soil – Profiles window, Layers tab

8. Switch to the Additional Data tab. Here the Phreatic level should be set at <-0.5 m> and
the Placement depth of the foundation element at <-1 m>. Specifying the Concentration
value according to Fröhlich as 3 means the stress distribution model described by Boussi-
nesq will be followed. If a value of 4 is specified then an increasing stiffness with depth for
the soil layers can be simulated. This tutorial uses the default value of <3>.

Figure 13.4: Soil – Profiles window, Additional Data tab for Shallow Foundations model

9. Click on the Foundation – Types node in the tree view. A new foundation type is auto-
matically created. Define a Rectangular shaped element with a Width of <0.6> m and a
Length of <10 m>. Set the Type to <Cast in place>.

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Figure 13.5: Foundation – Types window

10. Click on the Foundation – Loads node in the tree view. A new load is automatically created.

The first objective is to check the current vertical bearing capacity of the foundation of the old
farm, so the load entered should be the current load acting on the foundation. The character-
istic vertical design load is calculated from the data given in section 13.1, by multiplying the
area of the strip 0.6 m × 10.0 m = 6.0 m2 by the given pressure of 20 kN/m2 . This results
in a characteristic value for the load of (6.0 × 20.0) = 120 kN, which should be entered as
the Vertical Design load value for Serviceability limit state (for info on the limit states, see in
section 18.2).

To calculate the Vertical Design load value for Limit state STR/GEO, multiply this load by the
partial factor of 1.2, resulting in a load of 144 kN.

The horizontal wind load also needs to be applied in order to determine the vertical bearing
capacity. The horizontal load results in a moment, which in turn can be translated to an
eccentric vertical load at foundation level. According to NEN 9997-1+C2:2017 art. 6.5.2.2(b),
the surface area of the foundation needs to be reduced when an eccentric vertical load acts
on the foundation. This results in a (much) lower vertical bearing capacity. This reduction of
the surface area is performed automatically by D-F OUNDATIONS when a horizontal or eccentric
vertical load is input.

The characteristic value of the horizontal load is 0.5 kN/m. For a strip 10 m long this results
in a total horizontal load of 5 kN, which can be entered as the value of the Horizontal Design
load for Serviceability limit state. To calculate the value for Limit state STR/GEO, this load
must be multiplied in this case by the partial factor of 1.3, resulting in a load of 6.5 kN.

The horizontal load acts on reference level +3 m and the foundation level is at reference level
-1 m. The Initial eccentricity to foundation level (Eh) therefore equals 4 m for both limit state
STR/GEO and serviceability limit state.

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Figure 13.6: Foundation - Loads window

11. In the Foundation – Loads window, input all the load information as given above.
12. Open the Foundation Plan window and click on the first row, to input the foundation plan.
The foundation type, load and profile are automatically selected as shown in Figure 13.7.

Figure 13.7: Foundation Plan window

All information has been entered and is now ready for the first calculation.

13.3 Verification of the design

The existing situation can now be verified.

13. Switch to the Calculation window. The maximum allowed settlement and relative rotation
given in the Calculation window are according to NEN 9997-1+C2:2017 or are default
values of D-F OUNDATIONS.
14. Mark the Write intermediate results (Dutch) checkbox to be able to access to the interme-
diate results of the calculation.
15. Select Verification under Calculation and click Start.

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Figure 13.8: Calculation window with default deformation demands conform to EC7-NL
(NEN 9997-1+C2:2017)

After calculation is complete, the Report window opens. The results of the calculation are
given in the section “Shallow Foundations: Results of Verification” of the report.

As can be seen in Figure 13.9, the foundation meets all requirements in limit state EQU
(PASSED) except the tip over stability (FAILED).

Note: The only check that is done in D-F OUNDATIONS for the tip over stability is a check
whether or not the effective width and effective length of the foundation is smaller than respec-
tively 2/3 of the actual width and 2/3 of the actual length of the foundation. This is according
to NEN 9997-1+C2:2017 art. 6.5.4(1)P. If the effective width and effective length are smaller
than 2/3 of the actual width and 2/3 of the actual length the tip over stability is indicated as
FAILED in the report. Since the foundation has been stable for more than a few decades, the
tip over stability most probably is sufficient. Further calculations on tip over stability need to
be done in accordance to chapter 11 of NEN 9997-1+C2:2017 to verify this. The remainder of
this tutorial assumes that the tip over stability criterion is indeed met for the situation without
the pond.

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Figure 13.9: Report window, Results of the Verification of Limit State EQU

For Serviceability limit state, the settlements are sufficiently small in accordance with NEN 9997-
1+C2:2017 art. 2.4.9 and the foundation is indicated as PASSED (Figure 13.10).

Figure 13.10: Report window, Results of the Verification of Serviceability Limit State

For limit state STR/GEO (Figure 13.11), the criteria of a maximum settlement of 0.15 m is not
met when both 5% (suggested by Deltares) and 20% (as required by NEN 9997-1+C2:2017)
values are used.

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Figure 13.11: Report window, Results of the Verification of Limit State STR/GEO

Calculations for settlement, (NEN 9997-1+C2:2017 art. 6.6.2) are based on increase of ver-
tical effective stresses due to loads on ground level. Since the farm has been built a few
decades before with hardly any settlement since, it is concluded that the settlement is suffi-
ciently small in both limit state STR/GEO and serviceability limit state.

13.4 Influence of the fishing pond

Since the fishing pond will be constructed near to the farmhouse, the total stability of the
foundation in combination with the slope of the pond needs to be checked as well.

The pond is planned at a distance of 1 m from the foundation strip, with a maximum depth of
1.5 m. The slope of the edge of the pond has a ratio of 1:3. In D-F OUNDATIONS it is assumed
that the pond extends infinitely beyond the slope.

16. Click the Slopes node in the tree view to open the input window where the parameters that
define the pond slope can be entered.
17. Click in the table to create a new slope, and give it a descriptive name such as <Pond
Slope>.
18. Enter the Slope height of <1.5 m>, the Slope length of <4.5 m> (derived from the ratio
1:3) and the Berm width of <1.2 m>.

Figure 13.12: Soil – Slopes window

19. Switch to the Foundation Plan window and add a second row by clicking the Add row
button. Then select the <Pond Slope> in the last column of the table (Figure 13.13).

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Figure 13.13: Foundation Plan window

Note: The position (X and Y coordinates) do not need to be changed. When calculating
alternatives (i.e. different possible solutions for one problem), all elements may be located at
the same position in the foundation plan as the alternatives are all calculated by themselves.
Only when performing a calculation of a real foundation plan (i.e. multiple elements in one
plan which interact with each other), it is needed to physically separate the elements by giving
them their own positions. In that case, the Use interaction model in the Calculation window
also needs to be enabled.

20. Click the Calculation node to open the Calculation window and click Start.

Upon completion of the calculation the report is displayed. According to Figure 13.14, the
bearing capacity Rd is the same (338.10 kN) for both cases (with and without the presence
of the slope) which means that the slope has no influence as it is too far away from the
foundation.

Figure 13.14: Report window, Results for Limit State EQU with and without the pond

In order to see the influence of the pond slope on the foundation, the distance between the
slope and the shallow foundation (called B in Figure 13.12) must be reduced:

21. Click the Slopes node in the tree view to open the Soil – Slopes window.
22. Add a second slope in the table, and give it a descriptive name such as <Pond Slope
near>.
23. Enter the Slope height of <1.5 m>, the Slope length of <4.5 m> (derived from the ratio
1:3) and the Berm width reduced to <0.7 m>.
24. Switch to the Foundation Plan window and add a third row by clicking the Add row
button. Then select the <Pond Slope near> in the last column of the table.
25. Click the Calculation node to open the Calculation window and click Start.

Note that the bearing capacity Fr;v;d has decreased from 338.10 kN to 174.34 kN. This re-
duction of the bearing capacity is in accordance with NEN 9997-1+C2:2017 art. 6.5.2.2(p)
due to the presence of the slope. However the bearing capacity is still sufficient for the new
situation – the verification has still been PASSED.

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Figure 13.15: Report window, Results for Limit State EQU without pond and with two
different ponds

In paragraph 3.1.4 of this report it can be seen that construction of the pond may lead to
problems with the tip over stability. This was already the case for the situation without the
pond. But now, further calculations on tip over stability need to be done in accordance to
chapter 11 of NEN 9997-1+C2:2017 to determine whether the situation with the fishing pond
is stable for tipping over or not.

13.5 Conclusion
This tutorial has shown how to determine the vertical bearing capacity when vertical and hor-
izontal loads and moments work on a shallow foundation. It has been noted that if tip over
(or total stability) is said to fail this means that failure should be verified by more extended
additional calculation in accordance with NEN 9997-1+C2:2017 (EC7-NL). These further sta-
bility calculations are not integrated in D-F OUNDATIONS. They would require a lot more input
by the user, an additional model and extra output. In fact, these further stability calculations
require a program in its own right: such a program is available at Deltares Systems under the
name D-G EO S TABILITY (formerly known as MStab). Furthermore it can be concluded that the
vertical bearing capacity of a shallow foundation will decrease when the foundation is near a
slope.

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14 Tutorial 7: Obsolete (Previously: Design of Bearing Piles using
the Belgian method)
This tutorial is no longer available, since the Bearing Piles EC7-B model was removed in
release 22.1.

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 15 Tutorial 8: Verification of Tension Piles for a Parking Garage
A preliminary design step can only be used in order to obtain a first impression of the bearing
capacity with depth for a single pile foundation. In this tutorial D-F OUNDATIONS will be used to
verify the design from the tutorial 5 to see if it is actually correct.

The objectives of this tutorial are:

⋄ To verify the preliminary design from Tutorial 5 (chapter 12).

This tutorial is presented in the file Tutorial-8.foi.

15.1 Introduction to the case

In Tutorial 5, a preliminary design for the foundation of a parking garage was made. With this
tutorial the bearing capacity for tension, of the center of the pile group, was determined.

Knowing the pile plan and all details about the building, the required design loads per pile
are set, by the constructor of the building, at 370 kN for limit state STR/GEO and 300 kN for
serviceability limit state.

15.2 Preparing a new project

1. Click Open from the File menu and select the project Tutorial-5.
2. Select Save As in the File menu and save the project as <Tutorial-8> before continuing
this tutorial.
3. In the Project Properties – Description window, change Title 1 and Title 2 to respectively
<Tutorial 8 for D-F OUNDATIONS > and <Verification of Tension Piles for a Garage>.

15.3 Entering the project data

15.3.1 Soil Profile

Although, one CPT profile is inherited from Tutorial-5 to complete the Verification calculation
acording to the NEN 9997-1+C2:2017 code a minimum of two CPT’s are required. Thus, a
second CPT will be added to the calculation.

4. To import the CPT data, click Soil-Profiles node in the tree view and then click .
5. Select Tutorial-8-CPT-02.gef.
6. Select the <NEN rule> as CPT Rule, fill in <1 m> for the Min. layer thickness and click
the Transform the interpreted CPT into a profile button to copy the interpretation to a
new profile.

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Figure 15.1: Soil Profile window, Layers tab for CPT 02 after interpretation

In Figure 15.1 the top levels and materials for CPT 02 are shown. The layers in this case will
consist of the same materials as CPT 01.

7. Change the soil materials according to Figure 15.2.

8. In the Additional Data tab, set the Phreatic level at <-0.69 m>, the Pile tip level at <-
24 m> and the Top of tension zone to <-9 m>.

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Figure 15.2: Soil Profile window, Layers tab for CPT 02 after modification

15.3.2 Pile Properties

To perform a Verification calculation, the Limit states need to be defined for each pile. To do
that the following steps need to be followed.

9. In the tree-view select Pile Properties.

10. For all the piles set the Limit state EQU/STR/GEO to <370 kN> and the Serviceability
Limit state to <300 kN>.

15.4 Starting the calculation

Now that all the information about the soil profiles and the pile plan has been entered, the
actual calculation can be started.

11. Switch to the Calculation window by selecting the corresponding node in the tree view.
12. Select Verification as the Calculation Type.
13. In Overrule parameters, uncheck the values ξ3 and ξ4 .
14. Highlight CPT 02 under Available Profiles and click the button to transfer it in the Se-
lected Profiles. The calculation will be performed for both CPTs.
15. Check that the Pile type name is <Rect 450×450>.
16. Enter a depth of <-10 m> for CPT test level.
17. As dealing with storage facility, set the Rigidity of superstructure to Non-rigid.
18. Click Start to begin the calculations. A report is automatically opened, containing the
calculation results.

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Figure 15.3: Calculation window

15.5 Evaluating the results

19. To see if the design meets the requirements of limit states STR, GEO and serviceability
limit state, scroll down to the part of the report shown in Figure 15.4.

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Figure 15.4: Report window, Results of the Verification of Limit States EQU, STR/GEO
and serviceability limit state

It can be seen that the design satisfies the requirements for both limit states.

15.6 Conclusion
This tutorial has shown how to verify the preliminary design of a foundation consisting of
tension piles.

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 16 Bearing Piles model (EC7-NL)

16.1 Area of application

The bearing piles (EC7-NL) model is used to design foundations on piles according to the
Netherlands Eurocode 7 which has been implemented in NEN 9997-1+C2:2017 (NEN, 2017),
and/or to verify them on the basis of this standard.

The model can only be used to verify and design pile foundations classified in Geotechnical
Category 2 (GC2), which are subject to static or quasi-static loads that cause compressive
forces in the piles, provided that the calculation of pile forces and distortions is based on cone
penetration tests (CPTs). Any rising of (tension) piles and possible horizontal displacement of
piles and/or soil have not been incorporated into this model.

It should be stated explicitly that the model does not support raking piles. This is because
loads affecting raking piles usually do not satisfy the conditions specified in the previous para-
graph.

16.2 Limit states

The Netherlands Eurocode 7 bases the validation of constructions on three limit states. These
are:

⋄ Limit state STR is the ultimate limit state for checking forces: i.e. is the foundation
strong enough to support the building.
⋄ Limit state GEO is the ultimate limit state for checking distortions of the ground (settle-
ments and rotations): i.e. is the foundation solid enough to keep the building from being
torn, ruptured or dislocated.
⋄ Serviceability limit state is a serviceability limit state, only checking distortions at the
service load.

16.3 Calculation process

This outlines the way the verifications prescribed by the standards have been processed into
procedural step-by-step schematics suitable for use in a computer model:

⋄ (section 16.3.1) Verifying limit state STR

⋄ (section 16.3.2) Verifying limit state GEO and serviceability limit state

16.3.1 Verifying limit state STR

Verification of limit state STR is implemented in the following way in the bearing piles model.

First, for every CPT entered, the maximum bearing capacity for a single pile is determined as
the sum of the maximum bearing capacity of the pile tip and the maximum shaft friction force.
The following applies to the maximum shaft friction force:

⋄ Determining the maximum pile shaft friction deserves special attention. The execution
factor αs is not a fixed value here and is dependent on the soil type of the layer, as
well as on the depth of the relevant layer if the soil type is clay, loam or peat. For each
layer, therefore, the program calculates the generated pile shaft friction in that layer
after first defining the correct value of αs for the relevant layer. Aggregation of the pile
shaft friction calculated per layer in this way for the layers affected by pile shaft friction

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produces the eventual value of the maximum pile shaft friction.

⋄ Determining the circumference of the pile segment for which the maximum shaft friction
force is calculated as follows. If it involves a non-constant circumference, as is the case
with tapered wooden piles and piles with a reinforced tip, for example, the standard
(NEN 9997-1+C2:2017 art. 7.6.2.3 (c)) does not actually provide a solution. In that
case, the program calculates the mean circumference of the relevant pile segment.

Secondly, the maximum bearing capacity of the foundation is determined. Here, the number
of piles, the number of CPTs and the whether the structure may be considered as rigid or not
(NEN 9997-1+C2:2017 art. 7.6.1.1(c)) play a role.

⋄ In the case of a rigid structure, regardless of the number of CPTs, the program calcu-
lates the maximum bearing capacity of the foundation based on the average bearing
capacity of a single pile, multiplied by the total number of piles, since the foundation
element contains all of the piles.

⋄ In the case of a non-rigid structure, determination of the maximum bearing capacity of

the foundation depends on the number of CPTs. If there are more than three CPTs,
the definition is again based on the average bearing capacity of a single pile, whereas
if there are three CPTs or less, the minimum bearing capacity of a single pile is used.
In this case, the bearing capacity of a single pile is not multiplied by the total number of
piles because the foundation element consists of a single pile.

16.3.2 Verifying limit state GEO and serviceability limit state

Given the total number of piles and the total number of CPTs, verification of the limit state
GEO and serviceability limit state is implemented in the bearing piles model in the following
way.

Statistical variability is assumed with respect to the location of the CPTs. In other words, it is
taken for granted that each CPT in the given pile plan could be executed everywhere, since
a bad CPT can, in principle, occur at any location. In this way, dispersion in the CPTs as a
result of the heterogeneity of the subsoil is distributed over the entire foundation.

The worst forecast value is sought for the settlement in a non-rigid structure, while for a rigid
structure the average of the best estimator is defined.

An alternative given in the design code for determining the settlement in rigid buildings, based
on an advance average calculated from the values from the CPT, can only be applied under
very strict conditions (no negative skin friction, equivalent CPTs and soil profiles, no pile
groups etc.), and it is therefore not included in this model.

16.4 Geometric problems

When working through the standard regulations, the following geometric problems were dis-
covered:

⋄ NEN 9997-1+C2:2017, art. 3.2.3(e): Size and depth soil test

When checking the scope of the soil test, in the case of a random pile plan with several
CPTs, it was found that an analogous check on the prescribed area of influence for
each CPT of 25 × 25 m2 could lead to very slow response times because of the large
number of calculations that this entails. Consequently, an approach has been chosen

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that in some cases does not provide a solution and results in a warning in the output
file. This warning indicates that according to the somewhat restricted check performed
by the program, the scope of the soil test is not sufficient, but that the user may be able
to demonstrate the opposite manually. This manual confirmation should then be added
to the user’s results, of course.

⋄ NEN 9997-1+C2:2017 art. 7.6.4.2(k): Group of piles, settlement calculation

Although parameters A4;D , b1 and b2 specified in this article initially seem to be clear,
there is nonetheless a catch. If the cross-section of the pile base contains unequal
sides, the pile orientation is found to play a role. This pile orientation is not included
in the bearing piles model (to limit the required amount of input), so a conservative
approach has been incorporated into the program.

⋄ NEN 9997-1+C2:2017 art. 7.3.2.2(e): Pile group, negative skin friction calculation
Parameter A in this article has not been clearly defined. In particular, there is no defini-
tive way of determining A if there are irregular centre-to-centre distances between piles
within a pile group. For this reason, as high a value as possible is used for A (safe
approach). The users can replace this safe value with their own value after selecting
Area in the Overrule parameters sub-window of the Calculation window.

16.5 Problems in interpreting standards

First of all a short explanation on the vocabulary used in the description of the limit states is
in order.

Conform NEN 9997-1+C2:2017, D-F OUNDATIONS considers both the ultimate limit state (in
dutch Uiterste Grens Toestand, in short UGT ) as well as the serviceability limit state (in dutch
Bruikbaarheids Grens Toestand, in short BGT ). In past versions of the standard there were
2 situations to be considered for the ultimate limit state. The first situation, originally called
UGT type A, considered failure due to the exceeded bearing capacity. The second situation,
originally called UGT type B, considered failure due to exceeding distortion/displacement
limits. This approach is still in use for the current version of D-F OUNDATIONS.

However the names and descriptions of the limit states were altered during the lifespan of the
standards. At the moment the standards use:

⋄ EQU: the loss of equilibrium in either the construction or the supporting subsoil, un-
derstood as a rigid whole, in which the structural materials and the subsoil makes no
significant contribution to the resistance.

⋄ STR: the internal failure or exceptional deformation of the structure or of its components,
including, for example, foundations on steel, piles or basement walls, where the strength
of the construction materials make a significant contribution to the resistance.

⋄ GEO: the failure or exceptional deformation of the subsoil, where its strength makes a
significant contribution to the resistance.

Matched on the original types, this delivers:

⋄ UGT type A matches EQU

⋄ UGT type B matches STR/GEO
⋄ BGT just remained BGT

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We recognize the fact that D-F OUNDATIONS uses a slightly different definition of the UGT types
in order to make the matches work:

⋄ EQU: there is balance between load and resistance of the pile irrespective of defor-
mation. The resistance of the pile is determined via the cone penetration test values
or, in case of a shallow foundation, by a deterministic model. The properties of the
pile/foundation and of the soil are irrelevant (although the influence of pile/foundation
and soil are implicitly incorporated in the calculation model). It should be noted that the
standard itself states that this could apply to special cases (such as rock).

⋄ STR/GEO: loads on the pile/foundation and the resistance of it cause a deformation

which is passed on to the super structure. This includes properties of the pile/foundation
(shortening or lengthening) and properties of soil (interaction with and deformation un-
der the pile/foundation). In this test, for piles negative friction will be included as a load
on the pile. If the deformation becomes large, the bearing capacity and/or the limit value
for deformation may be exceeded. If the bearing capacity is exceeded, D-F OUNDATIONS
will indicate an infinite (very large) deformation.

Besides geometric and definition problems, the following problems also occurred when inter-
preting the standards:

⋄ NEN 9997-1+C2:2017 art. 3.2.3(e): Size and depth of soil test

With respect to the depth of the CPTs, this article specifies requirements with respect
to the pile tip level. However, because a pile plan can include several pile tip levels
(in the Bearing Piles (EC7-NL) model the user can define a pile tip level for each CPT
to this end), there is sometimes no such thing as a single pile tip level. The following
interpretation is used to solve this problem in the program: Every CPT must be at
least 5 m deeper than the pile tip level specified for that CPT. If 10 times the smallest
transverse measurement of the pile base is greater than 5 m, then for at least one CPT
the depth must also be greater than the corresponding pile tip level increased by 10
times that smallest transverse measurement. If these standard requirements are not
satisfied, a warning to this effect (referring the user to the article of the standard) is
included in the output file; if possible, calculation will still take place. It is only when
a specified depth exceeds the limits of the calculation model of the bearing capacity
(Koppejan) that no calculation will be executed.

⋄ NEN 9997-1+C2:2017 art. 1.5.2.128: Definition of a pile

It only makes sense to check the pile length on the basis of the definition of a pile in
this article if the phrase: "under ground level" is inserted after "Element for which the
length". The length of the pile above ground level actually has no effect on whether the
calculation model used in this standard may be applied or not.

⋄ NEN 9997-1+C2:2017 art. 7.6.4.2(k): Determination of Eea;gem

The determination of Eea;gem , the mean modulus of elasticity of the soil beneath the
level 4D under the pile point, is blurred. As opposed to a previous version of the norm
(NEN 6743:1991, art. 6.3.2), where it was determined from Eea;gem = 5 qc;z;gem , no
longer formula is given in NEN 9997-1+C2:2017. Deltares experts decided therefore
to use for Eea;gem henceforth 3 qc;z;gem , instead of 5 qc;z;gem , based on Table 2.b of
NEN 9997-1+C2:2017, where qc;z;gem is the mean value of the cone resistance over
the trajectory in the soil beneath the level 4D under the pile point to the level that is
b2 deeper, or, if the cone penetration test has not reached this level, to the actually
achieved penetration test level.

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⋄ NEN 9997-1+C2:2017 art. 7.6.2.3(e): Determining the maximum pile tip resistance
When determining qc;III;mean , the qc values for continuous flight auger piles should
be reduced to 2 MPa, unless it can be demonstrated, using CPTs performed after pile
installation at a maximum distance of 1 m from the pile, that this is not necessary.
Because it is not possible to program foresight, which is needed to process this pre-
condition automatically, it has been decided to allow the user to determine whether
the above-mentioned reduction should be applied or not prior to calculating continuous
flight auger piles. If the reduction does not have to be made, a message to this effect
is included in the output file because this assumption should be checked afterwards
on the basis of CPTs performed after pile installation. The requisite number of CPTs
performed after pile installation should be determined in consultation with the relevant
controlling body.

⋄ NEN 9997-1+C2:2017 art. 7.6.2.3(k): Requirements related to the CPT

If there is any reduction of the qc values in the case of an excavation, the method
′
used to determine the effective vertical tension (σv;z ) is not described in detail. Two
methods have therefore been built into the program to reduce the qc values in case of
an excavation. The Excavation window allows selection between these two methods
and a manual method.

⋄ NEN 9997-1+C2:2017, art. 7.6.4.2(j): Determining sel;d

This article contains two points of interpretation. Firstly, the description of the parameter
Ashaf t;d leaves no space for piles with a variable shaft diameter (tapered piles, piles
with reinforced base). To cater for this, Ashaf t;d has been interpreted as the average
diameter in D-F OUNDATIONS. Secondly, the formula supplied for Fmean;d does not work
if there is a gap between the positive and negative skin friction zone (in Figure 16.1, the
gap is presented as l2 ). This gap is filled by adding the following formula to the program
if this gap has actually been defined by the user:
Fgem;d = l1 × Fs;tot;d + l2 × (Fs;tot;d − Fs;nk;d ) +
0.5 × l3 × (Fs;tot;d − Fs;nk;d + Fr;point;d )
⋄ NEN 9997-1+C2:2017 art. 7.3.2.2(d): Determining the negative skin friction for
single pile
′
In this article, the formula specified for determining σv;i;k is only valid if the water level
is located in the first layer. Moreover, this formula is lacks the surcharge p0 . Therefore,
instead of the formula specified in this article, the program uses a more general proce-
dure for determining the effective vertical stresses, and any superimposed load is then
also taken into account.
Moreover, in this article, the formula for the determination of the characteristic neutral
earth pressure coefficient K0;j;k in layer j applies for OCR = 1. In case OCR is not
1, D-F OUNDATIONS uses the formula
√ of Jacky:
K0;j;k = (1 − sin φj;k ) × OCR.
⋄ NEN 9997-1+C2:2017 art. 7.3.2.2(e): Determining the negative skin friction for pile
group
′
With respect to making σm;v;i;k equal to p0;k it should be noted that this, of course, is
′
only valid for the 1st layer. For the other layers, the following relationship applies:σm;v;i;k =
′
σm;v;i−1;k

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Fs;tot;d
Fs;tot;d(=Fs;d+Fs;nk;d)

negative Fs;nk;d
l1 skin friction

l2 gap

positive
l3
skin friction

Fr;point;d Fr;point;d

Figure 16.1: Gap in skin friction zone

16.6 Units, dimensions and drawing agreements

It should be noted that the bearing piles model is based on a semi 3-dimensional approach.
On a flat plane, this is expressed in the pile and CPT plans specified. The third dimension
(the depth) is recorded in the CPTs and the corresponding soil profiles. A fully 3-D approach,
in which the piles can also be recorded to their full depth (raking piles), is not considered
desirable as this would allow pile configurations that are not covered by the calculation model
provided by the NEN.

The dimensional split between the flat plane on one hand and the depth on the other hand
also applies to the drawing agreements. In the flat plane, users are completely free to choose
their own axis system for the pile and CPT plans. With regard to the depth, all levels to
be entered must be recorded in relation to the reference level. This reference level can be
chosen freely as long as it is used consistently throughout a project. In the Netherlands, the
most common reference level would be the Amsterdam ordnance zero (i.e. NAP). Here, levels
above the reference level are considered as positive and levels below the reference level as
negative. Settlements, however, are considered as positive if they are pointing downward (see
Figure 16.2).

The units of the input and output parameters used in this model are displayed in the table
below. Although it has been attempted to keep the units for the parameters equal to the units
as they occur in the standards, in some cases this has been deviated from. In those cases,
insofar as the requisite accuracy allows this, a larger unit was chosen to somewhat limit the
length of the numbers to be entered and displayed. These deviant units are indicated in the
table with a * followed by the unit as mentioned in the standard.

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A
+8

NAP

pile settlement +

expected soil
settlement +

-24 A

Figure 16.2: Sign conventions

Table 16.1: Units of the input/output parameters

Description Symbol Unit

Pile tip level PTL m +/- NAP
Top level positive skin friction zone m +/- NAP
Bottom level negative skin friction zone m +/- NAP
Overconsolidation ratio OCR -
Cone resistance qc MPa
Expected soil settlement m
Ground level m +/- NAP
Ground water level m +/- NAP
Excavation level m +/- NAP
Bottom level of soil layer m +/- NAP
Volumetric weight of soil γ kN/m3
Volumetric weight of saturated soil γsat kN/m3
◦
Effective angle of internal friction φ’ (degrees)
Median (sand/gravel) (d50 ) mm
Reduction of cone resistance for excavation % (percentage)
Pile dimensions m
Pile factor for pile point αp -
Pile factor for shaft friction αs -
Young’s modulus for a pile Ep;mat;d kN/m2 (*N/m2 )
characteristic value of pile adhesion ai;k kN/m2 (*N/m2 )
Calculated value of load on pile in limit state Fs;d kN
Surcharge on soil next to pile p0 kN/m2
Pile head level m +/- NAP
characteristic value of maximum pile tip bearing capacity kN

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characteristic value of maximum shaft friction kN

characteristic value of maximum friction caused by negative kN
skin friction
Settlement s m
Relative rotation β m/m
Calculation value of the resulting maximum shaft tension in N/mm2
the pile.

Coordinates of piles and CPTs for determining the positions in the pile and CPT plans should
be specified in m.

16.7 Bearing Piles schematics

The requisite data for executing a (verification) calculation for a pile foundation according to the
standards can be divided into two groups. One group of data consists of information related
to the (foundation) construction (category superstructure, pile type, pile dimensions, pile plan,
etc.), while the other group involves data used to typify the subsoil (CPTs with corresponding
soil profiles, including height of groundwater level, expected ground level settlement, etc.).

When this data is displayed in a schematic (diagram), account should be taken of the relevant
requirements of the standard contained in articles 7.3.1 and 7.6.4.2 of NEN 9997-1+C2:2017.
In addition to these requirements, account should also be taken of the capabilities and limita-
tions of the bearing piles model. There are described in the following sections:

⋄ section 16.7.1 Problem boundaries

⋄ section 16.7.2 Variation in the level of the bearing layer
⋄ section 16.7.3 Skin friction zones
⋄ section 16.7.4 Non-rigid/Rigid superstructure
⋄ section 16.7.5 Combination of superimposed load/excavation
⋄ section 16.7.6 Merging sub-calculations

16.7.1 Problem boundaries

Because the model cannot be supplied with unlimited memory, the limits given in Table 16.2
apply to the maximum problem size.

Table 16.2: Limits applied to the maximum problem size

Maximum number of pile types 100

Maximum number of piles in pile plan 200
Maximum number of CPTs (i.e. soil profiles) 350
Maximum number of qc values per CPT 5000
Maximum number of layers per soil profile 100
Maximum number of iterations during design 151

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16.7.2 Variation in the level of the bearing layer

Although desirable, in practice, the use of a single pile tip level in a project is not usually
feasible. Variation in the level of the bearing layer for the executed CPTs forces designers to
use different pile tip levels.

The bearing piles model therefore allows users to define the required pile tip level for each
CPT. In this way, the user can cater for the above-mentioned variations in the bearing layer
level, at least as far as the Verification; Complete calculation option is concerned. In the
program’s Design options, the pile tip levels specified for each CPT are suppressed in favor
of the pile tip trajectory. In that case, the relevant pile tip level is retained as a starting point
for each calculation step, or for each pile tip level, for all CPTs.

It should also be noted that if the variations are significantly large, the project should be split
into sub-projects, and the variations should be kept within limits in each sub-project.

16.7.3 Skin friction zones

The necessary specifications are recorded in NEN 9997-1+C2:2017 for both the positive skin
friction zone (to determine Rs;cal;max;i;d ) and the negative skin friction zone (to determine
Fs;nk;d ).

For the positive skin friction zone, the bottom of that zone coincides with the pile tip level, and
for a prefabricated pile with a widened base, the top of that zone may never be above the
widening (NEN 9997-1+C2:2017 art. 7.6.2.3(c)). For the negative skin friction zone, the top
of this zone coincides with the ground level or excavation level.

Given the strong link between skin friction and the soil layer classification, the skin friction
zones are constructed of entire layers. This means that both the top of the positive skin
friction zone and the bottom of the negative skin friction zone should always coincide with a
layer boundary in the corresponding soil profile.

In order to satisfy these requirements in the bearing piles model, it was decided to define the
skin friction zones in the following way:

⋄ The bottom of the positive skin friction zone automatically coincides with the pile tip
level and therefore does not have to be entered.

⋄ The top of the positive skin friction zone is specified by the user as a level (in m) relative
to the reference level (usually NAP).

⋄ The top of the negative skin friction zone automatically coincides with the ground level
or excavation level and therefore does not have to be entered.

⋄ The bottom of the negative skin friction zone is specified by the user as a level (in m)
relative to the reference level (usually NAP).

Because neither the soil layer classification nor the pile type (in relation to a reinforced base)
needs to be known when the skin friction zones are being defined, the skin friction levels
cannot be checked at that moment. This is why the check is performed at the start of a
calculation.

If the top of the positive skin friction level does not meet the requirements (NEN 9997-
1+C2:2017 art. 7.6.2.3(c)) this level is automatically adjusted, if possible. The adjustment

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is performed in a safe way because the skin friction level is always placed on a lower level
than that specified by the user (see Figure 16.3).

1
2

2
; specified level
; final level

Figure 16.3: Skin friction levels

When skin friction levels do not coincide with layer boundaries (as they should), an extra layer
boundary, specific for the calculation, is added to the profile in order to be able to perform a
successful calculation. Only in the case of overlapping defined skin friction zones is calcula-
tion not possible, and an error message is displayed. If it does not involve a design calculation,
where automatic adjustment of skin friction levels is necessary, the adjustments are displayed
as a warning in the output file, and the original and adjusted levels are specified.

Use of prefabricated pile with reinforced tip

When a prefabricated pile with a reinforced tip is used and calculation of positive skin friction
is desirable, the maximum positive skin friction zone must be limited to the height of the
reinforcement in accordance with NEN 9997-1+C2:2017 art. 7.6.2.3(c), as already stated.
If the top of the positive skin friction zone is specified as being above the reinforcement, it
is automatically adjusted so that the maximum skin friction zone matches the height of the
reinforcement. Here, the top of the reinforcement does not have to be located at a layer
boundary. In this exceptional case, the program itself applies an individual layer boundary, if
necessary, in order to calculate the maximum positive skin friction.

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16.7.4 Non-rigid/rigid
One restriction when creating schematics is that for each calculation only (parts of) structures
that can be considered either as "completely rigid" or as "completely non-rigid" may be in-
cluded in a single schematic. If a project involves a structure that is partly "non-rigid" and
partly "rigid" (for example, a building with a rigid core), the user must execute at least two
calculations, one for the non-rigid part and one for the rigid part. Moreover, if the structure
consists of several different parts that can be considered as rigid, the user must execute a
calculation for each part. Figure 16.4 includes an example of division into sub-calculations.

1
2

Partial calculation 1: piles for rigid part of structure

Partial calculation 2: piles for non-rigid part of structure

Figure 16.4: Two different partial calculations required due to mixed rigidity of structure

For a definition of rigid/non-rigid, see NEN 9997-1+C2:2017 art. 7.6.1.1(c).

16.7.5 Combination of superimposed load/excavation

If a combination of superimposed (or surcharge) load and excavation occurs, the user en-
counters the following problem when calculating the bearing capacity. In accordance with the
standard, the bearing capacity is calculated for each CPT.

Reduction of qc values as a result of the excavation should therefore be executed for each
CPT. In the program, a superimposed load is recorded for each pile to give the user more
freedom when positioning the superimposed load, since there are generally more piles than
CPTs.

The consequence of this approach is that when there is a combination of superimposed load
(per pile) and excavation, the superimposed load for all piles being considered must be equal
to guarantee a correct bearing capacity calculation. The calculation model included in the
standard (NEN 9997-1+C2:2017) does not actually support calculation of the bearing capacity
per pile per CPT. As a result, no link can be made in the program between the superimposed
load to be entered per pile and the excavation. For the schematics, this means that if there is
an area in the problem definition with both an excavation and a superimposed load, it is again
necessary to split the problem into parts. This should be done in such a way that each part
meets one of the following requirements:

⋄ The relevant part contains neither excavations nor superimposed loads.

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⋄ The relevant part is typified by excavations but there are no superimposed loads.
⋄ The relevant part is typified by superimposed loads but there are no excavations.
⋄ The relevant part contains excavations and one identical superimposed load for all piles
in this part.

Figure 16.5 below is an example of a split.

1 2 3 4 5 6 excavation
area
1 2
8 9 10 11 12

13 14 15 16 17 18

3 4
20 21 22 23 24

19
25 26 27 28 29 30

Partial calculation 1: piles 1,7

Partial calculation 2: piles 2-6, 8-12
Partial calculation 3: piles 13, 19, 25
Partial calculation 4: piles 14-18, 20-24, 26-30

Figure 16.5: Splitting a problem into parts due to a combination of excavation and super
imposed loads

16.7.6 Merging sub-calculations

When splitting the problem into parts, the users themselves should calculate and verify the
rotation between those parts, based on the maximum settlements in limit state GEO and ser-
viceability limit state calculated for each part. The requisite centre-to-centre spacing between
rigid and non-rigid building components and between each of the rigid building components
should be carefully defined, if possible in consultation with the designer of the superstructure.

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17.1 Area of application

The tension piles model is used to design foundations on piles according to the Netherlands
Eurocode 7 standards which has been implemented in NEN 9997-1+C2:2017 test (NEN,
2017) and replaced CUR report 2001-4 “Design Rules for Tension Piles” (CUR, 2001).

The model can only be used to design pile foundations classified in Geotechnical Category 2
(GC2), which are subject to static or quasi-static loads that cause tension forces in the piles,
provided that the calculation of pile forces and distortions is based on cone penetration tests
(CPTs). Any rising of tension piles and possible horizontal displacement of piles and/or soil
have not been incorporated into this model.

It should be noted that in the NEN 9997-1+C2:2017 a number of requirements are given with
reference to the piles used in calculations with this model. These requirements are checked
by D-F OUNDATIONS but when one or more of the requirements are violated, instead of stopping
the usage of the model, D-F OUNDATIONS writes warnings to the Report file. The requirements
are:

⋄ minimum length of a pile is 7 m

⋄ maximum length of a pile is 50 m
⋄ the ratio between the pile length and pile diameter (or equivalent diameter when appro-
priate) is at least 13.5

It should be stated explicitly that the model does not support raking piles. Firstly, because
loads affecting raking piles usually do not satisfy the conditions specified in the previous para-
graphs; secondly, because a fully 3-dimensional approach is needed for the support of raking
piles, and this is not considered desirable given the limitations of the chosen hardware plat-
form. A fully 3-D approach would restrict the maximum problem size of this model.

17.2 Design of tension piles according to EC7-NL (NEN 9997-1+C2:2017)

For every CPT entered, the design value of the capacity in tension for each pile is determined.
The geometry of the piles is taken into account, as well as whether the structure can be con-
sidered as rigid or not, any variable loading of the pile, excavation influences and compaction
of the soil in the case of displacement piles.

Depending on the geometry, for each single pile or group of piles with equal parameters (pile
type, pile dimensions, distance to excavation, loading and geometry), the design value of the
capacity in tension is given.

The design option with fixed pile tip levels determines for each CPT the design value of the
bearing capacity for the pile tip level which is specified in the Additional Data tab of the Profiles
option for each CPT under the Soil node.

Using the design option Pile tip levels and net bearing capacity (section 5.6.2.3), the program
will determine, for each CPT, the highest pile tip level within the specified boundaries, for each
point where the design value of the capacity of the pile is greater than or equal to the “net
bearing capacity” value.

Note: For design option based on a trajectory, the determination whether a pile is situated in
clay only is always based on the deepest level of the trajectory. According to article 7.6.3.3(b)
of (NEN, 2017), when the tension force is largely derived from the layers of sand, the propor-

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tion of the cohesive layers (clay / silt) taken into account, must use a reduced factor αt (until
0.5 αt ). To determine whether this reduction is needed, the type of layer(s) next to the pile
must be reviewed. For calculations based on fixed pile tip levels, this is no problem. However
when a trajectory (or in fact a set of pile tip levels) is used, THE pile tip level required for the
determination, is not clear. So for this, D-F OUNDATIONS uses the deepest pile tip level from the
trajectory for the determination.

17.3 The Netherlands Eurocode 7 (EC7-NL)

The design of tension piles in D-F OUNDATIONS has adopted EC7-NL which is implemented
in NEN 9997-1+C2:2017 (NEN, 2017). This norm prescribes how to calculate the bearing
capacity of a pile as part of a group for a single CPT by adopting CUR report 2001-4. The
stiffness of the pile group construction or extra CPTs are only taken into account when deter-
mining the partial factors ξ3 and ξ4 .

Because constructions with tension piles are often used, for example in building pits, NEN 9997-
1+C2:2017 should be followed. In such cases (large groups of piles and several CPTs) special
attention should be given to determining the bearing capacity of the total construction of ten-
sion piles.

According to the Dutch standard NEN 9997-1+C2:2017, one CPT should be available every
25 m (maximum area 2625 m2 ) when no large variations occur. Otherwise, a maximum of
15 m (maximum area 2225 m2 ) is prescribed. When verifying the design of tension piles this
requirement should be checked. If the CPT area is larger than 2625 m2 and/or the distance
between 2 CPTs is larger than 25 m the results report will contain a warning (see NEN 9997-
1+C2:2017 art. 3.2.3(e)).

The D-F OUNDATIONS model for tension piles calculates not only the capacity for each pile at
each CPT and at chosen depths, but also provides the minimum, mean and maximum value
of the capacity in tension. According to NEN 9997-1+C2:2017, the bearing capacity of the
bearing piles of the foundation should be based on the average capacity of all CPTs and the
minimum capacity, whichever is less.

17.4 Verifying displacements of Tension Piles

As with Bearing Piles, the determination of the displacements of tension piles is calculated
according to NEN 9997-1+C2:2017, art. 7.6.4.

17.5 Calculating the bearing capacity of a tension pile

This section outlines the way the design and verification of tension piles is prescribed by
NEN 9997-1+C2:2017. The bearing capacity of a tension pile is basically considered to be
equal to the integration of the maximum shear stress along the pile shaft.

Based on NEN 9997-1+C2:2017, the following steps are taken into account:

⋄ section 17.5.1 Step 1: Determination of cone resistance

⋄ section 17.5.2 Step 2: Reduction of cone resistance due to excavation
⋄ section 17.5.3 Step 3: Safety factors: design values
⋄ section 17.5.4 Step 4: Effect of installation
⋄ section 17.5.5 Step 5: Reduction of stresses due to tension forces in pile groups
⋄ section 17.5.6 Step 6: Determining bearing capacity
⋄ section 17.5.7 Step 7: Checking for total soil weight criterion
⋄ section 17.5.8 Step 8: Adding pile weight

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17.5.1 Step 1: Reduction of the cone resistance due to overconsolidation

The cone resistance is based on CPTs. If the soil layers have been preloaded in the past
(overconsolidation) a correction for the OCR value has to be specified before starting the
calculation.The correction for over-consolidation is derived from the OCR values entered in
the Soil – Profiles window. The cone resistance will be reduced by:
r
1
qc;N C = qc;OC × (17.1)
OCR

17.5.2 Step 2: Reduction of cone resistance due to excavation

In most cases, the CPTs will be executed before excavation. As a result of the excavation both
the vertical stress and the cone resistance will decrease. According to NEN 9997-1+C2:2017,
the reduction of the cone resistance due to an excavation depends on the order in which the
excavation and installation take place.

When piles are installed after excavation (with a vibrating method), there is a linear ratio
between the cone resistance and the decrease in effective stress:
′
σv;z
qc;z;corr = qc;z × ′ (17.2)
σv;z;0
where:

qc;z;corr is the corrected cone resistance;

qc;z is the measured cone resistance;
′
σv;z is the effective vertical stress after excavation;
′
σv;z;0 is the effective vertical stress before excavation.

When piles are installed before excavation or if no or very little vibration is used, correction of
the cone resistance will be:
s
′
σv;z
qc;z;corr = qc;z × ′
(17.3)
σv;z;0

In both cases the corrected cone resistances are limited to a maximum of 12 MPa, or to
15 MPa if these values occur over a trajectory of 1 m or more.

The total vertical stress at a certain depth results from the integration of the unit weight of the
soil above the considered depth. By subtracting the water pressure at the considered depth,
the effective vertical stress is determined. An excavation reduces the vertical stress.

The determination of the effective stress after excavation is not given by NEN 9997-1+C2:2017.
In the tension piles model the stresses after excavation are determined as follows. The differ-
′ ′
ence between the effective vertical stress before and after excavation (σv;z;i - σv;z ) is equal
to the effective weight of the excavated soil per unit area. For the correction of the cone resis-
tance measured before excavation, the limited width of the excavation is taken into account.
For an excavation with limited width, the reduction of the vertical stress at a certain location
in the excavation can be determined relatively simply using stress distribution formulas for
a uniform strip loading (Poulos and Davis, 1974). D-F OUNDATIONS uses the elastic formulas

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for a uniform load with limited width to determine the change in effective stresses due to the
excavation. In the program this method is called Begemann.

The correction due to a limited width depends on the location of the pile and the depth of the
pile in respect to the excavation boundaries. The excavation is considered to be a uniform
strip unloading. The magnitude of the unloading is equal to the effective vertical stress at the
excavation level before excavation. The figure below shows the situation considered.

2b
p/unit area

01 02

δ
α

(x,z)

Figure 17.1: Determination of the change in effective stresses due to the excavation

The formulas for the decrease of the stresses are:

p
∆σz = [α + sin α cos (α + 2δ)] (17.4)
π

p
∆σx = [α − sin α cos (α + 2δ)] (17.5)
π

2p
∆σy = vα (17.6)
π
For piles at a distance x from the edge of the excavation α and δ can be determined from:
   
dmax dmin
α = arctan + arctan (17.7)
zexc − z zexc − z

 
dmin
δ = − arctan (17.8)
zexc − z
where:

dmin is the minimum distance between x (pile) and the edge of the excavation;
dmax is the maximum distance between x (pile) and the edge of the excavation;
z is the actual level;
zexc is the excavation level.

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The vertical stress after excavation is:

′ ′
σz,new = σz,old − ∆ σz (17.9)

Due to tension forces (see step 5 in section 17.5.5) negative stresses could occur in clay
layers due to excess pore water pressures. D-F OUNDATIONS sets all negative effective vertical
stresses to zero.

17.5.3 Step 3: Determination of the design value of the cone resistance (including safety
factors)
Design values are determined by:

⋄ correction by γγ for soil weight and therefore for vertical stresses

above phreatic level : γd′ = γ/γγ
⋄ ⋄

below phreatic level: γd′ = γwet /γγ − γwater

where γd′ must be greater than or equal to 0.
⋄ correction by γst , γm;var;qc and ξ for cone resistance.
The cone resistance is corrected according to:
qc;z;a
qc;z;d = γs;t ×γm;var;qc ×ξ

where γm;var;qc is determined by:

(Ft;max;k − Ft;min;k )
γm;var;qc = 1 + 0.25 × with γm;var;qc ≤ 1.5 (17.10)
Ft;max;k
where:

qc;z;a is the corrected cone resistance taking into account the grain size, the overcon-
solidation (step 1, Equation (17.1)) and the excavation (step 2, section 17.5.2);
ξ is the factor for the number of CPTs and the redistribution of the capacity (ξ = ξ3
respectively ξ = ξ4 ) and is determined based on Tables A.10a and A.10b from
NEN 9997-1+C2:2017.

It is known from test results that the bearing capacity of tension piles decreases with alternat-
ing loads, as compared to static loading. In D-F OUNDATIONS, as is common in design practice,
this effect is accounted for by using γm;var;qc to achieve a higher factor of safety for alternating
loads. (According to Deltares this is not, strictly speaking, correct – the effect of alternating
loads should be expressed in lower values for the shaft friction factor.)

17.5.4 Step 4: Determination of factor f1 (effect of installation)

A zone of soil compaction will develop around the piles due to installation. The influence of
soil compaction due to pile driving is determined on the basis of the following assumptions:

⋄ The pile displaces the soil grains (the volume of the soil grains does not change; at the
position of the pile there is no soil).
⋄ The pile displaces the soil grains only in the horizontal direction; this means that heave
of the soil due to the pile driving is not taken into account.
⋄ The effect of soil displacements decreases linearly over an area of 6Deq around the
pile.
⋄ The cone resistance is proportional to e3∆Re (Lunne and Christoffersen, 1983).

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⋄ The effect of higher tension due to soil displacement is assumed to be incorporated in

the calculation method, therefore calculated pore volumes may be smaller than physi-
cally possible (smaller than emin ).
⋄ Excavation of soil layers does not influence the cone resistance and packing of deeper
layers.

Based on these assumptions, the influence of pile installation is determined:

f1 = exp (3 × ∆Re ) (17.11)

with:
Pn
∆e 1
∆Re =
emax − emin
n
X (r − 6) (1 + e0 )
∆e = − × with r ≤ 6
1
5.5 50
e0 = −Re × (emax − emin ) + emax
 
1 qc;z
Re = × ln ′ 0.71
2.91 61 × σv;z;0
where:

e is the void ratio;

e0 is the actual void ratio, derived from the relative density at the moment the CPT
is executed;
emax is the maximum void ratio (specified in the Materials window, section 5.3.1);
emin is the minimum void ratio (specified in the Materials window, section 5.3.1);
r is the distance Deq from the considered pile to a neighboring pile;
qc;z is the measured cone resistance, in kN/m2 ;
′
σv;z;0 is the initial vertical effective stress at depth z , in kN/m2 .

Note: The factor f1 is always greater than or equal to 1.

Note: For relatively small values of the cone resistance, the relative density may have a
negative value. From a theoretical point of view, there is no objection to this, but a negative
value for the relative density causes numerical problems. Therefore, the relative density is
limited to a minimum of 0.

Note: When the pile installation factor is larger than 1.0, CPTs should be made after pile
installation to check the actual compaction rate. The number of CPTs should be equal to 1%
of the piles, with a minimum of 3 CPTs.

Note: In the Design Results window (section 7.2), two kinds of results are available for f1 :

⋄ f1 is the factor f1 at depth z

⋄ f1;aver. is the average factor f1 between pile head and pile tip. Materials for which
tension do not apply (i.e. option Apply tension in Figure 5.3 not marked) are not taken
into account.

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17.5.5 Step 5: Determination of factor f2 (effect of reduction of stresses due to tension

forces in pile groups)
Due to the distribution of tension forces over a finite area (the area around the pile in the pile
group, i.e. the area of influence) the vertical stress around the pile decreases. This effect is
accounted for in the factor f2 .

The factor f2 is based on the maximum uplift force on a certain depth, which can be found
using:

′ ′ Fmax;uplif t
σv;d;2 = σv;d;0 − (17.12)
A
where A is the area of influence around the pile in the pile group.

For determining A according to NEN 9997-1+C2:2017, D-F OUNDATIONS uses the following
method. The area around the pile is determined by means of the connection lines between
the considered pile and surrounding piles. These lines are divided equally and new lines
perpendicular to these lines are calculated. The smallest area within the new lines determines
the area of influence of the pile. This way, any point in the plan view belongs to the area of
influence of the pile closest to this point.

If the area around the pile is square or nearly square, as is the case in a regular pile pattern
(when using the Pile Grid option), A is determined by:

A = (center to center distance)2 − Apile (17.13)

A may also be an irregularly shaped area. The maximum ratio between the longest and
the smallest side length is always 2. When the ratio between the longest and the smallest
distance is larger than 2 the calculation method of the pile changes to an interval method.
The pile area is determined in the same way as described above. This area is divided in
segments. For each segment the maximum tension force is calculated, as if the pile area had
a radius equal to the radius of the segment. This calculation is repeated for all sections and
then the results are added to get the total tension force of the pile. This total tension force is
compared to the total soil weight criterion and the minimum value is the final bearing capacity
of the pile. See also NEN 9997-1+C2:2017.

The factor f2 represents the decrease in effective stress as a result of shaft friction along the
pile:
r
′ ′

 ′ ′
Pi−1 
−Mi + Mi2 + 2 × σv;j;0;d + γi;d × di × 2 × σv;j;0;d + γi;d × di − 2 × n=0 qt;n;d
f2;i = ′ ′


2 × σv;j;0;d + γi;d × di
(17.14)

with:

f1;i × Os;gem;i × αt × qc;i;d × di

Mi =
A
qt;i;d = Mi × f2;i
Xi−1
′ ′
σv;j;0;d = γn;d × dn
n=0

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17.5.6 Step 6: Determination of the maximum tension capacity Rt;d

The factor f2 is determined, varying with depth. The resulting shaft friction is calculated by
multiplying f2 by the shaft friction factor Mi :

qt;i;d = Mi × f2;i (17.15)

The sum of the shaft friction in all layers is equal to the design value of the maximum shaft
capacity:
m
X
Rt;d = A × qt;i;d with Rt;d ≤ Rt;kluid;d (17.16)
i=1

where:
Rt;kluid;d is the soil weight, in kN, calculated according to step 7 (section 17.5.7).

Note: For pile with enlarged base, the shaft friction is calculated along the total pile length,
not only along the base length.

17.5.7 Step 7: Determination of the total soil weight Rt;kluit;d

If the magnitude of the mobilized shear stress exceeds the effective weight of the soil body
surrounding a group pile, the pile will pull out this soil body. This means that the calculated
tension capacity of a pile in a group is limited by the effective weight of the soil body. This is
called the "total soil weight criterion" (Dutch: "kluitcriterium").

The effective weight of the soil body is determined by assuming that an arching effect occurs
in the soil between the piles. This means that the soil being pulled out with the pile has the
shape of a cone near the pile tips. The angle that the cone edge makes with the vertical is
denoted θ . This is presented in the figure below.

G*
d

piles
h
pile

θ θ

(D-d)/2
θ θ
tan θ
θ = 30o

θ = 45o

Figure 17.2: Pulled out soil geometry

The angle θ is related to the type of pile. For displacement piles θ is 45◦ within the pile group
and 30◦ at the edge of the group. For non-displacement piles θ is related to the internal friction
angle φ by 32 φ within the pile group and 21 φ at the edge of the group. In groups with large
pile distances the minimum value of the soil weight using the pile group value and the edge
pile value is determined as widely spaced piles may behave more like single piles than as a
group.

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For pile groups with a regular geometry, the square or nearly square area is transformed to a
circular area with radius R. The calculation of the height and volume of the cone is based on
this circular area.

For pile groups with irregularly shaped geometry (when using the method of segments) the
total pull-out soil weight is calculated by dividing the area into circular segments. The total soil
weight of the pile is equal to the sum of all segments.

Note: Comparison of total soil weight and shaft friction takes place only at the calculated pile
tip levels. For irregularly shaped pile geometry this comparison is made at pile tip level for the
pile as a whole, not for each segment.

17.5.8 Step 8: Addition of the pile weight

The total tension capacity of the pile includes the pile weight. If the pile weight is given as 0,
the pile weight is not taken into account. If the pile weight is > 0, the pile weight is included
in the calculations, even if the effective pile weight is smaller than the weight of the water and
the pile experiences uplift. The effect on the total bearing capacity is negative in such a case.

Note: According to art. 7.6.3.3(h) of NEN 9997-1+C2:2017, the pile weight is added to the
total tension capacity only for ‘soil displacing piles’ (i.e. ‘grondverdringende palen’ in Dutch).
D-F OUNDATIONS assumes that ‘soil displacing piles’ are piles for which the load-settlement
curve is curve 1, according to Table 7.c of NEN 9997-1+C2:2017.

The corresponding pile weight is calculated differently for different pile types:

H-profile
The following assumptions are relevant to the calculation of an H-profile pile type:

⋄ For the calculation of the shaft friction the entire outer area around the pile is taken into
account (i.e. the circumference is calculated using:
2 × Height of profile + 4 × Width of profile − 2 × Flange of profile).
⋄ Compaction of the soil is caused by the steel cross section of the pile.
⋄ A is the area of influence between the piles minus the outer area of the shaft friction.
(i.e. the “plugged” soil is not included in the area of influence.)
⋄ The weight of the pile is equal to the steel weight plus the soil weight within the shaft
friction area.

MV-pile
When calculating an MV-pile by using the H-profile input, the pile weight is calculated for the
steel area and the inside soil only. Grout weight is considered equal to soil weight.

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Open-ended steel pile

The calculation method for an open-ended steel pile consists of two parts:

⋄ Calculation according to NEN 9997-1+C2:2017 for outer shaft friction (A is area around
pile, compaction only by the steel surface of the neighboring piles, so the “plugged” soil
is not considered part of the area). Maximum shaft friction according to total soil weight
criterion (see section 17.5.7).
⋄ Calculation according to NEN 9997-1+C2:2017 for inner shaft friction (A is area inside
pile, no compaction, i.e. the area is only the area of the “plugged” soil). Maximum shaft
friction inside is weight of the soil in the pile until the pile tip level.
⋄ The sum of these two frictions is used to give the tension capacity.

Pile with enlarged base

For a pile with enlarged base, the pile weight is calculated using only the pile diameter/width
(but not the base diameter/width). This gives therefore a slightly lower value than the real pile
weight.

Piles near excavation

Piles at the edge of an excavation may be influenced by the excavation or its retaining walls.
These effects should be incorporated manually as described here. When calculating an edge
pile, the area of influence is NOT limited to the excavation boundary. The retaining wall is
considered to transfer shear stresses. When the users do not want to account for this shear
stress (because e.g. the walls are loaded) they need to add “virtual” piles opposite to the
retaining wall in order to achieve the required spreading area.

17.6 Problems in interpreting standards

The following are interpretation problems encountered while implementing the standard for
tension pile model:

⋄ NEN 9997-1+C2:2017 art. 1.5.2.128: Definition of a pile

It only makes sense to check the pile length (see section 17.1 for demands on pile
length) on the basis of the definition of a pile in this article if the phrase: "under ground
level" is inserted after "Element of which the length". The length of the pile above ground
level actually has no effect on whether the calculation model may be used or not.

⋄ NEN 9997-1+C2:2017 art. 7.6.2.3(k): Requirements related to the CPT

If there is any reduction of the qc values in the case of an excavation, the method to be
′
used to determine the effective vertical tension (σv;z ) is described in detail (Begemann).
However, D-F OUNDATIONS offers two methods for the reduction of qc values in the case
of an excavation. First there is the Safe (NEN) method which offers a more conservative
approach. Secondly the qc values can be reduced manually if needed. These options
can be found under Reduction of cone resistance in the Excavation window.

17.7 Units, dimensions and drawing agreements

It should be noted that the Tension Piles model (EC7-NL) is based on a semi 3-dimensional
approach. On a flat plane, this is expressed in the pile and CPT plans specified. The third
dimension (the depth) is recorded in the CPTs and the corresponding soil profiles. A fully
3-D approach, in which the piles can also be recorded to their full depth (raking piles), is not
considered desirable.

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The dimensional split in the flat plane on the one hand and in the depth on the other hand
also applies to the drawing agreements. In the flat plane, the users are completely free to
choose their own axis system for the pile and CPT plans. With regard to the depth, all levels
to be entered must be recorded in relation to the reference level. This reference level can be
chosen freely as long as it is used consistently throughout a project. In the Netherlands, the
most common reference level would be the Amsterdam ordnance zero (i.e. NAP). Here, levels
above the reference level are considered as positive and levels below the reference level as
negative. Settlements, however, are considered as positive if they are pointing downward (see
Figure 17.3).

A
+8

NAP

pile settlement +

expected soil
settlement +

-24 A

Figure 17.3: Sign conventions for settlements

The units of the input and output parameters in this model are displayed in Table 17.1. Al-
though it has been attempted to keep the units for the parameters equal to the units as they
occur in the standards, this has been deviated from in some cases. In those cases, in so far
as the requisite accuracy allows this, a larger unit was chosen to somewhat limit the length of
the figures to be entered and displayed. These deviant units are indicated in the table with a
* followed by the unit as mentioned in the standard.

In case of alternating loading of tension piles, the factor γm;var;qc is taken into account by en-
larging the safety factor for tension piles, γst . The factor γm;var;qc is determined based on the
characteristic values of both the maximum and minimum tension loads occurring. The mini-
mum tension load may be a compressive load. According to NEN 9997-1+C2:2017 tension
loads have to be entered as positive and compressive loads as negative values.

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Table 17.1: Units of the input/output parameters

Description Symbol Unit

Dry unit weight γunsat kN/m3
Wet unit weight γsat kN/m3
◦
Angle of true internal friction φ
Minimum void ratio emin -
Maximum void ratio emax -
Median mm
Maximum cone resistance kPa
Qc reduction %
Excess pore pressure at top kN/m2
Excess pore pressure at bottom kN/m2
Over-consolidation ratio OCR -
Shaft friction factor αt -
Pile Tip Level PTL m +/- NAP
Excavation level m +/- NAP
Cone resistance qc MPa
Unit weight water kN/m3
Surcharge p0 kN/m2
Tension force kN
Pull out force kN
Pile weight (calculated) kN

Coordinates of piles and CPTs for determining the positions in the pile and cone plans should
be specified in m.

17.8 Tension Piles schematics

The required data for executing a calculation for a pile foundation can be divided into two
groups: data related to the (foundation) construction (category superstructure, pile type, pile
dimensions, pile plan, etc.) and data used to typify the subsoil (CPTs with corresponding soil
profiles, including height groundwater level, excavation, etc.). When using the tension piles
model the relevant requirements of NEN 9997-1+C2:2017 and the capabilities and limitations
should be taken into account. These are explained in more detail in the following sections:

⋄ section 17.8.1 Problem boundaries

⋄ section 17.8.2 Variation in the pile tip level
⋄ section 17.8.3 Skin friction zone
⋄ section 17.8.4 Non rigid/rigid
⋄ section 17.8.5 Combination of superimposed load/excavation

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17.8.1 Problem boundaries

Because the D-F OUNDATIONS model cannot be supplied with unlimited memory, the limits given
in Table 17.2 apply to the maximum problem size.

Table 17.2: Limits applied to the maximum problem size

Maximum number of pile types 100

Maximum number of piles in pile plan 200
Maximum number of CPTs (i.e. soil profiles) 350
Maximum number of qc values per CPT 5000
Maximum number of layers per soil profile 100
Maximum number of iterations during design 151

17.8.2 Variation in the pile tip level

Although desirable, in practice the use of a single pile tip level in a project is not always
feasible. Variation in the soil layers for the executed CPTs may force designers to use different
pile tip levels.

The tension piles model therefore allows users to define the required pile tip level for each
CPT using the option Bearing capacity at fixed pile tip levels (section 5.6.2.2). In this way,
the user can cater for the above-mentioned variations. In the other design options, the pile tip
levels specified for each CPT are suppressed in favor of the pile tip trajectory. In that case,
the relevant pile tip level is retained as a starting point for each calculation step, or for each
pile tip level, for all CPTs.

It should also be noted that if the variations in the pile tip level are significantly large, the
project should be split into sub-projects, and the variations should be kept within limits in each
sub-project.

17.8.3 Skin friction zone

When designing tension piles according to NEN 9997-1+C2:2017, there are no restrictions
regarding the layers where friction is taken into account. In some cases (e.g. disturbed soil –
when relative soil-pile movements take place – or in layers with very low effective stress) the
user may explicitly want to exclude these layers. In D-F OUNDATIONS this can be achieved in
the following way:

⋄ In the Soil – Profiles window the top of the friction zone should be specified (sec-
tion 5.3.2.3). The tension capacity will be calculated from this level. According to
NEN 9997-1+C2:2017 the top of the friction zone should never be higher than 1 m
below ground level or excavation level.
⋄ In the Soil – Materials window, a soil material can be specified as having zero tension
capacity by setting the Apply tension value to False (section 5.3.1).

In peat layers the tension capacity is automatically taken as zero.

For skin friction the following restrictions always apply:

⋄ no skin friction is calculated above pile head level

⋄ no skin friction is calculated above ground and/or excavation level

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⋄ no skin friction is calculated in the first m of soil directly below ground or excavation
level (NEN 9997-1+C2:2017)
⋄ no skin friction is calculated in layers in which Apply tension is set to False
⋄ no skin friction is calculated in peat layers (αt = 0)

The weight of all soil layers with no friction is taken into account when determining effective
stresses and total soil weight. This also includes soil layers above the pile head level. The
skin friction zone can be entered at any level.

17.8.4 Non-rigid/rigid
One restriction when creating schematics is that for each calculation only (parts of) structures
that can be considered either as "completely rigid" or as "completely non-rigid" may be in-
cluded a single schematic. It follows that, for structures that are partly "non-rigid" and partly
"rigid" (for example, a building with a rigid core), the user must execute at least two calcula-
tions, one for the non-rigid part and one for the rigid part. Moreover, if the structure consists
of several different parts that can be considered as rigid, the user must execute a calculation
for each part. Figure 17.4 includes an example of division into sub-calculations.

1
2

Partial calculation 1: piles for rigid part of structure

Partial calculation 2: piles for non-rigid part of structure

Figure 17.4: Partial calculations for a mixed rigidity structure

For the definition of rigid/non-rigid, see NEN 9997-1+C2:2017 art. 7.6.1.1(c).

17.8.5 Combination of superimposed load and excavation

If a combination of a superimposed load (or surcharge) and excavation occurs, the following
restrictions apply when calculating the bearing capacity.

When designing building pits, the effect of excavations is taken into account. These exca-
vations have limited dimensions. Due to distribution of stresses in the sub-soil, the effect of
the limited excavation on the CPT value is less than for an unlimited excavation. This effect
is taken into account while determining the effect of the excavation. This means that one
excavation level is determined for the building pit and thereby for all the piles.

When using tension piles in a design that will be executed in phases, both the phase with

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maximum tension load and the phase with the minimum tension load should be considered
using two separate calculations. The sequence of phases (which can be defined in the Project
Properties – Construction Sequence window) is important when making calculations in this
type of project. Surcharge loads can only be included in the calculation when permanently
available so temporary surcharges should not be input. Surcharges are always considered to
apply only to the last phase in the building process.

Determining the effect of a surcharge load on the maximum bearing capacity is a complex
matter. In Dutch standards the positive effects of surcharge and its influence on the qc are not
taken into account. Therefore, the surcharge only has an influence on the effective stresses
and total soil weight. The size of the surcharge does not have to be specified by the user
as D-F OUNDATIONS assumes an infinite surcharge area. According to Deltares, this described
method is a safe approach. If required, the user can manually adjust qc by specifying reduction
percentages in the Excavation window.

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 18 Shallow Foundations model (EC7-NL)

18.1 Area of application

The shallow foundations model is used to design shallow foundations on the basis of the
Netherlands Eurocode 7 standards which has been implemented in NEN 9997-1+C2:2017
(NEN, 2017), and/or to verify them on the basis of this standard.

The model can be used to calculate and verify shallow foundations classified according to
Geotechnical Category 2 (GC2), which are subject to static or quasi-static loads. It is as-
sumed that the foundation surface is parallel with the horizon. Foundations laid on rock or in
cemented soil are not governed by NEN 9997-1+C2:2017 and therefore should not be ana-
lyzed using this model.

18.2 Limit states

The Dutch standards base the validation of constructions on three limit states. These are:

⋄ Limit state STR is the ultimate limit state for checking forces: i.e. is the foundation
strong enough to support the building.
⋄ Limit state GEO is the ultimate limit state for checking distortions (settlements and rota-
tions) of the ground: i.e. is the foundation solid enough to keep the building from being
torn, ruptured or dislocated.
⋄ Serviceability limit state is a serviceability limit state, only checking distortions at service
load.

18.3 Calculation process

This section includes an outline of how the verifications of the different limit sates prescribed
by the standards are processed into procedural step-by-step schematics suitable for use in a
computer model:

⋄ (section 18.3.1) Verifying limit state STR

⋄ (section 18.3.2) Verifying limit state GEO and serviceability limit state

18.3.1 Verifying limit state STR

Verification of limit state STR has been implemented in shallow foundations model in the
following way:

⋄ Every calculation starts by determining the effective foundation surface area (Aef ) on
the basis of the inputted loads and the foundation level. If it is necessary to redefine Aef
(for example, in the case of Punch calculations), the original Aef is used as a starting
point (see Figure 18.1).

⋄ Actual calculation begins by determining the maximum bearing capacity on the foun-
dation surface (bearing capacity in a vertical direction). It is determined whether the
undrained state can occur in the given problem definition. If so, the calculation method
(case a, b, or c) for the undrained state is selected and the pertinent calculations per-
formed. Note that Squeeze is checked for both case b and for case c even though only
case b refers to it. If the undrained state does not occur, the program immediately starts
determining the maximum vertical bearing capacity in the drained state. Here, too, the
correct calculation method is first determined prior to making the calculations.

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⋄ Determining the maximum horizontal bearing capacity is limited to a consideration of

the shear resistance Sh;d in relation to the horizontal load Fs;h;d . Active and passive
soil loads are not included in the calculations. In the majority of calculations, the simple
test Sh;d = Fs;h;d will be sufficient. If the passive earth pressure is still needed to
confirm the horizontal bearing capacity, the users must refer to NEN 9997-1+C2:2017
Chapter 9. Here, the users should remember that for full mobilization of the passive soil
load, relatively large deformations/displacements in the horizontal plane are necessary
(0.05 × foundation depth, see Table 9.c NEN 9997-1+C2:2017 art. 9.5.4(c)) and thus
they should bear in mind if the displacement of the foundation element is permissible.
⋄ Verification for limit state EQU is concluded with a consideration of the total stability
and the tilting stability according to the requirements in NEN 9997-1+C2:2017 article
6.5.4(1)P. If these are not satisfied, this is indicated by means of a reference to the
additional calculation methods of NEN 9997-1+C2:2017, Chapter 11.

Fs; v; d
Fs;v;d

Fs; h; d
Fs;h;d

sand, fairly solid

Aef
sand, solid

Aef'
clay, fairly solid

sand, solid

Aef = original effective foundation surface

Aef' = effective foundation surface with punch

Figure 18.1: Finding Aef

18.3.2 Verifying limit state GEO and serviceability limit state

Verification of limit state GEO and serviceability limit state is implemented in the shallow
foundations model in the following way:

When calculating the settlements, the so-called sun of Newmark (an alternative method of-
fered in NEN) is not used by D-F OUNDATIONS to determine the increase in stress. This graphical
method is not really suitable for use in a computer model, so the increase in stress is instead
calculated using the formula specified in the explanation of article 6.6.2(d) of NEN 9997-
1+C2:2017. An added advantage of this is that it provides the users with a control mecha-
nism, as they can now define the concentration value according to Fröhlich. The default value

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of 3 used by the program follows the model described by Boussinesq, whilst by entering the
value as 4 the user can simulate a stiffness that increases with depth.

Special attention should be paid to the accuracy of the calculated settlements, particularly in
the case of foundation elements for which the (effective) length/width ratio is much greater
than 1. The accuracy of the calculated settlement greatly depends on the calculated increase
in vertical effective stress. This is calculated for the middle of each layer, in accordance with
NEN 9997-1+C2:2017 art. 6.6.2(e), where the load must be distributed equally.

When the soil layers defined by the user are relatively thick, stress and increase in stress is
determined at only a few points (as there are only few layer medians). This may lead to a very
inaccurate calculation of the settlement. To prevent this occurring the program automatically
adds “dummy” layers at every 0.10 m in the profile. This enables the program to calculate the
increase of stress at a large number of points, greatly improving the accuracy of the calculated
settlement. When consulting the intermediate result file the extra layers, the calculated stress
and the increase in the calculated stress can all be seen (see also section 7.3.2.2).

To indicate the accuracy of the increase in stress achieved, its maximum value is expressed in
a percentage of the effective foundation pressure (Fs;v;d / Aef ). This percentage is included
with the results of the settlement calculation. If the increase in stress is less than 80% in
the first layer, it is also followed by a warning. Percentages greater than 100% are reduced to
100% by the program, which limits the maximum increase in stress to the value of the effective
foundation pressure. A second effect of the stress curve is that the stress increases seen
from below never become smaller (the curve is always descending with increasing depth). An
increase in stress is replaced by the deeper value if it is less than that "deeper" value.

Calculation and verification of the rotations occurring in a non-rigid structure is performed

on the basis of the relative settlements and distances between the centers of gravity of the
foundation elements. Rotation of an individual foundation element is not considered. For a
rigid structure, the rotations are set to zero in accordance with article 6.6.2(c) NEN 9997-
1+C2:2017.

18.4 Geometric problems

While developing the shallow foundations model, the following geometric problems were de-
tected:

⋄ When working with several foundation elements, it is important that they do not overlap.
D-F OUNDATIONS does not check for overlapping foundation elements as this test would
take up a disproportionate amount of space in the program. Moreover, the users can
easily and quickly check for overlaps themselves, since the foundation plan is displayed
graphically, to scale, in the Top View Foundation window.
⋄ A second problem involves the implementations of slopes. On the one hand, it is desir-
able that several different slopes can be used with different foundation elements, while
on the other hand the requisite input for this should remain limited. The chosen solution
was to define slopes fully independently and then merge them at a later stage with the
foundation element and soil profile. The slope is attached to the passive longitudinal
side of the element and bisects the layers in the soil profile. If necessary (for example,
in the case of a punch calculation) the angle β (NEN 9997-1+C2:2017 article 6.5.2.2(q))
will be automatically adjusted (see Figure 18.2).

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p
β

Aef

β: angle ground level - horizontal without punch

p: angle ground level - horizontal with punch

Figure 18.2: Slope adjustment for punch

18.5 Units, dimensions and drawing agreements

It should be noted that the Shallow Foundations model is based on a semi 3-dimensional ap-
proach. In the flat surface plane this is expressed in the foundation plan specified. The third
dimension (the depth) is recorded using the soil profiles. The split between the flat plane on
one hand and the depth on the other hand also applies to the drawing agreements. In the
flat plane, the users are completely free to choose their own axis system for the foundation
plan. With regard to the depth, all levels must be entered relative to the reference level. This
reference level can be chosen freely as long as it is used consistently throughout a project.
In the Netherlands, the most common reference level would be the Amsterdam ordnance
zero (i.e. NAP). In D-F OUNDATIONS, levels above the reference level are considered as posi-
tive. Settlements, however, are considered to be positive if they are pointing downward (see
Figure 18.3).

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+0,40

NAP

-0,60

detail A

detail A

+ settlement

Figure 18.3: Sign conventions for settlements

The units of the input parameters for the shallow foundations model are displayed in the table
below. Although it has been attempted to keep the units for the parameters equal to the units
as they occur in the standards, this has been deviated from is some cases. In such cases,
in so far as the requisite accuracy allows this, a larger unit was chosen to somewhat limit the
length of figures to be entered and displayed. These deviant units are indicated in the table
with a * followed by the unit as mentioned in the standards.

Table 18.1: Units of the input/output parameters

Description Symbol Unit

Berm width B [m]
Horizontal length of slope L [m]
Height of slope H [m]
Foundation level FL [m NAP]
Ground level [m NAP]
Groundwater level PL [m NAP]
2
Fröhlich’s concentration figure m [-]
Bottom layer level [m NAP]
Volumetric weight of soil γ [kN/m3 ]
Volumetric weight of saturated soil γsat [kN/m3 ]
Effective angle of internal friction φ’ [◦ ]
Cohesion c′ [kPa]

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Undrained shear strength fundr [kPa]

Primary compression index cc [-]
Secondary compression index cα [-]
(Initial) void ratio e0 [-]
Width of foundation element W [m]
Length of foundation element L [m]
Diameter of foundation element D [m]
X coordinate of foundation element [m]
Y coordinate of foundation element [m]
Angle (on a horizontal plane) of the length axis of foundation [◦ ]
element with the Y axis.
Eccentricity of the vertical load in the direction of latitude of the Eb [m]
foundation
Eccentricity of the vertical load in the direction of longitude of the El [m]
foundation
Calculated value of the vertical load in the limit state STR/GEO Vd;STR/GEO [kN]
Calculation value of the vertical load in the serviceability limit Vd;serviceability [kN]
state
Eccentricity of the horizontal load with respect to the bottom of El [m]
the foundation element
Angle (on a horizontal plane) of the horizontal load with the K [◦ ]
lengths of the foundation element
Calculated value of the horizontal load in the ultimate limit state Hd;EQU [kN]
(EQU)
Calculated value of the horizontal load in the serviceability limit Hd;serviceability [kN]
state
Maximum permissible settlement sreq [m]
Maximum permissible (relative) rotation βreq [m/m]

18.6 Shallow Foundations schematics

The requisite data for executing a (verification) calculation according to the Dutch standards
for a foundation can be divided into in two groups. One group of data consists of information
related to the (foundation) construction (superstructure category, dimensions, foundation plan,
etc.), while the other group involves data used to typify the subsoil (soil profiles including
height groundwater level, placement depth of the foundation element, etc.).

Various limitations should be taken into account, concerned with the following:

⋄ section 18.6.1 Problem boundaries

⋄ section 18.6.2 Variation in the level of the bearing layer
⋄ section 18.6.3 Non-rigid/Rigid
⋄ section 18.6.4 Merging sub-calculations

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18.6.1 Problem boundaries

Because the model cannot be supplied with unlimited memory, the limits given in Table 18.2
apply to the maximum problem size.

Table 18.2: Limits applied to the maximum problem size

Maximum number of foundation elements 20

Maximum number of soil profiles 350
Maximum number of layers per profile 100
Maximum number of loadings 20
Maximum number of slopes 20

18.6.2 Variation in the level of the bearing layer

Although desirable, in practice the use of a single foundation level in a project is usually not
feasible. Variation in the level of the bearing layer within the soil profiles often forces designers
to use different foundation levels.

The shallow foundations model therefore provides the option of defining the required foun-
dation level for each soil profile. In this way, the user can cater for the above-mentioned
variations.

18.6.3 Non-rigid/rigid
One restriction when creating schematics is that for each calculation only (parts of) structures
that can be considered either as completely “rigid" or as completely “non-rigid" may be in-
cluded a single schematic. If the structure is partly "non-rigid" and partly "rigid" (for example,
a building with a rigid core), at least two calculations, one for the non-rigid part and one for
the rigid part, must be performed.

Moreover, if the structure consists of several different parts that can be considered as rigid,
the user must execute a calculation for each part.

The reason for this restriction is that the model cannot be used to correctly determine the
relevant mutual distances – and therefore the mutual rotations– between the rigid and non-
rigid foundation elements.

For the definition of rigid/non-rigid elements, see NEN 9997-1+C2:2017 art. 7.6.1.1(c).

18.6.4 Merging sub-calculations

When splitting the problem definition into parts, the users should calculate and verify the rota-
tion between those parts them self, based on the maximum settlements in the limit state GEO
and serviceability limit state calculated for each part. The required centre-to-centre spac-
ing between rigid and non-rigid building components and between each of the rigid building
components should be carefully defined, if possible in consultation with the designer of the
superstructure.

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19 Benchmarks
Deltares Systems commitment to quality control and quality assurance has leaded them to
develop a formal and extensive procedure to verify the correct working of all of their geotech-
nical engineering tools. An extensive range of benchmark checks have been developed to
check the correct functioning of each tool. During product development these checks are run
on a regular basis to verify the improved product. These benchmark checks are provided in
the following sections, to allow the users to overview the checking procedure and verify for
themselves the correct functioning of D-F OUNDATIONS.

The benchmarks for D-F OUNDATIONS are subdivided into four separate groups as described
below.

⋄ Group 1 – Benchmarks for Bearing Piles (EC7-NL) model

⋄ Group 2 – Obsolete (Previously: Benchmarks for Bearing Piles (EC7-B) model)
⋄ Group 3 – Benchmarks for Tension Piles (EC7-NL) model
⋄ Group 4 – Benchmarks for Shallow Foundations (EC7-NL) model

All benchmarks are calculated using spreadsheets.

As much as software developers would wish they could, it is impossible to prove the correct-
ness of any non-trivial program. Re-calculating all the benchmarks in this report, and making
sure the results are as they should be, will prove to some degree that the program works as it
should.

Nevertheless there will always be combinations of input values that will cause the program to
crash or produce wrong results. Hopefully by using the benchmark verification procedure the
number of times this occurs will be limited.

The benchmarks are all described in detail in the Verification Report available via the Help
menu of the program (section 3.3.2).

The input files belonging to the benchmarks can be found in the local user directory:
.../Documents/Deltares Systems/D-Foundations/Benchmarks.

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20 Literature
Almere, 2016. Richtlijnen constructie gemeente Almere - Informatieblad voor ondernemers
en particulieren - Versie 3.0. Tech. rep., Gemente Almere.

CUR, 1992. “Publicatie 162: Construeren met grond Grondconstructies op en in weinig

draagkrachtige en sterk samendrukbare ondergrond.” Civieltechnischcentrum Uitvoering en
Regelgeving.

CUR, 2001. “Publicatie 2001-4: Design rules for Tension Piles.” .

GEOLib. Python package.

Lunne, T. and H. Christoffersen, 1983. “Interpretation of cone penetrometer data for offshore
sands.” Proceedings Offshore Technology Conference, OTC 4464 .

NEN, 1991a. NEN 6740:1991. Geotechniek - TGB 1990 - Basiseisen en belastingen

(Geotechnics - TGB 1990 - Basic requirements and loads), in Dutch.

NEN, 1991b. NEN 6743:1991. Geotechniek - Berekeningsmethode voor funderingen op palen

- Drukpalen (Geotechnics - Calculation method for bearing capacity of pile foundation -
Compression piles), in Dutch.

NEN, 1991c. NEN 6744:1991. Geotechniek - Berekeningsmethode voor funderingen op staal

(Geotechnics - Calculation method for shallow foundations), in Dutch. Nederlands Normal-
isatie Instituut (Dutch Normalisation Institute).

NEN, 2006. NEN 6743-1:2006. Geotechniek - Berekeningsmethode voor funderingen op

palen - Drukpalen (Geotechnics - Calculation method for bearing capacity of pile foundation
- Compression piles), in Dutch.

NEN, 2007. NEN 6744:2007. Geotechniek - Berekeningsmethode voor funderingen op staal

(Geotechnics - Calculation method for shallow foundations), in Dutch. Nederlands Normal-
isatie Instituut (Dutch Normalisation Institute).

NEN, 2012. NEN 9997-1+C1:2012 (nl). Geotechnisch ontwerp van constructies - Deel 1:
Algemene regels (Geotechnical design of structures - Part 1: General rules), in Dutch.

NEN, 2016. NEN 9997-1:2016 (nl). Geotechnisch ontwerp van constructies - Deel 1: Al-
gemene regels (Geotechnical design of structures - Part 1: General rules), in Dutch.

NEN, 2017. NEN 9997-1+C2:2017 (nl). Geotechnisch ontwerp van constructies - Deel 1:
Algemene regels (Geotechnical design of structures - Part 1: General rules), in Dutch.

Poulos, H. G. and E. H. Davis, 1974. Elastic Solutions for Soil and Rock Mechanics. New
York.

Robertson, P. and R. Campanella, 1983. “Interpretation of cone penetration tests, Part 2: Clay
Can.” Geotechnical Journal 20: 734-745.

WTCB, 2008. Richtlijnen voor de toepassing van Eurocode 7 in België - Deel 1: Het grond-
mechanisch ontwerp in uiterste grenstoestand van axiaal op druk belaste funderingspalen
(NL).

WTCB, 2010. Rapport nr 12 (NBN E25007 N006 N), Richtlijnen voor de toepassing van de
Eurocode 7 in België - Deel 1: Het grondmechanische ontwerp in de uiterste grenstoestand
van axiaal op druk belaste funderingspalen (Guidelines for the implementation of Eurocode
7 in Belgium, Part 1).

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 Photo’s by: BeeldbankVenW.nl, Rijkswaterstaat.

PO Box 177 +31 (0)88 335 81 88

2600 MH Delft software@deltares.nl
Boussinesqweg 1 www.deltares.nl/software
2629 HV Delft
The Netherlands