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Hard Rock Tunnel Boring Vol. 3 - Advance Rate and Cutter Wear

Thesis · October 2000

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 Advance Rate and Cutter Wear
Hard Rock Tunnel Boring
Doctoral theses at NTNU 1998:81

Amund Bruland

Vol. 3 of 10
NTNU Trondheim
Norwegian University of
Science and Technology
Doctoral thesis
for the degree of doktor ingeniør
Faculty of Engineering Science
and Technology
Department of Civil and
Transport Engineering
 PREFACE 1

0 GENERAL 3

0.1 Project Reports about Hard Rock Tunnel Boring 3

1 PARAMETERS 6

1.0 Introduction 6

1.1 Rock Parameters 7

1.2 Machine Parameters 10

2 NET PENETRATION RATE 14

2.0 Introduction 14

2.1 Fracturing 16

2.2 Rock Porosity 18

2.3 Basic Penetration 19

2.4 Basic Net Penetration Rate 21

2.5 Marked Single Joints 22

2.6 Torque Demand 24

2.7 Other Advance Rate Limitations 26

3 CUTTER LIFE 27

3.0 Introduction 27

3.1 Cutter Ring Life 32

4 GROSS ADVANCE RATE 33

4.0 Introduction 33

4.1 Machine Utilisation 34

4.2 Additional Time Consumption 40

APPENDICES 41

A. Previous Editions 41

B. Research Partners 42

C. List of Parameters 43

D. Estimation Forms 46
PREFACE

HARD ROCK TUNNEL BORING Advance Rate and Cutter Wear

Project Report 1B-98

The report is one of six reports about hard rock tunnel boring:

•= 1A-98 HARD ROCK TUNNEL BORING Design and Construction

•= 1B-98 HARD ROCK TUNNEL BORING Advance Rate and Cutter Wear
•= 1C-98 HARD ROCK TUNNEL BORING Costs
•= 1D-98 HARD ROCK TUNNEL BORING Geology and Preinvestigations
•= 1E-98 HARD ROCK TUNNEL BORING Performance Data and Back-mapping
•= 1F-98 HARD ROCK TUNNEL BORING The Boring Process

In addition, HARD ROCK TUNNEL BORING Background and Discussion gives

general information about the basis of the above listed reports.

Combined with the other reports in the Project Report Series from the Department of
Building and Construction Engineering at NTNU, the reports present an updated and
systematised material on rock excavation and tunnelling to be used for:

•= Economic dimensioning
•= Choice of alternative
•= Time planning
•= Cost estimates, tender, budgeting and cost control
•= Choice of excavation method and equipment.

A list of available Project Reports may be requested from the Department of Building
and Construction Engineering at NTNU.

The advance rate, cutter wear and excavation cost models also exist as a WINDOWS
programme.

The report is prepared by Amund Bruland and is part of his dr.ing thesis about
hard rock tunnel boring.

The reports listed above describe a comprehensive model developed at NTNU. The
model covers the complete tunnel boring process from the early planning stage

1
PREFACE

through preinvestigations, time and cost estimates, tunnel excavation and finally ac-
quisition and treatment of experience data. The models and data presented in the
reports are meant to be a practical tool for owners, consultants and contractors,
more than a theoretical analysis of the tunnel boring process.

The project has been granted financial support by our external research partners, see
list in Appendix.

For reference, registration and similar, we ask for the following:

NTNU-Anleggsdrift (1998): Project Report 1B-98 HARD ROCK TUNNEL

BORING Advance Rate and Cutter Wear.

When copying from the report, the source should be stated.

Trondheim, December 1998

Odd Johannessen
Professor

Contact address: Amund Bruland

Department of Building and Construction Engineering, NTNU
N-7034 Trondheim
NORWAY

Telephone +47 73 59 47 37 Fax +47 73 59 70 21

e-mail amund.bruland@bygg.ntnu.no
Internet http://www.bygg.ntnu.no/batek/batek.htm

2
0. GENERAL 0.1 Project Reports about Hard Rock Tunnel Boring

0.1 PROJECT REPORTS ABOUT HARD ROCK TUNNEL BORING

1B-98

The report provides methods and necessary data for estimation of time consump-
tion and cutter wear for tunnel boring. Geological parameters and machine factors
of significance for the penetration rate and the cutter wear are presented briefly.

The report presents the following data and models:

•= Chapter 1: Required rock mass and machine parameters to be used in the

estimation models.
•= Chapter 2: Estimation of net penetration rate.
•= Chapter 3: Estimation of cutter wear and cutter life
•= Chapter 4: Estimation of machine utilisation and weekly advance rate
•= Appendix D: Estimation forms adapted to the estimation models.

Project Report 1B-98 is a revised and updated version of parts of the Project Reports
1-76, 1-79, 1-83, 1-88 and 1-94, all published by the Department of Building and
Construction Engineering at NTNU.

Appendix A shows a list of previous editions of the report.

Other Reports

The Project Report 1A-98 HARD ROCK TUNNEL BORING Design and Con-
struction describes general design parameters such as tunnel profile, tunnel inclina-
tion and curve radius. Some features of various tunnel types like water, sewage, road
and rail tunnels are treated. Transport, ventilation and other necessary service systems
are presented.

The Project Report 1C-98 HARD ROCK TUNNEL BORING Costs presents
models and data for estimation of tunnel excavation costs and total construction costs.

3
0. GENERAL 0.1 Project Reports about Hard Rock Tunnel Boring

The Project Report 1D-98 HARD ROCK TUNNEL BORING Geology and Pre-
investigations treats the rock mass parameters of the model in more detail. Preinves-
tigations and building of an engineering geological model adapted to the estimation
models for penetration rate and excavation costs are treated closely.

The Project Report 1E-98 HARD ROCK TUNNEL BORING Performance Data
and Back-mapping covers follow-up procedures and collecting of performance data
from tunnel boring projects. Engineering geological back-mapping is treated in detail.

Project Report 1F-98 HARD ROCK TUNNEL BORING The Boring Process
covers rock breaking and chipping, machine factors affecting performance, boring in
fractured rock mass, and various types of cutter wear.

Use of the Estimation Models

The estimation models are aimed at being used through several stages in a project:

•= Preliminary and feasibility studies

•= Project design and optimisation
•= Tendering and contract
•= Construction
•= Possible claims.

The estimation models for Hard Rock Tunnel Boring should be used with care. Com-
bined with other estimation models in the Project Report Series from the Department
of Building and Construction Engineering, the Hard Rock Tunnel Boring reports pro-
vide a reliable and practical tool to be used for:

•= Estimating net penetration rate and cutter wear

•= Estimating time consumption and excavation costs, included risk
•= Assess risk with regard to variation in rock mass boreability or machine
parameters

4
0. GENERAL 0.1 Project Reports about Hard Rock Tunnel Boring

•= Establish and manage price regulation in contracts

•= Verify machine performance
•= Verify variation in geological conditions.

Background

The estimation models are based on job site studies and statistics from tunnelling in
Norway and abroad, including more than 35 job sites and more than 250 km of tunnel.
The data have been systematised and normalised. The results are regarded as being
representative for well organised tunnelling.

A more detailed treatment of the background and the basis for the Hard Rock Tunnel
Boring estimation models is found in HARD ROCK TUNNEL BORING Back-
ground and Discussion.

5
1. PARAMETERS 1.0 Introduction

1.0 INTRODUCTION

The net penetration rate depends on rock properties and machine parameters.

Rock Mass Parameters Machine Parameters

•= Fracturing; frequency and orientation •= Cutter thrust
•= Drilling Rate Index, DRI •= Cutterhead rpm
•= Porosity •= Cutter spacing
•= Cutter size and shape
•= Installed cutterhead power

Table 1.1 Machine and rock parameters influencing the net penetration rate.

The cutter wear depends on the following rock properties and machine parameters.

Rock Mass Parameters Machine Parameters

•= Cutter Life Index, CLI •= Cutter diameter
•= Content of abrasive minerals •= Cutter type and quality
•= Cutterhead diameter and shape
•= Cutterhead rpm
•= Number of cutters on the cutterhead

Table 1.2 Machine and rock parameters influencing the cutter wear.

The gross advance rate is estimated based on three input parameters:

•= Net penetration rate

•= Machine utilisation
•= Number of working hours in the period (e.g. a week).

The machine utilisation is again based on time consumption for the various operations
in the tunnel excavation process, see Chapter 4.

The estimation models apply to boring with single disc steel ring cutters.

6
1. PARAMETERS 1.1 Rock Parameters

1.1 ROCK PARAMETERS

To estimate time consumption and costs, an engineering geological preinvestigation,

adapted to tunnel boring, is required. This section gives a brief description of the
required geological parameters and may be an aid at an early planning phase. See
Project Report 1E-98 HARD ROCK TUNNEL BORING Geology and
Preinvestigations for detailed studies of geological conditions.

Degree of Fracturing

The rock mass fracturing is the most important penetration rate parameter for tunnel
boring. In this context, fracturing means fissures or joints with little or no shear
strength along the planes of weakness. The less the distance between the fractures is,
the greater the influence on the penetration rate is.

Rock mass fracturing is characterised by degree of fracturing (type and spacing) and
the angle between the tunnel axis and the planes of weakness.

Joints (Sp): Includes continuous joints that can be followed all around the tunnel
profile. They can be open (e.g. bedding joints in granite) or filled with clay or weak
minerals, e.g. calcite, chlorite or similar minerals.

Fissures (St): Includes non-continuous joints (can only be followed partly around the
tunnel profile), filled joints with low shear strength and bedding plane fissures, e.g. as
in mica schist or mica gneiss.

Homogenous Rock Mass (Class 0): Includes massive rock without joints or fissures
(may appear in intrusive dikes, sills, batholithes, etc.). Rock mass with filled joints of
high shear strength (e.g. joints healed with quartz, epidote, etc.) may approach Class
0.

The degree of fracturing in systematically fractured rock mass is divided into classes
for practical use when mapping (see Table 1.3). The classes include both distance
between and type of weakness planes. Figure 1.1 shows recorded fracture classes for
various rock types in bored tunnels.

7
1. PARAMETERS 1.1 Rock Parameters

Fracture Class Distance between

(Joints = Sp / Fissures = St) Planes of Weakness
[cm]
0 -
0-I 160
I- 80
I 40
II 20
III 10
IV 5

Table 1.3 Fracture classes with distance between the planes of weakness.

Amphibolite
Basalt
Gabbro
Gneiss
Granite
Granitic Gneiss
Limestone
Mica Gneiss
Mica Schist
Phyllite
Quartzite

0 0-I I I-II II II-III

III III-IV

few observations Fissure Class

frequently observed

Figure 1.1 Recorded degree of fracturing for some rock types.

Rock Drillability

Rock drillability is evaluated on the basis of the Drilling Rate Index DRI and the
Cutter Life Index CLI. The test methods are described in Project Report 13A-98
DRILLABILITY Test Methods. The Project Report 13B-98 DRILLABILITY
Catalogue of Drillability Indices lists 2000 samples tested in our laboratory.
Variation of DRI and CLI for some rock types is shown in Figures 1.2 and 1.3. The
influence of rock porosity is described in Section 2.2.

8
1. PARAMETERS 1.1 Rock Parameters

Amphibolite
Basalt
Diorite
Gabbro
Gneiss
Granite
Granitic Gneiss
Greenstone
Limestone
Marble
Mica Gneiss
Mica Schist
Phyllite
Quartzite
Sandstone
Shale
0 10 20 30 40 50 60 70 80 90
Drilling Rate Index, DRI
10% 25% 50% 75% 90% percentiles

Figure 1.2 Recorded Drilling Rate Index for some rock types. Data from Project
Report 13C-98 DRILLABILITY Statistics of Drillability Test Results.

Amphibolite
Basalt
Diorite
Gabbro
Gneiss
Granite
Granitic Gneiss
Greenstone
Limestone
Marble
Mica Gneiss
Mica Schist
Phyllite
Quartzite
Sandstone
Shale

0 10 20 30 40 50 60 70 80 90
Cutter Life Index, CLI
10% 25% 50% 75% 90% percentiles

Figure 1.3 Recorded Cutter Life Index for some rock types. Data from Project
Report 13C-98 DRILLABILITY Statistics of Drillability Test Results.
9
1. PARAMETERS 1.2 Machine Parameters

1.2 MACHINE PARAMETERS

To estimate the penetration rate and the cutter life, some machine parameters are
required. At an early stage of planning, the parameters must be assumed based on
general machine specifications.

TBM Diameter

Machines with diameters from 1.2 m to 12 m have been developed for boring in hard
rock. Considering the background data, the estimation models are applicable for TBM
diameters from 3 m to 10 m. The diameter of a given machine may be changed when
rebuilt. Modifications of ± 10 - 20 % are normal, depending on diameter and
manufacturer. For some machines the diameter may be changed even more; 100 %
from smallest to largest possible diameter.

Cutter Diameter

Over the recent years, the state of the art cutter diameter has increased from 394 mm
(15.5 inches) to 500 mm (19 and 20 inches). The increase is motivated by higher
cutter loads and longer cutter ring life. 483 mm has become the most used cutter size
for hard rock applications.

Cutter Thrust

Figure 1.4 shows a general outline of maximum gross average thrust per cutter disc as
a function of cutter diameter and TBM diameter. Gross average thrust means the
thrust the cutters are able to utilise over a longer period of time, not peak loads
occurring over short time intervals. At present, the material quality of the steel ring is
the limiting factor of the cutter thrust. When estimating penetration rate etc., one must
consider the thrust capacity of the cutter rings, in addition to the capacity of the cutter
bearings and the main bearing.

Cutterhead RPM

The cutterhead rpm is inverse proportional to the cutterhead diameter. This is because
one needs to limit the rolling velocity of the peripheral cutter. Figure 1.5 shows
cutterhead rpm as a function of TBM diameter and cutter diameter.

10
1. PARAMETERS 1.2 Machine Parameters

Number of Cutters on the Cutterhead

Figure 1.6 shows the standard number of cutters on a cutterhead as a function of

cutter diameter and TBM diameter. For the smaller TBM diameters, the available
space on the cutterhead is limited and the indicated number of cutters is the
maximum. For the larger TBM diameters, the number of cutters may be increased
compared to Figure 1.6.

Cutterhead Power

Figure 1.7 shows the installed power for cutterhead rotation as a function of cutter
diameter and TBM diameter. The installed power indicated should give sufficient
torque to handle a penetration rate of approximately 10 mm/rev for e.g. one stroke
length.

Figure 1.4 Recommended maximum gross average thrust per disc. The upper limit
indicates boring in homogenous rock mass, the lower limit indicates
boring in medium to very fractured rock mass.

11
1. PARAMETERS 1.2 Machine Parameters

14 1
RPM 1 dc=483mm
rev/min 2 2 dc=432mm
12
3 dc=394mm
3
4 dc=356mm
10
4
8

4.0 5.0 6.0 7.0 8.0 9.0

TBM diameter, m

Figure 1.5 Cutterhead rpm.

394mm
60 483mm
N0
50

40

30

20
3.0 4.0 5.0 6.0 7.0 8.0 9.0

TBM diameter, m

Figure 1.6 Normal number of cutters on the cutterhead.

12
1. PARAMETERS 1.2 Machine Parameters

Ptbm dc=483mm
kW

3000
dc=432mm

2000
dc=394mm

1000 dc=356mm

4.0 5.0 6.0 7.0 8.0 9.0

TBM diameter, m

Figure 1.7 Installed cutterhead power.

13
2. NET PENETRATION RATE 2.0 Introduction

2.0 INTRODUCTION

Net penetration rate is defined as metres tunnel bored per hour while the cutterhead
rotates with thrust against the face.

The penetration rate estimation model is based on normalised penetration curves, see
[2.1]. For more details, see Project Report 1F-98 HARD ROCK TUNNEL
BORING The Boring Process.

æM ö
i0 = ç ekv
çM (mm/rev) [2.1]
è 1

i0 = basic penetration rate

Mekv = equivalent cutter thrust in kN/c
M1 = critical cutter thrust in kN/c (necessary thrust to achieve 1 mm/rev)
b = penetration coefficient

The Figures 2.1 and 2.2 show the relation between the equivalent fracturing factor kekv
and the critical thrust M1 and the penetration coefficient b respectively.

200
M1
150

100

50

0
0 0.5 1.0 1.5 2.0 2.5 3.0

Equivalent fracturing factor, kekv

Figure 2.1 Critical thrust as a function of the equivalent fracturing factor.

14
2. NET PENETRATION RATE 2.0 Introduction

2.5
b
2.0

1.5

1.0

0.5

0
0 0.5 1.0 1.5 2.0 2.5 3.0

Equivalent fracturing factor, kekv

Figure 2.2 Penetration coefficient as a function of the equivalent fracturing factor.

The Estimation Forms in Appendix D may be used as examples of application and

will guide the user through all parts of the models.

15
2. NET PENETRATION RATE 2.1 Fracturing

2.1 FRACTURING

The rock mass fracturing is expressed by the fracturing factor ks, which is dependent
on the degree of fracturing (type and spacing) and the angle between the tunnel axis
and the planes of weakness, α.

The orientation of the weakness planes is determined from measurements of strike

and dip.

α = arcsin ( sin α f ⋅ sin ( α t - α s )) ( °) [2.2]

αs = strike angle
αf = dip angle
αt = tunnel direction.

The fracturing factor is shown in Figure 2.3, as a function of Fissure or Joint Class
and angle between the tunnel axis and the planes of weakness.

For more than one set of weakness planes, the total fracturing factor is as follows:

k si − (n − 1) ⋅ 0.36
n
k s −tot = [2.3]
i =1

ks-tot = total fracturing factor

ksi = fracturing factor for set no. i
n = number of fracturing sets.

The rock mass properties for TBM boring is expressed by the equivalent fracturing
factor.

16
2. NET PENETRATION RATE 2.1 Fracturing

k ekv = k s −tot ⋅ k DRI ⋅ k por [2.4]

kekv = equivalent fracturing factor

kDRI = correction factor for DRI of the rock
kpor = correction factor for porosity of the rock

kDRI
ks=0.36
1.2
ks=2.0
ks=3.5
1.0

0.8

0.6

0.4
20 30 40 50 60 70 80
DRI

IV
4.0
Fissure Class Joint Class
ks

3.0
III-IV

2.0

III II
II-III I-II
1.0
II I
I 0-I
0 0

10 20 30 40 50 60 70 80 90

 , degrees

Figure 2.3 Fracturing factor. Correction factor for DRI ≠ 50.

17
2. NET PENETRATION RATE 2.2 Rock Porosity

2.2 ROCK POROSITY

The porosity must be measured for rock types with porosity higher than
approximately 2 %. The porosity's influence on the DRI is negligible for porosity less
than 10 - 12 %. Hence, the porosity must be incorporated in the penetration rate
model as an independent parameter.

Boring in North Atlantic basalt (The Faeroe Islands) has shown that porosity has a
significant influence on the net penetration rate. The experience data are limited to
approximately 15 % porosity.

A rough estimate of the influence of porosity on the penetration rate is shown in

Figure 2.4.

5.0
kpor
4.0

3.0

2.0

1.0

2 4 6 8 10 12

Porosity, %

Figure 2.4 Influence of rock porosity on the equivalent fracturing factor.

18
2. NET PENETRATION RATE 2.3 Rock Porosity

2.3 BASIC PENETRATION

Basic penetration i0 as a function of equivalent thrust and equivalent fracturing factor

is shown in Figure 2.5. Equivalent thrust is given by [2.5]. Figure 2.6 shows the
correction factor kd and Figure 2.7 shows the correction factor ka.

M ekv = M B ⋅ k d ⋅ k a (kN/cutter) [2.5]

Equivalent thrust
i0
mm/rev

12.0 300kN/c

250kN/c
10.0

8.0 200kN/c

6.0
150kN/c

4.0

2.0

0.5 1.0 1.5 2.0 2.5

Equivalent fracturing factor, kekv.

Figure 2.5 Basic penetration. dc = 483 mm and ac = 70 mm.

19
2. NET PENETRATION RATE 2.3 Rock Porosity

1.3
kd
1.2

1.1

1.0

0.9

0.8
350 375 400 425 450 475 500

Cutter diameter, mm

Figure 2.6 Correction factor for cutter diameter dc ≠ 483 mm.

1.05
ka
1.00

0.95

0.90

0.85
60 65 70 75 80 85

Average cutter spacing, mm

Figure 2.7 Correction factor for average cutter spacing ac ≠ 70 mm.

20
2. NET PENETRATION RATE 2.4 Basic Net Penetration Rate

2.4 BASIC NET PENETRATION RATE

The basic net penetration rate I0 is a function of basic penetration and cutterhead rpm.
The basic net penetration rate is applicable for systematically fractured rock mass
without Marked Single Joints.

æ 60 ö
I 0 = i 0 ⋅ RPM ⋅ ç (m/h) [2.6]
è 1000

21
2. NET PENETRATION RATE 2.5 Marked Single Joints

2.5 MARKED SINGLE JOINTS

For a more detailed treatment of boring through Marked Single Joints, see Project
Report 1F-98 HARD ROCK TUNNEL BORING The Boring Process.

The model is based on a relatively small number of observations. The theoretical

penetration addition is shown in Figure 2.8. The normalised correction factor is
shown in Figure 2.9

The tunnel length lesp influenced by Marked Single Joints is estimated from the tunnel
diameter dtbm, the angle between the Marked Single Joints and the tunnel axis αesp,
and the number n of similar Marked Single Joints occurring in the geological zone.
αesp is found by [2.2].

l esp = n ⋅ d tbm / tan α esp (m) [2.7]

Net penetration rate when boring through Marked Single Joints, Iesp is found by

I esp = I 0 ⋅ k esp (m/h) [2.8]

kesp = correction factor for Marked Single Joints

kesp should not be given a higher value than 1.4. When the penetration addition is of
this size, the vibration level of the cutterhead and the peak forces on the cutters are
very high, requiring a reduction of the thrust level.

The average net penetration rate In over a geological zone with a total length of lj, is
found by

lj
In = (m/h) [2.9]
l j − l esp l esp
+
I0 I esp

22
2. NET PENETRATION RATE 2.5 Marked Single Joints

Penetration addition kesp, %

00 300 600 900

Angle between tunnel axis and single joint,  esp

Figure 2.8 Theoretical averaged penetration addition for marked single joints.

DRI=30 DRI=40
1.4

kesp DRI=50

1.3
DRI=60

1.2

1.1

10 20 30 40 50 60

 esp , degrees

Figure 2.9 Correction factor for Marked Single Joints.

23
2. NET PENETRATION RATE 2.6 Torque Demand

2.6 TORQUE DEMAND

For high net penetration rates or when boring in fractured rock, one must check that
there is sufficient cutterhead power installed to utilise the estimated thrust. The
machine is torque limited if the installed power is too low to rotate the cutterhead for
a given penetration. Then the thrust must be reduced until the required torque is less
than the torque capacity of the cutterhead drive. Necessary torque is given by:

Tn  rmc  d tbm  N tbm  M B  k c / 2 (kNm) [2.10]

rmc = relative position of the average cutter on the cutterhead. When the
cutterhead design is known, the factor may be calculated, see [2.11].
Normally, rmc is approximately 0.59.
dtbm = cutterhead diameter
Ntbm = number of cutters on the cutterhead
MB = gross average cutter thrust
kc = cutter coefficient (rolling resistance), see [2.12].

N tbm

r
i 1
i

N tbm
rmc  [2.11]
0.5  d tbm

ri = radius to position of cutter no. i

k c  cc  i0 [2.12]

Figure 2.10 shows the cutter constant cc as a function of cutter diameter. The
necessary torque decides the installed power. Necessary installed power is given by
[2.13].

24
2. NET PENETRATION RATE 2.6 Torque Demand

Tn ⋅ 2 ⋅ π ⋅ RPM
Pn = (kW) [2.13]
60

If the installed cutterhead power is less than Pn, the estimation of penetration rate
must me recalculated with a lower cutter load MB.

0.06
cc
0.05

0.04

0.03

0.02
300 350 400 450 500

Cutter diameter, mm

Figure 2.10 Cutter constant.

For more details on torque demand, see Project Report 1F-98 HARD ROCK
TUNNEL BORING The Boring Process.

25
2. NET PENETRATION RATE 2.7 Other Advance Rate Limitations

2.7 OTHER ADVANCE RATE LIMITATIONS

Besides limitations due to available torque, the system's capacity (the TBM and the
backup) for muck removal may limit the net penetration rate. Particularly, muck
removal may limit the net penetration rate for large diameter machines.

When boring through marked single joints or heavy fractured rock, it may be
necessary to reduce the thrust due to too high machine vibration level and very high
momentary cutter loads.

26
3. CUTTER LIFE 3.0 Introduction

3.0 INTRODUCTION

The estimation model presupposes that the TBM is operated at a thrust level resulting
in mainly abrasive wear of the cutter rings. The amount of blocked cutters and cutter
rings worn by ring chipping should be less than 10 - 20 % of the total number of
changed cutters.

The Estimation Forms in Appendix D may be used as examples of application and

will guide the user through all parts of the models.

27
3. CUTTER LIFE 3.1 Cutter Ring Life

3.1 CUTTER RING LIFE

The cutter ring life, in boring hours, is proportional to the Cutter Life Index CLI.
Figure 3.1 shows basic cutter ring life as a function of CLI and cutter diameter.

dc=483mm

140

H0
hr
dc=432mm
120

100

dc=394mm

80

dc=356mm
60

40

20

20 40 60 80 100

Cutter Life Index, CLI

Figure 3.1 Basic cutter ring life, H0 .

28
3. CUTTER LIFE 3.1 Cutter Ring Life

Correction for TBM Diameter

Correction factor for TBM diameter is shown in Figure 3.2. The centre and gage
cutters have a shorter lifetime than the face cutters. With increasing TBM diameter,
the ratio of centre and gage cutters to face cutters decreases, and the average cutter
will live longer.

1.6
kD
1.4

1.2

1.0

4.0 5.0 6.0 7.0 8.0 9.0

TBM diameter, m

Figure 3.2 Correction factor for TBM diameter.

Correction for Cutterhead RPM

The cutter ring life is inversely proportional to the cutterhead rpm, according to the
assumption that the time dependent wear is proportional to the rolling velocity of the
cutter. In other words: The cutter ring life in given rock conditions is constant if
measured in rolled distance, independent of the rolling velocity. The correction factor
for varying cutterhead rpm is shown in [3.1].

29
3. CUTTER LIFE 3.1 Cutter Ring Life

50 / d tbm
k rpm = [3.1]
RPM

dtbm = TBM diameter

RPM = cutterhead rpm.

Correction for Number of Cutters

When the actual number of cutters on the cutterhead differs from the model, the life of
the average cutter will change. Correction for actual number of cutters is:

N tbm
kN = [3.2]
N0

Ntbm = actual number of cutters

N0 = normal number of cutters (Figure 1.6).

Correction for Quartz Content

The cutter ring life varies with the rock content of quartz and other hard and abrasive
minerals. Figure 3.3 shows the correction factor as a function of quartz content only.
According to our experience, the content of minerals such as epidote and garnet may
be included in the quartz content when estimating the cutter ring life from Figure 3.3.

The correction factor in Figure 3.3 is based on normalised field and laboratory data.
For rock types of Group 1, the curve may be explained by the fact that the CLI and the
rock quartz content are not independent variables. Another possible explanation is
that the laboratory test procedures for the CLI are influenced by the mineral
composition of the rock.

30
3. CUTTER LIFE 3.1 Cutter Ring Life

When using the estimation model, CLI and rock quartz content should not be varied
independently. For rock types of Group 1, one should be cautious when using quartz
content close to 0 % and 27 %.

1.6
kQ 1 Mica schist
1.4 Mica gneiss
Gneiss
1.2 Granitic Gneiss
Granite
1.0

0.8
1
0.6

0.4
0 20 40 60 80 100

Quartz content, %

Figure 3.3 Correction factor for rock quartz content.

The average life of cutter rings is given by [3.3], [3.4] and [3.5].

H h = ( H 0 ⋅ k D ⋅ k Q ⋅ k rpm ⋅ k N ) / N tbm (h/c) [3.3]

Hm = Hh ⋅ In (m/c) [3.4]

H f = H h ⋅ I n ⋅ π ⋅ d tbm
2
/4 (sm3 /c) [3.5]

31
3. CUTTER LIFE 3.1 Cutter Ring Life

H0 = basic average cutter ring life

Hh = average cutter ring life in hours
Hm = average cutter ring life in metres
Hf = average cutter ring life solid cubic metres
In = net penetration rate
dtbm = TBM diameter.

H0 (and Ht , see Appendix D) expresses life of one individual cutter ring in the
average cutter position (≈ 0.59 ⋅ rtbm) in machine hours. E.g. for a CLI of 10 and a
quartz content of 30 %, one 483 mm diameter cutter ring will have a life of
approximately 70 hours in position 15 on a 3.5 m diameter TBM with standard
machine parameters.

Hh, Hm and Hf express averaged cutter life for the cutterhead or the tunnel. E.g. Hm =
10 m/c means that for each 10 m of tunnel, the total averaged wear on all the cutters
on the cutterhead corresponds to one complete cutter ring. Hm = 10 m/c also means
that, as an average, one has to change one cutter for every 10 m of tunnel bored.

32
4. GROSS ADVANCE RATE 4.0 Introduction

4.0 INTRODUCTION

Gross advance rate is given in metres per week as an average for a longer period.
Gross advance rate depends on net penetration rate, machine utilisation and the
number of working hours during the period.

The model is to a large extent based on experience data from a shift system that totals
approximately 100 working hours per week.

The machine utilisation includes only small amounts of rock support work. The model
is therefore not directly applicable for tunnels with substantial amounts of rock
support. The possibilities of changing cutters, performing maintenance and repair of
the TBM and the backup, etc., while installing the rock support, should be evaluated.

The Estimation Forms in Appendix D may be used as examples of application and

will guide the user through all parts of the models.

33
4. GROSS ADVANCE RATE 4.1 Machine Utilisation

4.1 MACHINE UTILISATION

The machine utilisation is net boring time expressed in per cent of total tunnelling
time. Total tunnelling time includes

•= Boring Tb
•= Regripping Tt
•= Cutter change and inspection Tc
•= Repair and service of the TBM Ttbm
•= Repair and service of the backup Tbak
•= Miscellaneous Ta.

The time consumption of the activities is expressed in hours per kilometre. Time
consumption used in this report is representative for the better part of today's
tunnelling practice. The machine utilisation is given by:

100 ⋅ Tb
u= (%) [4.1]
Tb + Tt + Tc + Ttbm + Tbak + Ta

Boring

The boring time depends on the average net penetration rate In.

1000
Tb = (h/km) [4.2]
In

Regripping

Time for regripping depends on the stroke length of the thrust cylinders and time per
regrip.

34
4. GROSS ADVANCE RATE 4.1 Machine Utilisation

1000 ⋅ t tak
Tt = (h/km) [4.3]
60 ⋅ l s

ls = stroke length, typically 1.5 - 2.0 m

ttak = time per regrip.

As an average, time per regrip ttak is 4.5 minutes. Time consumption varies with
gripper hold, the stroke length, the TBM diameter, boring in curves, and the capacity
of the hydraulic system. Under favourable conditions the time consumption will be
somewhat lower, but may increase substantially under difficult conditions.

Cutter Change

Time for cutter change and inspection depends on the cutter ring life Hh, the net
penetration rate In, and time used per changed cutter tc.

1000 ⋅ t c
Tc = (h/km) [4.4]
60 ⋅ H h ⋅ I n

Time per changed cutter varies with the cutter size. Typically, time consumption is

tc = 45 minutes for cutter diameter dc ≤ 432 mm (17 inches)

tc = 60 minutes for cutter diameter dc ≥ 483 mm (19 inches).

tc is based on data from cutterheads with front loaded cutters being changed under
favourable working conditions. Water ingress, unstable rock conditions, high rock
temperature, back loaded cutters, etc., may change the unit time substantially.

The inspection time per changed cutter increases when boring in rock with low
abrasivity. This gives an increased total time per changed cutter. Time per changed

35
4. GROSS ADVANCE RATE 4.1 Machine Utilisation

cutter also depends on number of cutters changed at one time. Few cutters changed
each round gives a higher unit time tc, and may also give reduced cutter life.

Other Activities

The time consumption for repair, maintenance and service of the TBM and the
backup, and miscellaneous activities, is shown in Figure 4.1. The time consumption is
representative for well organised tunnelling operations. Time for possible main
bearing failure and other long lasting stops is not included. Such risks must be
evaluated separately.

Miscellaneous includes the following activities:

•= Normal rock support in good rock conditions, i.e. rock support that may be
installed while boring and without increasing the tunnelling crew
•= Waiting for transport
•= Tracks or roadway; installation and maintenance
•= Surveying, moving of laser
•= Water, ventilation, electric cable; installation and maintenance
•= Washing and cleaning of the TBM and the backup
•= Other (change of crews, incidental lost time, etc.).

In addition to the listed items, miscellaneous includes time consumption related to the
tunnelling method and organisation.

For long headings (> 8 km), Miscellaneous demands an increasing part of the
available tunnelling time. Waiting for transport will increase substantially if the
capacity of the transport system is too low.

Continuous Conveyor

We have little data from TBM tunnelling using continuous conveyor for muck
transport. The few data available suggests that a conveyor based system has more stop
time than a rail based system, considering muck transport only. However, when the

36
4. GROSS ADVANCE RATE 4.1 Machine Utilisation

advantages of the conveyor-based system are incorporated fully into the total
tunnelling operations in long tunnels, we expect a machine utilisation equal to or
better than for a rail-based system.

In tunnels requiring a large amount of installations following the excavation (e.g. road
and railway tunnels), use of a continuous conveyor for muck transport is a good
solution to reduce the overall construction time.

Weekly Working Hours

Most of the data are taken from tunnelling operations based on approximately 100
working hours per week. Hence, it is presupposed some available time outside the
standard working hours to handle unforeseen and critical incidents like major repairs.
Some parts of such time consumption are not registered in the shift log and are
therefore not included in Figure 4.1.

Figure 4.2 indicates that the possibilities to handle unforeseen and critical incidents in
a flexible manner are fewer as the weekly working hours Tu increase towards 168
hours. Te expresses the available effective working hours when the weekly working
hours differ from 100, which is the basis for the model. The curve is based on relative
few observations, but is believed to be a conservative estimate regarding the loss of
effective working hours.

The weekly advance rate Iu will be:

I u = u ⋅ Te ⋅ I m / 100 (m/week) [4.5]

u = machine utilisation
Te = effective working hours per week
Im = average net penetration rate over the tunnel

37
4. GROSS ADVANCE RATE 4.1 Machine Utilisation

Figure 4.1 Time consumption for various activities.

38
4. GROSS ADVANCE RATE 4.1 Machine Utilisation

150
Available time, h/week

140

130

120

110

100

90

80

70

60
60 80 100 120 140 160

Weekly shift hours, h

Figure 4.2 Effective working hours per week.

39
4. GROSS ADVANCE RATE 4.2 Additional Time Consumption

4.2 ADDITIONAL TIME CONSUMPTION

Estimation of time consumption for a tunnel is based on weekly advance rate,

estimated on the basis of the net penetration rate and the machine utilisation. In
addition, extra time must be added for:

•= Excavation of underground assembly and start-up area, tip station, etc., if

necessary
•= Assembly and disassembly of the TBM and the backup in the tunnel, normally
from 4 to 8 weeks, mainly depending on the TBM diameter
•= Excavation of niches, branchings, etc.
•= Boring through and stabilising zones of poor rock quality
•= Additional time for unexpected rock mass conditions
•= Permanent rock support and lining work
•= Downtime TBM (additional time for possible major machine breakdowns)
•= Dismantling of tracks, ventilation, invert cleanup, etc.

Furthermore, time for manufacturing or refurbishing the TBM and the backup may
influence the overall time schedule, depending on the duration of the necessary
activities to precede the TBM excavation. Refurbishing a used TBM may take from 3
to 6 months. Manufacturing a new TBM may take from 6 months to one year,
depending mainly on the TBM diameter.

Transport of the TBM and the backup to the site may also be influence the overall
time schedule, for the same reasons as above. Transport of the TBM is a demanding
operation since the largest component may weigh 20 tons or more, even for a 3.5 m
diameter machine.

40
APPENDIX A. Previous Editions

A. PREVIOUS EDITIONS

Previous editions of Hard Rock Tunnel Boring Report including project group
members:

1-76 Norwegian edition

Bengt Drageset
Roy-Egil Hovde
Erik Dahl Johansen
Roar Sandnes
O. Torgeir Blindheim
Odd Johannessen

1-79 Norwegian edition

Knut Gakkestad
Jan Helgebostad
Svein Paulsen
Oddbjørn Aasen
Erik Dahl Johansen
O. Torgeir Blindheim
Odd Johannessen

1-83 Norwegian and English edition

Arne Lislerud
Steinar Johannessen
Amund Bruland
Tore Movinkel
Odd Johannessen

1-88 Norwegian and English edition

Arne Lislerud
Amund Bruland
Bjørn-Erik Johannessen
Tore Movinkel
Karsten Myrvold
Odd Johannessen

1-94 Norwegian and English edition

Bård Sandberg
Amund Bruland
Jan Lima
Odd Johannessen

41
APPENDIX B. Research Partners

B. RESEARCH PARTNERS

The following external research partners have supported the project:

•= Statkraft anlegg as
•= Norwegian Public Roads Administration
•= Statsbygg
•= Scandinavian Rock Group AS
•= NCC Eeg-Henriksen Anlegg AS
•= Veidekke ASA
•= Andersen Mek. Verksted AS
•= DYNO Nobel
•= Atlas Copco Rock Drills AB
•= Tamrock OY
•= The Research Council of Norway

42
APPENDIX C. List of Parameters

C. List of Parameters

The parameters used in the report are listed in the following. The list is according to
when the parameter first is explained or treated.

Parameter Description Unit Page

ac average cutter spacing - cutterhead mm 20

b penetration coefficient 14
cc cutter constant - torque demand 25
CLI Cutter Life Index 9
dc cutter diameter mm 10
dtbm TBM diameter m 10
DRI Drilling Rate Index 9
H0 basic cutter ring life - individual cutter h 28
3
Hf cutter ring life - cutterhead sm /c 31
Hfm averaged cutter ring life over the tunnel
- cutterhead sm3/c 53
Hh cutter ring life - cutterhead h/c 31
Hhm averaged cutter ring life over the tunnel
- cutterhead h/c 53
Hm cutter ring life - cutterhead m/c 31
Hmm averaged cutter ring life over the tunnel
- cutterhead m/c 53
Ht average cutter ring life over the tunnel
- individual cutter h 53
i0 basic penetration mm/rev 14
I0 basic net penetration rate m/h 21
Iesp net penetration rate including the effect of
Marked Single Joints m/h 22
In net penetration rate m/h 22
Im average net penetration rate over the tunnel m/h 37
Iu weekly advancerate m/week 37
ka correction factor for cutter spacing - penetration 20
kc cutter coefficient - torque demand 24
kd correction factor for cutter diameter
- penetration 20

43
APPENDIX C. List of Parameters

Parameter Description Unit Page

kD correction factor for cutterhead diameter

- cutter ring life 29
kDRI correction factor for DRI ≠ 49 - penetration 17
kesp penetration addition for Marked Single Joints 22
kekv equivalent fracturing factor 17
kN correction factor for no. of cutters
- cutter ring life 30
kpor correction factor for porosity - penetration 18
kQ correction factor for rock quartz content
- cutter ring life 31
kRPM correction factor for cutterhead RPM
- cutter ring life 30
ks fracturing factor 16
ksi fracturing factor for set no. i 16
ks-tot total fracturing factor 16
lesp tunnel length of Marked Single Joints m 22
lj lengt of (geological) zone no. j m 22
ls stroke length of TBM m 35
M1 critical thrust for 1 mm/rev penetration kN/c 14
MB gross average thrust per cutter kN/c 10
Mekv equivalent thrust per cutter kN/c 14
N0 normal no. of cutters on the cutterhead 12
Ntbm actual no. of cutters on the cutterhead 12
P rock porosity % 18
Pn necessary installed cutterhead power kW 25
Ptbm installed cutterhead power kW 13
Q rock quartz content % 30
ri position on cutterhead for cutter no. i m 24
rmc relative position of the average cutter position 24
RPM cutterhead revolutions rev/min 12
Sp type of fracturing - joints 7
St type of fracturing - fissures 7
Ta time for miscellaneous tunnelling activities h/km 34
Tb time for boring h/km 34
Tbak time for repair and service
of the backup h/km 34

44
APPENDIX C. List of Parameters

Parameter Description Unit Page

tc time per changed cutter min 35

Tc time for cutter change and inspection h/km 34
Te effective working (shift) hours m/week 37
Tn gross torque demand kNm 24
Tt time for regripping h/km 34
ttak time per regrip min 35
Ttbm time for repair and service of TBM h/km 34
Tu weekly working hours h/week 37
u machine utilization % 34
α angle between tunnel axis and
planes of weakness degrees(°) 16
αesp angle between tunnel axis and
Marked Single Joints degrees(°) 22
αf dip angle of planes of weakness degrees(°) 16
αs strike direction of planes of weakness degrees(°) 16
αt tunnel direction degrees(°) 16

45
APPENDIX D. Estimation Forms

D.1 Machine Data

Tunnel Date Signed

TBM diameter dtbm m Figure 1.4

Cutter diameter dc mm Figure 1.4

Cutterhead rpm RPM rpm Figure 1.5

Number of cutters on the cutterhead Ntbm Figure 1.6

Average cutter spacing

ac = dtbm · 1000 / (2 · Ntbm ) mm

Gross thrust per cutter MB kN/c Figure 1.4

Installed power Ptbm kW Figure 1.7

Relative position of the average cutter rmc [2.11]

Stroke length ls m Page 35

The Department of Building and Construction Engineering, NTNU, Trondheim 46

APPENDIX D. Estimation Forms

D.2 Geological Parameters

Tunnel/zone Date Signed

Length lj m

Drilling Rate Index DRI Figure 1.2

Cutter Life Index CLI Figure 1.3

Quartz content Q %

Rock group Figure 3.3

Porosity P %

Fracturing Class Figure 1.1

Set no. 1 Orientation α ° [2.2]

Fracturing factor ks1 Figure 2.3

Fracturing Class Figure 1.1

Set no. 2 Orientation α ° [2.2]

Fracturing factor ks2 Figure 2.3

Fracturing Class Figure 1.1

Set no. 3 Orientation α ° [2.2]

Fracturing factor ks3 Figure 2.3

k si − (n − 1) ⋅ 0.36
n
Total fracturing factor k s −tot = [2.3]
i =1

The Department of Building and Construction Engineering, NTNU, Trondheim 47

APPENDIX D. Estimation Forms

D.3 Net Penetration Rate

Tunnel/zone Date Signed

Rock mass fracturing factor ks-tot D.2

Correction for DRI ≠ 50 kDRI Figure 2.3

Correction for porosity > 2 % kpor Figure 2.4

Equivalent fracturing kekv = ks-tot · kDRI ⋅ kpor [2.4]

Gross thrust per cutter MB kN/c Figure 1.4

Correction for cutter diameter ≠ 483 mm kd Figure 2.6

Correction for average cutter spacing ≠ 70 mm ka Figure 2.7

Equivalent thrust Mekv = MB · kd · ka kN/c [2.5]

Basic penetration i0 mm/rev Figure 2.5

Cutterhead rpm RPM rpm Figure 1.5

Basic net penetration rate I0 = i0 · RPM · 60 / 1000 m/h [2.6]

The Department of Building and Construction Engineering, NTNU, Trondheim 48

APPENDIX D. Estimation Forms

D.4 Net Penetration Rate (including correction for Marked Single Joints)

Tunnel/zone Date Signed

Length of zone lj m

Tunnel length of Marked Single Joints lesp m [2.7]

Basic net penetration rate I0 m/h D.3

Drilling Rate Index DRI Figure 1.2

Orientation of Marked Single Joints αesp ° [2.2]

Correction for Marked Single Joints kesp Figure 2.9

Penetration rate in Marked Single Joints

Iesp = I0 · kesp m/h [2.8]

Average net penetration rate of the zone

In = lj / ((lj - lesp ) /I0 + lesp / Iesp ) m/h [2.9]

The Department of Building and Construction Engineering, NTNU, Trondheim 49

APPENDIX D. Estimation Forms

D.5 Torque Control

Tunnel/zone Date Signed

Relative position of the average cutter rmc [2.11]

TBM diameter dtbm m D.1

Number of cutters Ntbm Figure 1.6

Gross thrust per cutter MB kN/c Figure 1.4

Cutter diameter dc mm D.1

Cutter constant cc Figure 2.10

Basic penetration i0 mm/rev Figure 2.5

Cutter coefficient kc = cc · √i0 [2.12]

Required torque Tn = rmc · dtbm · Ntbm · MB · kc / 2 kNm [2.10]

Cutterhead rpm RPM rpm Figure 1.5

Required power Pn = Tn · 2 · π · RPM / 60 kW [2.13]

Installed power Ptbm kW Figure 1.7

If the installed power is insufficient to meet the required torque, the estimation of net
penetration rate and required power must be repeated with a lower gross thrust per
cutter.

The necessary torque is estimated without including Marked Single Joints.

The Department of Building and Construction Engineering, NTNU, Trondheim 50

APPENDIX D. Estimation Forms

D.6 Cutter Ring Life

Tunnel/zone Date Signed

Cutter Life Index CLI Figure 1.3

Quartz content Q % D.2

Rock group Figure 3.3

Basic cutter ring life H0 h Figure 3.1

Correction for TBM diameter kD Figure 3.2

Correction for quartz content kQ Figure 3.3

TBM diameter dtbm m D.1

Cutterhead rpm RPM rpm Figure 1.5

Correction for cutterhead rpm

kRPM = (50 / dtbm ) / RPM [3.1]

Number of cutters on the cutterhead Ntbm Figure 1.6

Standard number of cutters N0 Figure 1.6

Correction for number of cutters kN = Ntbm / N0 [3.2]

Cutter ring life Hh = H0 · kD · kQ · kRPM · kN / Ntbm h/c [3.3]

Net penetration rate In m/h D.4

Cutter ring life Hm = Hh · In m/c [3.4]

Cutter ring life Hf = Hh · In · π · dtbm2 / 4 sm3/c [3.5]

The Department of Building and Construction Engineering, NTNU, Trondheim 51

APPENDIX D. Estimation Forms

D.7 Net Penetration Rate, Average Over the Tunnel

Tunnel Date Signed

Zone no. j 1 2 3 4 5

Length lj (m)

Net penetration rate Inj (m/h)

Σl j
Average net penetration rate Im Im = = (m/h)
Σ(l j / I nj )

The Department of Building and Construction Engineering, NTNU, Trondheim 52

APPENDIX D. Estimation Forms

D.8 Cutter Ring Life, Average Over the Tunnel

Tunnel Date Signed

Zone no. j 1 2 3 4 5

Length lj (m)

Net penetration rate Inj (m/h)

Cutter ring life Hhj (h/c)

Cutter ring life Hmj (m/c)

Cutter ring life Hfj (sm3/c)

Σ(l j / I nj )
Average cutter ring life H hm = = h/c
l j / I nj
Σ( )
H hj

Σl j
Average cutter ring life H mm = = m/c
Σ(l j / H mj )

Σl j
Average cutter ring life H fm = = sm3/c
Σ(l j / H fj )

Average cutter ring life H t = H hm ⋅ N tbm = h/c

The Department of Building and Construction Engineering, NTNU, Trondheim 53

APPENDIX D. Estimation Forms

D.9 Machine Utilisation and Weekly Advance Rate

Tunnel Date Signed

Net penetration rate Im m/h D.7

Boring time Tb = 1000 / Im h/km [4.2]

Stroke length ls m Page 35

Time per regrip ttak min Page 35

Regripping time Tt = 1000 · ttak / (60 · ls ) h/km [4.3]

Time per changed cutter tc min Page 35

Cutter ring life Hhm h/c D.8

Cutter time Tc = 1000 · tc / (60 · Hhm · Im ) h/km [4.4]

Repair and service of TBM Ttbm h/km Figure 4.1

Repair and service of backup Tbak h/km Figure 4.1

Other time consumption Ta h/km Figure 4.1

Machine utilization
u = (100 · Tb ) / (Tb + Tt + Tc + Ttbm + Tbak + Ta ) % [4.1]

Nominal working hours Tu h/week Page 37

Effective working hours Te h/week Figure 4.2

Weekly advance rate Iu = u ⋅ Te · Im / 100 m/week [4.5]

The Department of Building and Construction Engineering, NTNU, Trondheim 54

 ISBN 82-471-0281-1
ISSN 0802-3271

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