HKIE Geotechnical Division &

Dept of Civil & Env Engineering, Hong Kong of Science and Technology

Top-up Course for TCP T3 on GIFW and Building Works with Significant Geotechnical Content

GEOGUIDE 2

Ir. Alice Lai

Senior Geotechnical Engineer, Geotechnical Engineering Office

Department of Civil & Development Engineering, HKSAR Government
The Geoguide (2017 version) is continuously updated in e-format.
https://www.cedd.gov.hk/eng/publications/geo/geo_g2.html

2
Geoguide 2

Part I – Introduction
Part II – General Considerations
Part II I – Planning the Ground Investigation
Part IV – Ground Investigation Methods
Part V – Field and Laboratory Tests
Part VI – Reports and Interpretation

4
 General Considerations

• Site Investigation (地盤勘測) or Ground

Investigation (土地勘探)?

Site Investigation (SI) includes

• Desk Study (Appendix A of Geoguide 2)
• Site Visit (Appendix C of Geoguide 2)
• Preliminary Site Assessment
• Ground Investigation (GI)
Objectives of Site Investigation

• Suitability/ Choice of site

• Adequate and economical design
• Best method of construction
• Effect of change
• Stability/Post-failure investigation
 Preliminary Stage
Obtain basic information of ground
conditions, site constraints, etc.
Site reconnaisance to establish geological
model or design concept

Main Stage
Detailed GI- focus on specific issues,
refine geological model, obtain
geotechnical engineering data,
undertake in-situ testing and/or
monitoring, modify/finalize detailed
design
Construction Stage
Record actual ground
conditions, design review, Post-construction Stage
additional GI may be needed Specific GI - monitor
to modify design behaviour or effect of
works on adjacent sites
 Desk Study
• Site topography

• Site history

• Adjacent property, land status

• Service/utilities at the site

• Geology, hydrogeology and geomorphology

• Potential geotechnical problems

• Anticipated hazards in relation to the proposed construction

• Estimated cost of a ground investigation

 Topographic Maps (1)
• (Obtainable from Survey and Mapping Office, Lands
Department)
https://www.landsd.gov.hk/mapping/welcome.htm

• Hard copy and digital form

• Scale
– from 1 :1000 to 1: 200 000
– 1:5 000 (useful as location map)
– 1:1 000 (useful to study detailed site topography and
development)
 Topographic Maps (2)
• Identify ground features of engineering significance
e.g. slopes, retaining structures, tunnels, graves, pylon,
pipeline (obstruction)

• Adjacent properties, structures

• Identification of works areas, storage areas, etc.

• Footpath, access for site visit (walk over survey)

• Important Note – due to rapid development in Hong

Kong , walk over survey is required to confirm the
existence of such features
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2020/3/22 Planning & Design of GI 13
2020/3/22 Planning & Design GI 14
 Aerial Photographs (vertical or oblique)
• Oldest photos – 1924

• Stereopair – 3D images

• can delineate

– Topography
– Geomorphology
– Photolineament
– Past instability
– Site development history
Aerial Photographs (vertical or Oblique)
• can delineate
– Location of boulders

– Drainage lines

– Rockhead

– Extent of colluvium

– Slope gradient

– Weathering

– Identification of slope condition (natural or man-made)

– Erosion
Ho Man Tin 1949
17
Kai Tak
1954

Kai Tak
1964

18
http:/www.cedd.gov.gk/eng/about/organisation/org_geo_pln_serv.html

19
http://www.landsd.gov.hk/mapping/en/paper_map/photo.htm
Oblique Aerial Photo - Hong Kong (6 000’) 1996
21
Oblique Aerial Photo - Tuen Mun (4 000’) 1996
22
Vertical Aerial Photo - Tuen Mun (4 000’) 2000
23
Vertical Aerial Photo - Nam Chung (3 500’) 1999
24
Infrared Aerial Photo – Sai Kung (6 000’) 2008
 Ortho-rectification
• The distortion in an air photo
may be taken out by digital
techniques to produce
orthophotos.

• Geometric distortions and relief

displacements are removed.

26
 Ortho-rectification

• They are images with correct

horizontal scale and positional
relationships, after ortho-
rectification process.

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Stereoscope
29
Pocket Stereoscope
30
 Geotechnical Studies Programme (GASP)

• Based on terrain classification techniques

using aerial photographs supplemented by
site mapping
• Give regional geotechnical information for
territory-wide planning purposes
• Provide a basis for engineering feasibility
studies of large sites
• 1: 20 000 scale map
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 Old Maps, Photos, Publications
• Site history
• Old seawalls, stream courses, Archaeological
site
• Antiquities & Monuments Office, Leisure and
Cultural Services Department
(https://www.amo.gov.hk/en/main.php)
Ordinance Map of Hong Kong in 1896 37
38
1880

1988

41
Chater Hall
Conduit Road
1966

42
Po Shan Road Landslip in 1972 43
 Geological Maps
• Provide general geological information of the
project area

• Used for evaluating the likely influence of the

local geology on the proposed works and in
the selection of the GI methods
 Geological Maps
• 1:50 000 • Allen & Stephen (1971) – outdated

• 1:20 000 • Hong Kong Geological Survey, GEO

(since 1982)
– Currently being revised based on GI data and
underground engineering projects. Updated
maps will be released on GIS platform)

• 1: 5000 • Hong Kong Geological Survey, GEO

– North Lantau and marble areas ( Yuen
Long, Ma On Shan)
 Geological Maps
• Surface geology (distribution of rock types)

• Rock type (igneous, sedimentary, metamorphic rocks)

• Geological structures – joints, faults, bedding plans

• Metamorphic zone

• Degree of metamorphism

• Contact between different rock types

• Extent of fill

• Extent of colluvium

• Marine deposit

• Reclamation

• Marble

• Stratigraphy (geological history)

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General Geological Map of Hong Kong
48
Distribution of Faults
1:20 000 Geological Map - Lantau Island
50
Geological Section

51
 Geological Memoirs
• Describe the solid and superficial geology
– Lithology
– Distribution of rock types
– Relationship between rock types
– Engineering geological problems
– Marble
– Fault zone
– Hydrothermal alteration area – clay seam, relict joint

(https://www.cedd.gov.hk/eng/publications/services/index.htm)
54
GI Records
Existing Ground Investigation Records
• Information can be from GI records:
– Ground conditions for geological profile
– Groundwater levels
– Piezometeric data
– Geological structure
– Laboratory test results e.g. soil parameters, rock
strength
– Rock joint mapping
Geotechnical Information Unit (GIU)

Established in 1983

Forms part of the CEL and houses a

comprehensive collection of geotechnical
data from ground investigations throughout
the Hong Kong SAR.
 Geotechnical Information Unit
• The following GIU materials are among those available for inspection by
the public:

– GI reports, including geophysical surveys

– Reports on laboratory testing of soil and rock, and chemical & biological testing

– Landslip record cards

– Piezometric monitoring data

– An inventory of landslides on natural terrain

– Locations for government slopes and hillside catchments which have been
upgraded and mitigated or which are included in current works contract under
the Landslip Prevention and Mitigation Programme (LPMitP)

– AGS data for some GI reports and lab testing reports

Digital Geotechnical Information Unit (DGIU)

System is available for fast retrieval of these reports in

the CEL and developed to replace GILS

Launched in July 2009

This system has a GIS engine to support spatial and

textual searches to help users locate the needed
information efficiently, and to view and print digital GI
reports

A user’s manual for the DGIU is provided in the CEL.

Digital Geotechnical Information Unit

http://ginfo.cedd.hksarg/arcgisweb/admin/homepage.aspx#
Digital Geotechnical Information Unit
Natural Terrain Landslide
Inventory
Aerial Photograph Interpretation – Compilation of Natural Terrain Landslide Inventory
Enhanced Natural Terrain Landslide Inventory (ENTLI)

The ENTLI contains information on over 100,000

landslides occurred on natural terrain.

Comprehensive information is recorded in GIS System

for each landslide record including the dates of the
aerial photographs when the landslide was first
observed, width and length of the landslide scar,
slope gradient, and nature of vegetation cover across
the landslide source.
Enhanced Natural Terrain Landslide Inventory (ENTLI)

The ENTLI is available for inspection as 1:5 000 scale

map sheet paper copies in the CEL and the digital
copy of the data is by the PTE Section of the GEO

The inventory is regularly updated to the latest aerial

photos
 Territory-wide LiDAR Survey

 Data Capturing: Dec 2010 to Jan 2011

 Total Flight Time: 44 hours

Multi-Return Airborne LiDAR
Virtual Deforestation – removal of
vegetation cover

1st return from tree top

2nd return from branches

1st (and only) return
from ground
Last return from ground
LiDAR Ground Piont Cloud
LIC contour (2m)
Facilitate
visualisation of
landslide
morphology

Lidar contour (1m)

LiDAR Derived Contours
at Yi O, Lantau
3-D Bare Earth Model of Wang Hang Landslides
3-D Image of 2008 Landslide Scar behind the University of Hong Kong
Boulder Field Inventory
Boulder Field inventory in Planning Division of GEO
Slope Information System (SIS)
http://hkss.cedd.gov.hk/hkss/eng/sis.aspx
Construction Records
 Construction Records (1)
• Seawall/retaining wall – as built drawing
(geometry, material, etc.)

• Foundation – location of piles, foundation levels

• Slope installation – ground anchors, soil nails,

horizontal drains

• Slope movement records – tell-tale, inclinometer

monitoring records, etc.
 Construction Records (2)
• Tunnel and disused tunnels (alignment & conditions) – GEO

• Private Buildings – Building Department

• Government Buildings – Architectural Services Department

• Quarries and Mines – GEO

• Road and road tunnels – Highways Department

• Landfills – EPD

• Sewerage pipes – Drainage Services Department

• Electricity cables, Gas pipes, telephone cables, cable TV, etc.

 Other useful information (1)
• Lands Matters (Lands Department)
– https://www.landsd.gov.hk
– Lease and engineering conditions
– Layout of site
– Site boundary
• Environmental Restriction (Environmental
Protection Department)
– https://www.epd.gov.hk
 Other useful information (2)
• Land Use (Planning Department)
– https://www.pland.gov.hk
– Outline Zoning Plan (OZP)
• Prepared by Town Planning Board
• Shows the proposed land-use zoning and major
systems of individual planning scheme ares
– Development Permission Areas (DPA)
• Prepared for an area not previously covered by OZP
• Land use information not as detailed as an OZP
• Serve as a control to unauthorized development in the
rural areas
 Other useful information (3)

• Scheduled Areas of Mid-levels Northwest New

Territories, Ma On Shan, MTR Railway
Protection Plan and Sewage Tunnel Protection
Areas
• Designated Area of Northshore Lantau (ref:
GEO TGN. 12)
• List of Ecologically Important Streams/Rivers
(ref: Appendix A of ETWB 5/2005)
 Scheduled Area No 1 (Mid-levels Area)

Scheduled Area No. 2 – North-Western

Part of the New Territories
 Designated Area of Northshore Lantau

Scheduled Area No. 4

(Ma On Shan Area)
 Scheduled Area No. 3 (Railway
Protection Areas)

Scheduled Area No. 5 (The Sewage

Tunnel Protection Areas)
 Other GEO Publications
• https://www.cedd.gov.hk/eng/publications/geo/index.html

• Many useful documents such as

– GEO Technical Guidance Notes
– GEO Publication e.g. 1/2007
– GEO Reports
– Standards, Specifications and Handbooks
– Information on Laboratory Testing
 Site Reconnaissance (1)
• Confirm and supplement the information gather from desk study

– Topography – gradient

– Geology – lithology, thickness of soil mantle

– Rock joints

– Weathering

– Fault zones

– Fill

– Erosion

– Potential geotechnical hazards

 Site Reconnaissance (2)
– Site accessibility

– Drainage pattern possible environmental impact – wetland, mangrove, birds

– Graves, temples, Tse Tong

– Vegetation – tree survey

– Catchwater – possible division

– Access road – further land access

– Existing structures

– Illegal occupation of land

– Availability of water and electricity

– Possible objection to the development (village visit)

Walk over survey - Lamma Quarry
93
Planning of Ground Investigation
Ground Investigation
Purposes:
(a) Recovering soils and rocks for establishment of geological profiles,
weathering intensity
(b) Field Installation - Piezometers (Water Pressure)
- Observation Wells (Water Levels)
- Inclinometers (Slope Movements)
(c) Sampling
(d) Field Testing - Standard Penetration Test (N Values)
- Permeability Tests (Falling, Rising or Constant Heads)
- Impression Packer/borehole televiewer
- Vane Shear Test
- Dynamic Probe
- Sand Replacement (in Trial Pits)

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• Preliminary Site Assessment

– Consolidate existing data from Desk Study

– Integrate with site visit findings

– Check project and engineering requirements

– Propose further GI works, if any

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Extent of Ground Investigation
• Investigation Locations
• Investigation Stations Spacing
• Investigation Depths
• Investigation Methods

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 GI Cost Analysis
Cost - Benefit Curve
120

100 Trial construction /

excavation / testing

80
Benefit

Boreholes, testing,
instrumentation
60
Geophysics
40

20
0 20 40
Cost ($)60 80 100

Low High
98
 BH1+

Site

BH3+

BH2+

0 200 m

99
 0
BH1 BH3

Fill
Fill

Residual Soil
Residual Soil

Completely
Completely Decomposed
Decomposed Granite
Granite

Slightly
Slightly Decomposed
Decomposed Granite
Granite
30m

100
 0
BH1 BH2 BH3

Fill
Fill Fill

Residual Soil Colluvium Residual Soil

Completely
Decomposed Completely
Completely Volcanic Tuff Decomposed
Decomposed Granite
Granite

Slightly
Decomposed Slightly
Slightly
Volcanic Tuff Decomposed
Decomposed
Granite
Granite
30m

101
 BH1+

Site

BH3+

BH2+ Fault

0 200 m

102
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ENVIRONMENTAL PROTECTION DEPARTMENT
Guidance Note for Contaminated Land Assessment and Remediation
https://www.epd.gov.hk/epd/sites/default/files/epd/gn_pdf/GN2014P243-2007c-
e.pdf
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After Fletcher 2004
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Laboratory Testing
Soil Testing

Background

The current international standards for soil testing are based on

classical soil mechanics, which hasbeen developed mainly for
sedimentary, transported and re-deposited soils.

Modification of these standards are needed for use on tropical

soils formed by in-situ weathering of rock.

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 Soil Testing

Geospec 3, which has been issued contains

thirty-two standard procedures for soil property
tests and seven standard procedures for soil shear
strength and compressibility tests.
Geospec 3 is continuously updated in e-format with
the latest version released on 29 August 2017.
https://www.cedd.gov.hk/eng/publications/geo/doc
/es3_2017.08.29.pdf

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???
Rock Tests

Determination of Point Load Strength of Rocks

ASTM D 5731-16
an index test intended to be used in rock classification or as an indirect
estimation of uniaxial compressive strength.

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Determination of Unconfined Uniaxial Compressive Strength

ASTM D2938-95 (replaced by D7012-14).

Unconfined compressive strength of rock is used in many design formulas

and is sometimes used as an index to select the appropriate excavation
technique.

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Determination of Direct Shear Strength of Discontinuities

ASTM D5607-16

Determination of shear strength of a rock discontinuities is an important aspect in

the design of structures such as rock slopes, dam foundations, underground
structures and other rock structures.

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 Constant
Normal Load

Gap
Encapsulating
5 mm min. material Water
0.2 L min.

Pinned
Shear Rock reaction
load Joint load

Encapsulating
material
Test horizon

Linear bearing

A schematic of an example shear box

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GI Reports

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 GI report - Basic information
– Location
– Geology
– Fieldwork (e.g. drillholes, trial pits, surface stripping, etc.)
– Field Testing (e.g. SPT, borehole televiewer, permeability test, etc.)
– Field Installation (e.g. standpipes, piezometers, etc)
– Logs, photos, plans
– Digital data
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Take a break