Site Investigation

Introduction

Introduction

Scope

ƒ

Site Investigation

_à

_{Information on Hydrology,}

Meteorology, Environment,

Natural Resources, Activities &

Topography

ƒ

Ground Investigation

à

Information on Ground &

Groundwater conditions

ƒ

Monitoring

à

Time dependent changes in

ground movements,

groundwater fluctuation &

movements

Introduction

Introduction

Purpose

Introduction

Introduction

Why doing GI? Why Geotechnical

Why doing GI? Why Geotechnical

Engineer? What Risk &

Engineer? What Risk &

Consequence

Consequence

Why doing GI?

It is regard as necessary, but not a

rewarding expense. (Uncertainty,

sufficiently accurate design options

for Cost & Benefit study)

Why Geotechnical Engineer?

Geotechnical engineer as an

underwriter for risk assessment.

What Risk in Ground & its

Consequence ?

Ground Variability & Geo-hazards.

Financial Viability & Cost Overrun

(Construction & Operation).

Geotechnical

Engineering

Fluid Control Systems

e.g. dams Underground Geo-structures e.g. tunnel Structural Support Systems e.g. foundations Ground Improvement e.g. densification, remediation Surface Geo-structures e.g. embankments, landfills Rock Mechanics deformation failure seepage Soil Mechanics deformation failure seepage Geology composition genesis processes hydrology Hydrology

Surface fluid flow

Structural Mechanics deformation failure member design Continuum Mechanics elasticity plasticity idealisation Numerical Analysis boundary element finite difference discrete element finite element Materials types properties geosynthetics Geochemistry waste leachates durability Site Exploration reconnaissance drilling in-situ testing laboratory testing geophysics Ground Movements earthquake liquefaction sinkhole Construction practice experience Mechanical Engineering drilling instrument excavation Risk Management observation method risk assessment instrumentation Contract Law specification Public Policy codes standard laws & compliance

Modified from Morgenstern (2000)

Fracture Mechanics

blasting quarry

Genesis/Geology

Ground

Profile

Appropriate

Model

Ground

Behaviour

Precedent,

Empiricism,

Experience,

Risk-management

Idealisation followed by evaluation. Lab/field testing Site investigation Ground description

Burland’s

Geotechnical

Triangle

Morgenstern (2000)

14

Captain, no worry!

We are still far from

it.

Perceive

d Cost

Actual

Cost

Consequence

ƒ

How GI cost

Codes & Standards

Codes & Standards

Process Diagram of Ground

Process Diagram of Ground

Investigation

Process Diagram of Ground

Process Diagram of Ground

Investigation

Investigation

Desk Study

Bid Document & Tender

Site Walk-over Survey

Identify Project Need

Scope of GI

Stage 1 of GI

Stage 1 of GI

“

Field Supervision

Work Certification

Sampling, In-situ

Testing, Geophysical

Survey

_Monitoring

Laboratory Testing

Stage 2 of GI

Stage 2 of GI

“

“

Without Site Investigation, Ground is a Hazard

Without Site Investigation, Ground is a Hazard

”

”

Factual Data Compilation

Report Preparation

Interpretation

Stage 3 of GI

Stage 3 of GI

“

Desk Study

Desk Study

Information for Desk Study :

•

Topographic Maps

•

Geological Maps & Memoirs

•

Site Histories & Land Use

•

Aerial Photographs

•

Details of Adjacent Structures &

Foundation

•

Adjacent & Nearby Ground Investigation

Proje ct Site Pipeline s Project Site Alluvium Granite Jurong Formation Pipeline

s

Site Walkover Survey

Site Walkover Survey

•

Confirm the findings from Desk

Study

•

Identify additional features &

information not captured by Desk

Study

GI Planning

GI Planning

Depth of Investigation

Stability Analysis

Common Problems

Common Problems

ƒ

Incomplete Survey Information

GI Planning

GI Planning

GI Planning

Specification

Specification

ƒ

Objectives (study, design, forensic, construction)

ƒ

Type of investigation, mapping & field survey

ƒ

Vertical & lateral extent (termination depth)

ƒ

Sampling requirements (types, sampling locations

& techniques)

ƒ

In-situ and laboratory testing requirements

(standards)

ƒ

Measurement/monitoring requirements (instrument

types & frequency)

ƒ

Skill level requirements in specialist works &

interpretation

Specification

Specification

ƒ

Work schedule & GI resources planning

ƒ

Payments for services, liability, indemnity,

insurance cover

Boring/Drilling

Boring/Drilling

In

In

-

-

situ

situ

Testin

Testin

g

g

Recov

Recov

er

er

Sampl

Sampl

e

e

- Subsurface stratification/profile

- Material classification & variability

- Laboratory tests

- Allow in-situ tests down hole (profiling)

- Direct measurement of ground

behaviours

Direct Method

Direct Method

–

–

Boring, Sampling,

Boring, Sampling,

In

In

-

-

situ & Laboratory Testing

situ & Laboratory Testing

Medical Applications

- Biopsy sampling

Geotechnical Applications

-

Boring, Trial Pitting & Sampling

• Thin-walled, Piston Sampler

• Mazier Sampler • Block Sample

-

In-situ Testing

• Field Density Test

-

Laboratory Testing

• Classification Test

• Compressibility Test (Oedometer/Swell)

• Strength Test (UU/UCT/CIU/DS)

• Permeability Test

• Compaction Test

• Chemical Test (pH, Cl, SO4, Redox, Organic Content)

Indirect Method

Indirect Method

–

–

Geophysical

Geophysical

Survey

Survey

Medical Applications

- X-ray, Computer Tomography & MRI

-

Ultra-sound

-

Geotechnical Applications

Geophysical Survey

- Electromagnetic Waves

(Permeability, Conductivity &

Permittivity)

- Mechanical Wave

(Attenuation, S-waves & P-waves)

•

Resistivity Method

Microgravity Method

•

Transient Electro-Magnetic

Method

Geophysical Survey

Geophysical Survey

34

•

Merits

•

Lateral variability (probing location)

•

Profiling (sampling & testing)

•

Sectioning (void detection)

•

Material classification

•

Engineering parameters (G

&

G

)

•

Problems

•

Over sale/expectation

•

Misunderstanding between

engineers, engineering

geologists & geophysicists

•

Lack of communication

•

Wrong geophysical technique

used

Sampler

Sampler

Split Spoon

Thin-Walled

Piston Sampler

Mazier Sampler

Core Barrel

Wire-line

Sampler

Sampler

Split Spoon

Thin-Walled

Piston Sampler

Mazier Sampler

Core Barrel

Wire-line

Sampler

Sampler

Split Spoon

Thin-Walled

Piston Sampler

Mazier Sampler

Core Barrel

Wire-line

Sampler

Sampler

Split Spoon

Thin-Walled

Piston Sampler

Mazier Sampler

Core Barrel

Wire-line

Sampler

Sampler

Split Spoon

Thin-Walled

Piston Sampler

Mazier Sampler

Core Barrel

Wire-line

Sampler

Sampler

Split Spoon

Thin-Walled

Piston Sampler

Mazier Sampler

Core Barrel

Wire-line

Sample Storage, Handling,

Sample Storage, Handling,

Transportation

Sample Preparation

Sample Preparation

Sampling

Sampling

•

Sample Sizes

•

Representative mass

(particle sizes, fabric,

fissures, joints)

•

Adequate quantity for

testing

•

Sample Disturbance

•

Stress conditions

•

Deformation behaviours

•

Moisture content & void

•

Chemical characteristics

Before

During

After

Stress relief

Stress relief

Stress relief

Swelling

Remoulding

Moisture

migration

Compaction

Displacement

Extrusion

Displacement

Shattering

Moisture loss

Base heave

Stone at

cutting shoe

Heating

Piping

Mixing or

segregation

Vibration

Caving

Poor recovery

Contamination

ƒ

Poor recovery

à

Longer rest period for sample

swelling

à

Slight over-sampling

à

Use of sample retainer

ƒ

Sample contamination

Sample Disturbance

Sample Disturbance

Sample Quality Classification

Sample Quality Classification

Sample

Quality

Soil Properties

Content Density Strength Deformation

Consolidatio n

Class 1

9

9

9

9

9

9

Class 2

9

9

9

2

2

2

Class 3

9

9

2

2

2

2

Class 4

9

2

2

2

2

2

2

2

2

2

2

2

In

In

-

-

situ Tests

situ Tests

Piezocone (CPTu)

In

In

-

-

Situ Tests

Situ Tests

•

BS1377 : Part 9

•

Suitable for materials with difficulty in sampling

•

Very soft & sensitive clay

•

Sandy & Gravelly soils

•

Weak & Fissured soils

•

Fractured rocks

•

Interpretation

•

Empirical

•

Semi-empirical

•

Analytical

Applicability of In

Applicability of In

-

-

situ Tests

situ Tests

Test

K

φ’

C

σ

E’/G

E

G

k

SPT

G

C

R

G

C

G

CPT/CPTu

G

C

G

DMT

G, C

G

PMT

C

G, R

C

PLT

C

G, R

C

VST

C

Seismic

G, C,

R

SBPMT

G, C

G

C

G, C

Falling/

Rising Head Test

G

Constant Head

Test

C

Packer Test

R

In

In

In

-

-

situ Tests

situ Tests

Pressuremeter (PMT)

In

In

-

-

situ Tests

situ Tests

Instrumentation Monitoring

Instrumentation Monitoring

•

Inclinometer

•

Extensometer

•

Rod Settlement Gauge/Marker

•

Piezometer

•

Observation Well

Toward River

Laboratory Tests

Ground Characterisation

Ground Characterisation

Focus of

Geological

Model

Stratificatio

n

Weathering

Historical

Geological

Processes

Hydrogeology

Geological

Structures

Geo-morpholog

Geological Mapping

Geological Mapping

Mapping of :

-

Geological features (Structural

settings)

-

Weathering profile

-

Outcrop exposure

-

Seepage conditions

-

Geomorphology

-

Lithology

- Stratification

Ground Characterisation

Ground Characterisation

Focus of

Geotechnical

Model

Subsurfa

ce Profile

Strength

Stiffness

Permeability

Chemical

Characteristi

Material

General Dilemma of GI Industry

General Dilemma of GI Industry

•

Lack of pride &

appreciation from

consultant/client in GI

industry.

•

Actions done is

considered work done!

Poor professionalism.

ƒ

Financial survival

problem due to

competitive rates in

uncontrolled environment

(Cutting corner)

ƒ

No appropriate time

frame for proper work

procedures (shoddy

works)

ƒ

Shifting of skilled expert

to Oil & Gas or other

attractive industries

Poor Planning & Interpretation

Poor Planning & Interpretation

ƒ

Inadequate investigation

coverage vertically &

horizontally

ƒ

Wrong investigating tools

ƒ

No/wrong interpretation

Poor Site Implementation

Poor Site Implementation

ƒ

Lack of level & coordinates of probing

location

ƒ

Sample storage, handling,

transportation

ƒ

Inappropriate equilibrium state in

Observation Well & Piezometer

Poor In

Poor In

-

-

situ & Laboratory Results

situ & Laboratory Results

ƒ

Equipment calibration

(Variation of pH Values)

ƒ

Improper sample

preparation

ƒ

Inadequate saturation

ƒ

Inappropriate testing rate

ƒ

Inadequate QA/QC in

testing processes

ƒ

Inherent sample

disturbance before

testing

ƒ

Lack of calibration

ƒ

Wear & Tear Errors

ƒ

Equipment systematic

error (rod friction,

electronic signal drift,

unsaturated porous tip)

ƒ

Defective sensor

ƒ

Inappropriate testing

procedures

Poorly Maintained Tools

Poorly Maintained Tools

Over

Over

-

-

confidence in Geophysics

confidence in Geophysics

-

We detect everything, but indentify almost nothing

(Rich but Complex).

-

Geophysical data is rich in content, but very complex in

nature.

-

Not a unique solution in tomographic reconstruction

(Indirect method)

-

Poor remuneration to land geophysicist as compared to O&G

-

Poor investigation specification

-

Lack of good interpretative skill (human capital)

Communication Problem

Communication Problem

We are connecting the bridge

deck at the same level

successfully!

Difficulties in Identification of

Difficulties in Identification of

Complex Geological Settings

Difficulties in Identification of

Difficulties in Identification of

Complex Geological Settings

Complex Geological Settings

Weathering Profile

Weathering Profile

ƒ

Deviation of material classification between

borehole and excavation

(Claim issue –

Complexity of Rock Mass

Complexity of Rock Mass

Properties

Properties

ƒ

Complicated rock mass strength in slope & excavation

design

ƒ

Requiring judgement (involving subjectivity)

ƒ

Information normally only available during construction

u b u

m

s

⎥

⎥

⎦

⎤

⎢

⎢

⎣

⎡

+

⎟

⎟

⎠

⎞

⎜

⎜

⎝

⎛

+

=

σ

σ

σ

σ

σ

'

'

'

Unexpected Blowout of Underground

Unexpected Blowout of Underground

Gas

Gas

ƒ

Gas pockets at 32m

bgl

Supervision

Supervision

ƒ

Assurance of work compliance

ƒ

Critical information is captured without missing

ƒ

Timely on-course instruction for sampling,

in-situ testing & termination as most GI

specifications are general in nature, but ground

is unpredictable.

ƒ

Checking between field records and reported

information

ƒ

Work certification

Future Trend

Future Trend

-

-

Electronic Data

Electronic Data

Collection, Transfer & Management

Collection, Transfer & Management

•

AGS data transfer format &

AGS-M format (monitoring data)

•

First Edition in 1992,

AGS(1992)

•

Second Edition in 1994,

AGS(1994)

•

Third Edition in 1999

•

Advantages :

•

Efficient & Simplicity

•

Minimised human error

•

GI & Monitoring Data

Management System

•

Record keeping

Conclusions

Conclusions

ƒ

Nature of GI works & Geotechnical design

(

Uncertainties

)

ƒ

Role of Geotechnical Engineer, Engineering

Geologist & Geophysicist

ƒ

Stages of GI works (

Planning, Implementation,

Interpretation & Report

)

ƒ

Specifications

ƒ

Methodology of GI (Merits & Demerits)

à

Fieldworks (Direct/Indirect) + Geological Mapping

à

Laboratory tests

ƒ

Common Problems & Future Trend

References

References

Anon (1999). “Definition of Geotechnical Engineering”. Ground Engineering, Vol. 32, No. 11, pp. 39.

BSI (1981). “Code of Practice for Site Investigation, BS 5930”. British Standards Institution, London.

BSI (1981). “Code of Practice for Earthworks, BS 6031”. British Standards Institution, London.

BSI (1986). “Code Practice for Foundation, BS8004”. British Standards Institution, London.

BSI (1990). “British Standard Methods of Test for Soils for Civil Engineering Purposes, BS 1377”. British Standards Institution, London.

Clayton, C. R. I., Matthews, M. C. & Simons, N. E. (1995). “Site Investigation”, Blackwell Science, 2nd edition.

Gue, S. S. & Tan, Y. C. (2005), “Planning of Subsurface Investigation and Interpretation of Test Results for Geotechnical Design”, Sabah Branch, IEM.

Liew, S. S. (2005). “Common Problems of Site Investigation Works in a Linear Infrastructure Project”, IEM-MSIA Seminar on Site Investigation Practice, 9 August 2005, Armada Hotel, Kuala Lumpur.

References

References

FHWA (2002), “Subsurface Investigations — Geotechnical Site Characterization”. NHI Course No. 132031. Publication No. FHWA NHI-01-031

GCO (1984). “Geotechnical Manual for Slopes”. Geotechnical Control Office, Hong Kong

GCO (1980). “Geoguide 2 : Guide to Site Investigation, Geotechnical Control Office, Hong Kong

Gue, S. S. (1985). “Geotechnical Assessment for Hillside Development”. Proceedings of the Symposium on Hillside Development; Engineering Practice and Local By-Laws, The Institution of Engineers,

Malaysia.

Head, K. H. (1984). “Manual of Soil Laboratory testing”.

Morgenstern, N. R. (2000). “Common Ground”. GeoEng2000, Vol. 1, pp. 1-20.

Neoh, C. A. (1995). “Guidelines for Planning Scope of Site Investigation for Road Projects”. Public Works Department, Malaysia

Ooi, T.A. & Ting, W.H. (1975). “The Use of a Light Dynamic Cone Penetrometer in Malaysia”. Proceeding of 4th Southeast Asian Conference on Soil Engineering, Kuala Lumpur, pp. 3-62, 3-79

Ting, W.H. (1972). “Subsurface Exploration and Foundation Problems in the Kuala Lumpur Area”. Journal of Institution of Engineers, Malaysia, Vol. 13, pp. 19-25

Santamarina, J. C. (2008). “The Geophysical Properties of Soils”, 3rd Int. Conf. on Site Characterisation, Keynote Lecture No. 3, Taiwan.

Site Investigation Steering Group, “Without Site Investigation, Ground is a Hazard”, Part 1, Site Investigation in Construction Thomas Telford Ltd