Site Investigation

Ir. Liew Shaw Shong

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IntroductionIntroduction

Scope Site InvestigationInformation on Hydrology, Meteorology, Environment, Natural Resources, Activities & Topography

Ground InvestigationInformation on Ground & Groundwater conditions

MonitoringTime dependent changes in ground movements, groundwater fluctuation & movements

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Purpose

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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).

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Geotechnical Engineering

Fluid Control Systemse.g. dams Underground

Geo-structurese.g. tunnel

Structural Support Systems

e.g. foundations

Ground Improvement

e.g. densification, remediation

Surface Geo-structurese.g. embankments,

landfills

Rock Mechanicsdeformation

failureseepage

Soil Mechanicsdeformation

failureseepage

Geologycomposition

genesisprocesseshydrology

HydrologySurface fluid flow

Structural Mechanicsdeformation

failuremember designContinuum

Mechanicselasticityplasticity

idealisationNumerical Analysisboundary element

finite differencediscrete element

finite element

Materialstypes

propertiesgeosynthetics

Geochemistrywaste

leachatesdurability

Site Explorationreconnaissance

drillingin-situ testing

laboratory testinggeophysics

Ground Movementsearthquakeliquefaction

sinkhole

Constructionpractice

experience

Mechanical Engineering

drillinginstrumentexcavation

Risk Managementobservation method

risk assessmentinstrumentation

Contract Lawspecification

Public Policycodes

standardlaws & compliance

Modified from Morgenstern (2000)

Fracture Mechanics

blastingquarry

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Genesis/Geology

Ground Profile

Appropriate Model

Ground Behaviour

Precedent,Empiricism,Experience,

Risk-management

Idealisation followed by evaluation. Conceptual or physical modelling

Analytical modelling

Lab/field testingObservation/measurement

Site investigationGround description

Burland’s Geotechnical

TriangleMorgenstern (2000)

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Source :http://www.sptimes.com/2004/04/16/Tampabay/At_site_of_collapse__.shtml 10

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Source :National Geographic (Jan 2008)12

Source :National Geographic (Jan 2008)13

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Captain, no worry! We are still far from

it.

Perceived Cost

Actual Cost

Consequence

How GI cost

How GI shall be done ?

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Codes & StandardsCodes & Standards

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Process Diagram of Ground Process Diagram of Ground InvestigationInvestigation

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Process Diagram of Ground Process Diagram of Ground InvestigationInvestigation

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Desk Study

Bid Document & Tender

Site Walk-over Survey

Identify Project Need

Scope of GI

Stage 1 of GIStage 1 of GI

““Without Site Investigation, Ground is a HazardWithout Site Investigation, Ground is a Hazard””19

Field Supervision

Work Certification

Sampling, In-situ Testing, Geophysical SurveyMonitoring

Laboratory Testing



Factual Data Compilation

Report Preparation

Interpretation



Desk StudyDesk StudyInformation for Desk Study :• Topographic Maps

• Geological Maps & Memoirs• Site Histories & Land Use• Aerial Photographs• Details of Adjacent Structures & Foundation• Adjacent & Nearby Ground Investigation

Project SitePipeline

sProject Site

AlluviumGranite

Jurong Formation

Pipeline

sProject Site

1999

PipelinesProject Site

1986

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Site Walkover SurveySite Walkover Survey

• Confirm the findings from Desk Study• Identify additional features & information not captured by Desk Study

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GI PlanningGI Planning

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Depth of Investigation

Stability Analysis

Foundation Design

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Common ProblemsCommon Problems

Incomplete Survey Information

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SpecificationSpecification

Objectives (study, design, forensic, construction)Type of investigation, mapping & field surveyVertical & lateral extent (termination depth)Sampling requirements (types, sampling locations & techniques)In-situ and laboratory testing requirements (standards)Measurement/monitoring requirements (instrument types & frequency)Skill level requirements in specialist works & interpretationReport format & data presentation

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SpecificationSpecification

Work schedule & GI resources planningPayments for services, liability, indemnity, insurance cover

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Boring/DrillingBoring/Drilling

MonitorinMonitoringg

InIn--situ situ TestinTestin

gg

RecovRecover er

SamplSamplee

- Subsurface stratification/profile- Material classification & variability- Laboratory tests

- Allow in-situ tests down hole (profiling)- Direct measurement of ground behaviours

- Allow monitoring instruments installed down hole

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Direct Method Direct Method –– Boring, Sampling, Boring, Sampling, InIn--situ & Laboratory Testingsitu & Laboratory TestingMedical Applications- Biopsy sampling

Geotechnical Applications- Boring, Trial Pitting & Sampling

• Thin-walled, Piston Sampler• Mazier Sampler• Block Sample

-In-situ Testing• SPT, MP, CPTu, VST, PMT, DMT,

PLT, • Permeability Test• 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)• Petrography & XRD

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Indirect Method Indirect Method –– Geophysical Geophysical SurveySurvey

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• Ground Penetration Radar• Seismic Method

Santamarina, J. C. (2008) - http://www.elitepco.com.tw/ISC3/images/Keynote-03-Santamarina.pdf33

Geophysical SurveyGeophysical Survey

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• Merits• Lateral variability (probing location)• Profiling (sampling & testing)• Sectioning (void detection)• Material classification• Engineering parameters (G0 & Gdynamic)

• Problems•Over sale/expectation•Misunderstanding between engineers, engineering geologists & geophysicists•Lack of communication•Wrong geophysical technique used•Interference/noice

SamplerSamplerSplit SpoonThin-WalledPiston SamplerMazier SamplerCore BarrelWire-line

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Sample Storage, Handling, Sample Storage, Handling, TransportationTransportation

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Sample PreparationSample Preparation

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SamplingSampling

• 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 AfterStress 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

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Clayton et al (1982)

Poor recoveryLonger rest period for sample swellingSlight over-samplingUse of sample retainer

Sample contamination

Sample DisturbanceSample Disturbance

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Sample Quality ClassificationSample Quality Classification

Sample Quality

Soil Properties

Classification

Moisture Content Density Strength Deformation Consolidatio

n

Class 1

Class 2

Class 3

Class 4

Class 545

InIn--situ Testssitu Tests

Piezocone (CPTu)

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InIn--Situ TestsSitu 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

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Applicability of InApplicability of In--situ Testssitu TestsTest K0 φ’ Cu σc E’/G Eu Gmax kSPT G C R G C G

CPT/CPTu G C GDMT G, C GPMT C G, R CPLT C G, R CVST C

Seismic G, C, RSBPMT G, C G C G, C

Falling/Rising Head Test

G

Constant Head Test

CPacker Test R

48Clayton , et al (1995) G = granular, C = cohesive, R


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Pressuremeter (PMT)

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Dilatometer (DMT)

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Instrumentation MonitoringInstrumentation Monitoring

• Inclinometer• Extensometer• Rod Settlement Gauge/Marker • Piezometer • Observation Well

Toward River

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Laboratory TestsLaboratory Tests

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Source : Life Style Magazine - EDGE 54

Ground CharacterisationGround CharacterisationFocus of Geological Model

Stratification

WeatheringHistorical Geological Processes

Hydrogeology

Geological Structures

Geo-morpholog

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Geological MappingGeological MappingMapping of :- Geological features (Structural settings)- Weathering profile- Outcrop exposure- Seepage conditions

- Geomorphology- Lithology- Stratification

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Ground CharacterisationGround CharacterisationFocus of Geotechnical Model

Subsurface Profile StiffnessStrength Permeability

Chemical Characteristi

cs

Material Type

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General Dilemma of GI IndustryGeneral Dilemma of GI Industry

• Lack of pride & appreciation from consultant/client in GI industry.

• Actions done is considered work done! Poor professionalism.

Financial survival problem due to competitive rates in uncontrolled environment (Cutting corner)

No appropriate time frame for proper work procedures (shoddy works)

Shifting of skilled expert to Oil & Gas or other attractive industries

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Poor Planning & InterpretationPoor Planning & InterpretationInadequate investigation coverage vertically & horizontallyWrong investigating toolsNo/wrong interpretationPoor investigating sequence

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Poor Site ImplementationPoor Site Implementation

Lack of level & coordinates of probing location

Sample storage, handling, transportation

Inappropriate equilibrium state in Observation Well & Piezometer

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Poor InPoor In--situ & Laboratory Resultssitu & Laboratory Results

Equipment calibration(Variation of pH Values)Improper sample preparationInadequate saturationInappropriate testing rateInadequate QA/QC in testing processesInherent sample disturbance before testing

Lack of calibrationWear & Tear ErrorsEquipment systematic error (rod friction, electronic signal drift, unsaturated porous tip)Defective sensorInappropriate testing procedures

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Poorly Maintained ToolsPoorly Maintained Tools

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OverOver--confidence in Geophysicsconfidence 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)- High capital costs in equipment & software investment

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Communication ProblemCommunication Problem

We are connecting the bridge deck at the same level successfully!

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Difficulties in Identification of Difficulties in Identification of Complex Geological SettingsComplex Geological Settings

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Difficulties in Identification of Difficulties in Identification of Complex Geological SettingsComplex Geological Settings

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Weathering ProfileWeathering Profile

Deviation of material classification between borehole and excavation (Claim issue –Soil or Rock ?)

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Complexity of Rock Mass Complexity of Rock Mass PropertiesPropertiesComplicated rock mass strength in slope & excavation designRequiring judgement (involving subjectivity)Information normally only available during construction a

ubu sm

⎥⎥⎦

⎤

⎢⎢⎣

⎡+⎟

⎟⎠

⎞⎜⎜⎝

⎛+=

σσ

σσσ'

'' 331

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Unexpected Blowout of Underground Unexpected Blowout of Underground GasGas

Gas pockets at 32m bglFlushing out of sand

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SupervisionSupervision

Assurance of work complianceCritical information is captured without missingTimely on-course instruction for sampling, in-situ testing & termination as most GI specifications are general in nature, but ground is unpredictable.Checking between field records and reported informationWork certification

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Future Trend Future Trend -- Electronic Data Electronic Data Collection, Transfer & ManagementCollection, 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• Spatial data analysis

73http://www.ags.org.uk/site/datatransfer/intro.cfm

ConclusionsConclusions

Nature of GI works & Geotechnical design (Uncertainties)Role of Geotechnical Engineer, Engineering Geologist & GeophysicistStages of GI works (Planning, Implementation, Interpretation & Report)SpecificationsMethodology of GI (Merits & Demerits)

Fieldworks (Direct/Indirect) + Geological MappingLaboratory tests

Common Problems & Future Trend

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ReferencesReferencesAnon (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.

European Group Subcommittee (1968). “Recommended method of Static and Dynamic Penetration Tests 1965”. Geotechnique, Vol. 1, No. 1.

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ReferencesReferencesFHWA (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

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Site Investigation