geotechnical instrumentation by ir. liew shaw … · geotechnical instrumentation workshop menara...
TRANSCRIPT
10/22/2010
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Company
LOGO
By Ir. Liew Shaw Shong
GEOTECHNICAL INSTRUMENTATION WORKSHOP
Menara PJD, JKR Headquarters, 26-27 October 2010
Course Outline
Planning, Specification & Contractual Arrangement
Site Monitoring
Data Processing / Analysis, Interpretation & Actions
Common Problems, Applications& Lesson Leant from Case Study
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2
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Geotechnical Engineer
岩土工程师
大地工程師
� Geotechnical engineer in Malaysia is ambiguously regarded as “Geologist” in the public perception.
� Geotechnical engineer is a qualified civil engineer registered with Board of Engineers Malaysia as either graduate engineer or professional engineer having relevant and competent experience in geotechnical works
� ability to plan ground investigation & characterise ground conditions for engineering processes
� identify & assess the potential geo-hazards and the possible ground borne interaction to proposed structures
� offer feasible engineering design solutions to ensure safety & satisfactory performance of the end product of the engineering works including its surrounding 3
Civil Engineer
Geotechnical Engineer
� Why Geotechnical Engineer?� Geotechnical engineer as an
underwriter for risk assessment.
� GI as tools for Geotechnical Engineer
� It is regard as necessary, but not a rewarding expense. (Uncertainty, sufficiently accurate design options for Cost & Benefit study)
� What Risk in Ground & its Consequence ?
� Ground Variability & Geo-hazards.� Financial Viability & Cost Overrun
(Construction & Operation).
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Why appoint Geotechnical Engineer?
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5
Risk Evaluation with Cost-
Benefit Analysis
Risk Mitigation (Pro-active)
Risk Reduction (Defensive)
Risk Avoidance
Risk Assessment
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Geotechnical Engineering
Fluid Control Systemse.g. dams
Underground Geo-structures
e.g. tunnel
Structural Support Systems
e.g. foundations
Ground Improvemente.g. densification,
remediation
Surface Geo-structurese.g. embankments, landfills
Rock Mechanicsdeformation
failureseepage
Soil Mechanicsdeformation
failureseepage
Geologycomposition
genesisprocesseshydrology
HydrologySurface fluid flow
Structural Mechanicsdeformation
failuremember design
Continuum Mechanicselasticityplasticity
idealisation
Numerical Analysisboundary element
finite differencediscrete element
finite element
Materialstypes
propertiesgeosynthetics
Geochemistrywaste
leachatesdurability
Site Explorationreconnaissance
drillingin-situ testing
laboratory testinggeophysics
Ground Movementsearthquakeliquefaction
sinkhole
Constructionpractice
experience
Mechanical Engineeringdrilling
instrumentexcavation
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 descriptionBurland’s
Geotechnical Triangle
Morgenstern (2000)
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Engineering Judgement
� Definition : The operation of the mind, involving “comparison” and “discrimination” by which knowledge of values and relations is mentally formulated. (Webster’s New Collegiate Dictionary)
� Recognition : Engineering judgement as an acceptable engineering practice
Engineering Judgement
ExperienceDirectly or
indirectly from others
KnowledgeFamiliarity gained from Experience
JudgementKnowledge of all
kinds & from many different sources
Process of Developing Judgement
Judgement
Knowledge
Experience
Theoretical Concepts
Experimental Methods
Measurements
Observations
Past Experience
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Soil-Structure Interactions
Time Dependent Behaviours
Groundwater Related
Problems
Foundations
Earthworks
Scope
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Work Scope of Geotechnical Engineer
Natural geologic materials of inherentlyvariable nature do not necessarily follow well-defined natural laws, hence renderingprediction in high uncertainty.
Potential Scope of Geotechnical Engineering (modifi ed from Atkinson, 2006) 12
Natural Terrain
Instability
Cut Slope Instability
Slope Strengthening
Fill Slope Instability
Retaining Structure
Reservoir Dam
Basement Excavation
Underground Space &
Foundation
Embankment
Tunnel
Environmental Landfill
PVD Ground Treatment
with Preloading
Ground Treatment with Stone Columns
Maritime Structures
ReclamationDredging
Stability & Erosion
Protection
Offshore Structures
Work Scope of Geotechnical Engineer
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WHY DO WE NEED INSTRUMENTATION??
It is a useful tool to supplement what we can not identify trend of behaviours & quantify the changes of the crucial parameters affecting the bahaviours in the observation.
Why Instrumentation?
Theory .vs. Observation
Sir Isaac Newton – Law of Gravity by observation
Observation with
Measurements
Theoretical Development
Albert Einstein - General relativity'spredictions have been confirmed in allobservations and experiments to date.
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Benefits of Instrumentation
Design Verification & Optimisation
Construction & Operational Safety
Cost & Time Saving
If you can not get high quality and reliable data, then better don’t initiate any instrumentation scheme because it will create more problems than being advantageous.
Pitfalls of Instrumentation
Design Rectification
Overly Caution of SafetyPotential Legal Evidence
Realistic Construction Cost & Time
In some cases, instrumentation results may reveal the shortcomings or negligence in the design of the project designer and also those by the work contractor.
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Purpose & Objectives
Maintenance Monitoring- Long Term Performance- Necessary Maintenance Action- Early Warning System
Construction Monitoring- Safety- Observation Method- Construction Control - Legal Protection- Quantity Measurement- Public Relation
Design Verification- Failure mechanism & Capacity- Serviceability- Reveal unknowns- Pile Load Test- Pullout Test-Trial Embankment
Design Construction Operation
Forensic Investigation
Failure mechanism, Serviceability, Contributory & T riggering Factors
Stakeholders
Project Objectives
ProjectOwner
InstrumentSpecialist
DesignConsultant
ConstructionContractor
InsuranceCompany
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Responsibility
ResponseActions
InstrumentsSelection
InstrumentInstallation Data
Collection
Calibration&
InterpretData
Cycle related to high quality Instrumentation
Scheme
Responsibility
Instrument Procurement
• Instrument (hardware & software)• Factory calibration
Field Instrumentation
Service
• Acceptance tests• Instrument installation• Establish baseline reading• Maintaining & calibrating instruments regularly• Data collection, processing & presentation
Interpretation & Response
Actions
• Interpret & report data• Review need for response actions & instruction• Timely implementation of response actions
Instrumentation Specialist
Project DesignerInstrumentation Specialist
Project DesignerWork Contractor
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Parameters to be Monitored
Types of Measurement
GroundDeformation
Ground/StructuralStresses
WaterPressure Thermal
Vibration/Flow
Planning Cycle
ControllingMechanisms
DefineProject
Conditions
ResponseActions
Measurement.vs.
PredictionPurpose &Parameters
to be measured
Questionsto be answered
Every instrument shall be placed at the site to answer specific question. If no question, then no instrument.
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Project Conditions
� Construction Control : modify or improve the initial construction sequence or/and method.
� Remedy : strengthen the stability, reduce the negative impacts, repair the damage or distresses
� Notice : serving notice to project owner, insurance, neighbouring owners, local authorities
Questions to be answered
� Any Questions related to Performance of the Concerned System• Deformation of Ground or Structures• Stress or Strain in Ground or Structure• Water Pressure Distribution, Flow and
Changes• Thermal, Vibration, Tidal Effects• Location and magnitude of changes
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What does instrument measure & response?
Effects
Causes
• Measurement can be either performed on the changes of CAUSES (difficult to pick up the changes) or EFFECTS (usually too late for response actions).
• Most instruments provide point measurement with dependence on localisedcharacteristics, hence may not represent the problem in larger scale, unless large number of point measurement instruments are installed.
Controlling Mechanisms
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Measurement .vs. Prediction
GreenNo action
AmberCautionary Measures
RedTimely
Contingency Action
Hazard Warning Level
Measurement
Prediction
Analysis
Don’t forget to apply Engineering
Judgement
Response Actions
� Construction Control : modify or improve the initial construction sequence or/and method.
� Remedy : strengthen the stability, reduce the negative impacts, repair the damage or distresses
� Notice : serving notice to project owner, insurance, neighbouring owners, local authorities
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Dilemma of Instrumentation
1 : Doc, can you guarantee I have 100% fix of all my
problems?
2 : Well, do you want me to open up
everything, big or small one, to check
for fixing.
3 : Doc, his credit card limit is up to RM50,000 only.
Specification
Clear Concise Complete Correct
Over-specified-High price-Inadequate budget with expectation of omission of requirements-Inexperienced site staffing
-PrescriptiveOwner accept liability, but better control
-PerformanceInnovation, no bias, clear liability, competitive, but difficult to evaluate
Project-specific-Measurement range-Duration of service
Under Owner-Sufficient baseline data-Avoid price slaughter in subcontracting
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Contractual Arrangement
Project Owner
Consultant (PMC)
Site Supervision Team
Instrumentation Specialist Firm
Main Contractor
Subcontractor
Construction Works
Project Owner
Consultant (PMC)
Site Supervision Team
Main Contractor
Instrumentation Specialist FirmSubcontractor
Construction Works
Project Owner
Main Contractor (PM)
Consultant Site Supervision Team
Instrumentation Specialist Firm
Subcontractor
Construction Works
Independence : Good Independence : Fair Independence : PoorData Quality : Good Data Quality : Possibly Fair Data Quality : Possibly Poor
Problem : No liability for Contractor
Problem : Low bid tender Problem : Low bid tender
Advice : Nominate SpecialistAdvice : Nominate Specialist
Procurement Approach
� Professional Service� Lowest Bid Tender� Independence
We’re underfunded, but we manage!
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Good Practices
� Instrument Life-Cycle Costs : Calibration, installation, taking readings, maintenance, data management & interpretation, and decommissioning.
� Partnership to Instrument Manufacturers/Suppliers
Good Practices
� Good QA/QC of Personnel Training, Equipments, Data Management
� Dedicated Team & Equipment for Project
� Measures of Instrument Protection
� Duplicate Instruments for Data Redundancy
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Course Outline
Planning, Specification & Contractual Arrangement
Site Monitoring
Data Processing / Analysis, Interpretation & Actions
Common Problems, Applications& Lesson Leant from Case Study
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2
3
4
MeasurementUncertainty & Reliability
Accuracy Precision
Sensitivity Resolution
Conformance
Linearity Hysteresis
Error Noise
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Conformance
• Good conformance of instrument and installation procedures are necessary for measurement of good accuracy.• Beware of any changes of properties related to parameters to be measured due to presence of instrument
Accuracy & Precision
Accuracy High High Low Low
Precision High Low High Low
Acceptance Good Fair Systematic Error Bad
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Measurement Deviation
� Resolution : the degree to which the smallest change it can detect in the quantity that it is measuring.
� Sensitivity : the smallest absolute amount of change that can be detected by a measurement, usually defined as the ratio between output signal and measured property
� Linearity : The amount of error change throughout an instrument's measurement range. Linearity is also the amount of deviation from an instrument's ideal straight-line performance.
� Hysteresis : an error caused by when the measured property reverses direction, but there is some finite lag in time for the sensor to respond, creating a different offset error in one direction than in the other
� Noise : Random measurement variations by external factors
Linearity & Hysteresis
Non Linearity Hysteresis
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Types of Errors & Corrective Measures
Type of Error Sources Corrective Actions
Gross Error Human mistakes Care, checking & training
Systematic Error Calibration, hysteresis & non-linearity
Periodic recalibration
Conformance Error Instrument design & installation Appropriate instrument, improveinstallation procedures
Environmental Error Weather, temperature, vibration & corrosion
Apply correction with recorded environmental changes & conditioning instrument to ambient environment
Observation Error Variation between observers Training & automised data acquisition
Sampling Error Inherent variability & samplingtechnique
Sufficient instruments
Random Error Noise, friction & environmental effect
Statistical analysis on multiple readings
Course Outline
Planning, Specification & Contractual Arrangement
Site Monitoring
Data Processing / Analysis, Interpretation & Actions
Common Problems, Applications& Lesson Leant from Case Study
1
2
3
4
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Parameters to be Measured
� Deformation/Movement� Inclinometer� Extensometer� Ground Movement Marker� Tiltmeter� Crackmeter
� Water/Earth Pressure� Piezometer, Observation Well� Earth Pressure Cell
Parameters & Measurement
� Load/Stress/Strain � Strain Gauges� Load Cell
� Thermal� Thermal Coupler
� Flow� V-Notch Gauge
� Vibration� Accelerometer
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Inclinometer
� Inclinometer
L
θθθθ
L××××Sin θθθθ
A+A-
+θ+θ+θ+θ
A-A+
−−−−θθθθ
d1
d1 + d2
θθθθ1111
θθθθ2222
θθθθ3333
d1 + d2 + d3
+δ+δ+δ+δ
−−−−δδδδ
A+ Reading : +(+(+(+(θ+δθ+δθ+δθ+δ))))
A- Reading : −−−−(θ(θ(θ(θ−−−−δ)δ)δ)δ)
Reading :
{+(+(+(+(θ+δθ+δθ+δθ+δ) ) ) ) −−−− [[[[−−−−(θ(θ(θ(θ−−−−δ)]}/2 = θ δ)]}/2 = θ δ)]}/2 = θ δ)]}/2 = θ
Checksum Review :
{+(+(+(+(θ+δθ+δθ+δθ+δ) + [) + [) + [) + [−−−−(θ(θ(θ(θ−−−−δ)]}/2 = δ δ)]}/2 = δ δ)]}/2 = δ δ)]}/2 = δ
Inclinometer
Random Errors
Systematic Errors
Total Error
Sensor Bias Shift,
Sensitivity Drift &
Rotation
SensorPositioning,
Casing inclination & Curvature
Systematic Error
Poor Installation
Sensor Precision
Random Error
Unpredictable & Uncorrectable
Predictable & Correctable
Systematic errors can accumulate upward in the cumulative displacement at ground surface (apparent cumulative displacement ).
Total Error = εRandom ×××× √√√√(No. of Readings) + εSystematic ×××× (No. of Readings)
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Inclinometer
Bias Shift Sensitivity Drift
Rotation Error
Depth Positioning
Reading, y
b = Bias Shift
k Sin x
y = k Sin x + b
Sin x
k = Sensitivity Drift (Drift in Pre-amplifier)
Solutions : Factory calibration and repair of probe is needed.
Misalignment of SensorCurvature in Casing, Vertical Probe Placing, Cable Stretching, Ground Settlement
Easy to detect & correct
Easy to detect & correct
Rare, difficult to detect, but easy to correct
Difficult to detect & correct (time consuming & tedious)
αA0B0
Rotation Error Angle
Inclinometer
Err
or
Err
or
Err
or
Identification & Correction of Bias Shift Error
Identification & Correction of Rotation Error
Change Deflection Change Deflection
No Correction Deflection, A-Axis
Casing Profile, B-Axis (Cross Axis Inclination
CorrectedDeflection, A-Axis
No Correction With Zero Shift Correction
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Inclinometer
� Spiral Probe� Twisted casings lead to incorrect magnitude of
movement in the A and B directions.� Application :
� To check orientation of the inclinometer grooves for necessary correction for direction of resultant movement.
� Readings show movements in unlikely direction
� Check installation quality� Deep casing installation
ααααA R =d/Cos αααα
αααα
If αααα = 10°°°°,R =A/Cos αααα =1.015A
B
Inclinometer
� Error Detection & Correction : � Double data redundancy with readings
taken in diametrical direction� 3 to 6m bottom of casing into firm strata
for good fixity to provide calibration data
� Deeper readings have highest potential systematic errors : (a) Sensor warming up, (b) Steepest borehole inclination, (c) Further distance from top reference
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Inclinometer
� Tolerance : Variation of Checksum < 5 to 10 units of Mean Checksum
� Correction : � If the large variation is localised to one
depth, correction can be performed based on mean of other checksum.
� If the large variation spreads over the entire dataset, it is better to retake the readings.
Inclinometer
� Inclinometer (Vertical)
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Inclinometer
� Horizontal Profiler
0 2 4 6 8 10 12 14 16 18 20Distance From Starting End of Inclinometer (m)
-26
-24
-22
-20
-18
-16
-14
-12
-10
-8
-6
-4
-2
0
Set
tlem
ent (
mm
)
Water Load 452T-19/06/20011530T-20/06/20011630T-21/06/20011756T-22/06/20011894T-23/06/20012007T-24/06/20012087T-25/06/20012295T-26/06/20012521T-27/06/20012721T-28/06/20012910T-29/06/20012960T-29/06/20012947T-30/06/20012922T-01/07/20011517T-02/07/2001
0 2 4 6 8 10 12 14 16 18 20Distance From Staring End of Inclinometer (m)
-160
-140
-120
-100
-80
-60
-40
-20
0
Set
tlem
ent
(mm
) Measured Raft Deflection Profileat Water Load of 2521Ton
Predicted Raft Deflection Profile
at Water Load of 2500Ton
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20Distance From Staring End of Inclinometer (m)
250
200
150
100
50
0
-50
-100
-150
-200
-250
Ben
ding
Mom
ent (
kNm
/m w
idth
)
Ho
ggin
gS
agg
ing
G1(24m)
G2(24m)
G3(30m)
G4(30m)
G5(36m)
G6(36m)
G7(36m)
G8(36m)
G9(36m)
G10(30m)
G11(30m)
G12(24m)
G13(24m)
Inclinometer
� Horizontal Profiler
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Data Evaluation
� Type of Ground Movement
Deflection Deflection
Developed Shear Zone with Drastic Movement Profile
Creeping Slope with Continuous Movement Profile
Data Presentation
� Good Practice :� Use of exaggerated horizontal scale shall
be avoided because “errors” are magnified & could be misinterpreted.
� Change plot (incremental deformation) is useful to emphasize the location of deformation zone.
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Case Studies
� Demo 1 – Open Cut Excavations using Jack-In Pipe Anchorage & Soil Nail Anchorage
� Demo 2 – 8 Cases on Landslides� Demo 3 – Piling Foundation� Demo 4 – Reinforced Soil Wall with Stone
Columns Improvement� Demo 5 – Dewatering� Demo 6 – Dam
Course Outline
Planning, Specification & Contractual Arrangement
Site Monitoring
Data Processing / Analysis, Interpretation & Actions
Common Problems, Applications& Lesson Leant from Case Study
1
2
3
4
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Myths in Instrumentation
� Myth No.1 : Instrumentation can prevent bad thing from occurring.
� Myth No. 2 : Maintenance free instruments are possible.
� Myth No. 3 : Geotechnical engineer is not needed to review the instrumentation results if threshold and action plan are available (traffic light system).
� Myth No. 4 : Instrumentation does not require the input from instrumentation specialist.
Myths in Instrumentation
� Myth No. 5 : Instrumentation can replace engineering judgement. Everything is fine if instrumentation is in place.
� Myth No.6 : More instruments and data are better.
� Myth No. 7 : Instrumentation is costly investment, hence is unnecessary if the design is good.
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Common Problems
� Instrument : Selection of appropriate instrument fit for the purpose.
� Contract Arrangement : Interest party for high quality instrumentation data.
� Data Quality : Poor quality data will neither reveal the truth of engineering behavioursnor give correct warning.
� Data Management : Keeping raw data is essential for future data reprocessing with new interpretative objectives
Common Problems
� Data Interpretation : Screening & filtering of problematic data or uninvited events/factors for a distilled content are deliberately needed.
� Data Presentation : Data presentation without connection to records of activities at site is a discounted information for decision making.
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Common Problems
� Review : Timely review is important to capture indication of distress development & need for instrument maintenance/checking for proper functioning.
� Loss of Feel : Sometimes readings given to person who is not taking care of the instruments has no clue to slight variation of the readings, but possible an important indication of adverse effect. (You will not know your baby if you did not take care of him/her.)
� Threshold Limits : It is not easy to set a accurate set of threshold limits for multiple parameters controlling the behaviours.
� Action : Timely implementation of actions asidentified from interpreting instrumentation results.
Advices
� Paradox :• Appearance of apparently unmotivated
change are often the first sign of distress• Observations of overall phenomenon
become more relevant than “spot” occurrence.
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Applications
� Observation Method (e.g. NATM in Tunnel)
Natural Terrain
Instability
Cut Slope Instability
Slope Strengthening
Fill Slope Instability
Retaining Structure
Reservoir Dam
Basement Excavation
Underground Space &
Foundation
Embankment
Tunnel
Environmental Landfill
PVD Ground Treatment
with Preloading
Ground Treatment with Stone Columns
Maritime Structures
ReclamationDredging
Stability & Erosion
Protection
Offshore Structures
Earthfill/Clay Core RockfillDam
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Concrete Dam
Tunnel & Underground Excavation
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Strutting & Excavation
Design Verification Testing
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Case Studies
� Demo 1 – Open Cut Excavations using Jack-In Pipe Anchorage & Soil Nail Anchorage
� Demo 2 – 8 Cases on Landslides� Demo 3 – Piling Foundation� Demo 4 – Reinforced Soil Wall with Stone
Columns Improvement� Demo 5 – Dewatering� Demo 6 – Dam
References
� Sources :� Dunnicliff, J. (1988), ”Geotechnical Instrumentation for Monitoring Field Performance”. Wiley-Interscience Publication.� Geotechical Intrumentation News (http://www.bitech.ca/news.htm)� Liew, S.S. (2010), "Lessons Learned from Case Histories", JKR Sabah One-Day Short Course on Slope Engineering, Promenade Hotel,
Kota Kinabalu, Sabah, 30 June 2010� Liew,S.S. (2010), “Dam Safety Monitoring and Surveillance in Malaysia”, Conference on ASIAWATER 2010, jointly organized by The
Malaysian Water Association (MWA), 6th – 8th April 2010� Liew, S.S.; Lim, Wei & Lau, L.S. (2010), “Investigation of Soil Nailed Slope Distress at Fill Ground & Remedial Solutions”, The
17th Southeast Asian Geotechnical Conference, Taipei, Taiwan, 10 to 13 May 2010 Liew, S.S.; Lee, S.T. & Koo, K.S. (2010), “Failure Investigation of Piled Reinforcement Soil Wall & Excessive Movements of Piled Embankment at Soft Ground, Malaysia”, The 17th Southeast Asian Geotechnical Conference, Taipei, Taiwan, 10 to 13 May 2010
� Liew, S.S.; Ting, D.I. & Low, Y.H. (2010), “Piling Foundation Design & Construction Problems of Tank Farm in Reclaimed Land over Untreated Soft Marine Clay in Malaysia”, The 17th Southeast Asian Geotechnical Conference, Taipei, Taiwan, 10 to 13 May 2010
� Liew, S.S. (2009), “Role of Geotechnical Engineer in Civil Engineering Works in Malaysia”, CIE-IEM Joint Seminar on Geotechnical Engineering, Yilan, Taiwan, 26 to 27 August 2009
� Liew, S.S. & Khoo C.M. (2008), "Lessons Learned from Two Investigation Cases of Ground Distresses Due to Deep Excavation in Filled Ground", 6th Int'l Conf. on Case Histories in Geotechnical Engineering, 11-16 Aug 2008 , Arlington, Virginia, United States.
� Liew, SS (2008), "Case Studies of Support of Open Excavations and Distressed Retaining Walls in Malaysia" Seminar on "Deep Excavation and Retaining Walls", Jointly organised by IEM-HKIE at Tropicana Golf & Country Resort, Petaling Jaya, Malaysia, 24 March 2008.
� Liew S.S. & Khoo C.M. (2007),"Performance of Soil Nail Stabilisation Works for a 14.5m Deep Excavation at Uncontrolled Fill Ground", Proc. 16th Southeast Asian Geotechnical Conferences, Malaysia.
� Liew S. S. & Tan S. K. (2007), "Performance of Reinforced Soil Wall Supported on Stone Columns", Proc. 16th Southeast Asian Geotechnical Conferences, Malaysia.
� Liew S.S. & Khoo C. M. (2006),"Design and Construction of Soil Nail Strengthening Work over Uncontrolled Fill for a 14.5m Deep Excavation", 10th International Conference on Piling and Deep Foundations, 31 May - 2 Jun 2006, Amsterdam, The Netherlands
� Liew S.S. & Liong C.H. (2006),"Two Case Studies on Soil Nailed Slope Failures", Internationals Conference on slope, 7 - 8 August 2006, Kuala Lumpur
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References
� Sources :� Liew, S. S., Liong, C. H. & Low, C. L., (2004), “Four Landslide Investigations in Malaysia”, 15th SEAGC, Bangkok, 22 - 26
November 2004. � Liew, S. S. & Choo, E. L., (2004), “Bending Moment Interpretation of Structural Element with Measured Deflection Profile”,
Malaysian Geotechnical Conference, 16-18 March, 2004, Sheraton Subang, Petaling Jaya, Malaysia. � Liew, S. S., Kowng, Y. W. & Gan, S. J., (2004), “Interpretations of Instrumented Bored Piles in Kenny Hill Formation”,
Malaysian Geotechnical Conference, 16-18 March, 2004, Sheraton Subang, Petaling Jaya, Malaysia.� Liew, S. S., Gue, S. S. & Liong, C. H., (2003), “Geotechnical Investigation and Monitoring Results of a Landslide Failure at
Southern Peninsula Malaysia (Part 1: Investigating Causes of Failure)”, International Conference on Slope Engineering, Hong Kong, 8-10 Dec 2003.
� Liew, S. S., Gue, S. S. & Liong, C. H., (2003), “Geotechnical Investigation and Monitoring Results of a Landslide Failure at Southern Peninsula Malaysia (Part 2: Back Analyses of Shear Strength and Remedial Works)”, International Conference on Slope Engineering, Hong Kong, 8-10 Dec 2003.
� Liew, S. S. , Tan, Y. C., Ng, H. B. & Lee, P.T., (2003), “New Approach of using Jacked Anchors as Reinforcements in Soil Stabilisation Works for a Cut-And-Cover Tunnel with 17m Deep Excavation”, International Conference on Foundation, Dundee, Scotland, 2-5 Sep 2003.
� Liew, S. S., Gue, S. S. & Tan, Y. C. (2002), "Design and Instrumentation Results of A Reinforcement Concrete Piled Raft Supporting 2500 Ton Oil Storage Tank on Very Soft Alluvium Deposits", Ninth International Conference on Piling and Deep Foundations, Nice, 3 - 5 June, 2002
� Liew, S. S. (2002), "Pile Design with Negative Skin Friction" Course Lecture for Geotechnical Engineering at Puteri Pan Pacific Hotel, Johor Bahru
� Liew, S. S. & Gue, S. S. (2001), “Massive Creep Movements of Post-Glacial Deposits in Kundasang Areas”, GSM-IEM Forum : Engineering Geology & Geotechnics of Slopes, Kuala Lumpur
� Liew, S.S.; Gue, S. S., & Tan, Y. C. (1999), “Instrumentation Results on Negative Downdrag Force of Abutment Piles Underneath the Reinforced Earth Wall Embankment”, 5th Int.. Symp. on Field Measurements in Geomechanics., Singapore.
� Machan, G. & Bennet, V. G. (2008), “Use of Inclinometers for Geotechnical Instrumentation on Tranportation Projects – State of the Practice”, Transportation Research Board
� Mikkelsen, P. K. (2003), “Advances in Inclinometer Data Analysis”, Symposium on Field Measurements in Geotechnics(FMGM) 2003, Oslo, Norway
Thank you
Lord Kelvin (1827 - 1907) :When you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind; it may be the beginning of knowledge, but you have scarcely in your thoughts advanced to the state of Science, whatever the matter may be.