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REG 363 SITE INVESTIGATIONS

GEOTECHNICALGEOTECHNICAL INSTRUMENTATION

Dr Naser GhaniPhD, P.Eng, MIEM, MASCE, MACEM

anaser@usm.mywww.hbp.usm.my/naserROOM 104 E49

IntroductionIntroduction

We live in a heavily We live in a heavily instrumented society instrumented society and systemsand systems

Geotechnical InstrumentsGeotechnical Instruments

… to provide information on the condition of the ground or the supported structures.. And the their ppconditions when subjected to external influences.

Method and ScopeMethod and Scope

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Role of InstrumentationRole of Instrumentation

In geotechnical works, instrumentation is very In geotechnical works, instrumentation is very important and vital compared to other important and vital compared to other engineering works such as structures.engineering works such as structures.

This is because there is an established properties This is because there is an established properties of structural materials but soil varies widely andof structural materials but soil varies widely andof structural materials but soil varies widely and of structural materials but soil varies widely and there are so many parameters involved.there are so many parameters involved.

Instrumentation provides vital information Instrumentation provides vital information regarding the possible behavior of the soil. It regarding the possible behavior of the soil. It assists the safe and economic design and assists the safe and economic design and construction works. construction works.

What do we normally measure?What do we normally measure?

PorepressurePorepressurepp

EarthpressureEarthpressure

Settlement/deformationSettlement/deformation

Principle application of Principle application of geotechnical instrumentationgeotechnical instrumentation

Site InvestigationSite Investigation

Construction ControlConstruction Control

P f M it iP f M it i Performance MonitoringPerformance Monitoring

Large scale testsLarge scale tests

Site InvestigationSite Investigation

Instrument are used to characterize the Instrument are used to characterize the initial site condition. The parameters of initial site condition. The parameters of interest are ground water tableinterest are ground water tableinterest are ground water table, interest are ground water table, permeability and permeability and strength.strength.

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Construction controlConstruction control

Instruments are used to monitor the effect Instruments are used to monitor the effect of construction and to provide early of construction and to provide early

i f ibl f il Thi f ibl f il Thwarning of possible failures. The warning of possible failures. The instrumentation can also provide instrumentation can also provide information on how fast the construction information on how fast the construction can proceed without the risk of failure.can proceed without the risk of failure.

Performance monitoringPerformance monitoring

Instruments can be used to provide Instruments can be used to provide information of a structure in service information of a structure in service conditioncondition

Large scale testsLarge scale tests

Instrumentation can provide useful Instrumentation can provide useful information on the design assumption andinformation on the design assumption andinformation on the design assumption and information on the design assumption and performances of the structures.performances of the structures.

Measurement of water pressureMeasurement of water pressure

assess ground water level and season assess ground water level and season variationvariation

Evaluate and predict slope stabilityEvaluate and predict slope stability Assess stability and control the rate ofAssess stability and control the rate of Assess stability and control the rate of Assess stability and control the rate of

constructionconstruction Design for lateral and uplift pressureDesign for lateral and uplift pressure Monitor seepageMonitor seepage Monitor the lowering og ground water table Monitor the lowering og ground water table

when dewatering.when dewatering.

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Observation wellObservation well Commonly used Commonly used

for monitoring for monitoring ground water ground water level. The most level. The most widely used type widely used type y ypy ypof piezometer. It of piezometer. It is simple and is simple and reliable but reliable but response time is response time is slow.slow.

Open standpipeOpen standpipe

Hydraulic & Pneumatic Hydraulic & Pneumatic piezometerspiezometers

Hydraulic piezometers Hydraulic piezometers are designed for long are designed for long term monitoring of pore term monitoring of pore water pressures in water pressures in earthfill dam and earthfill dam and embankments. They embankments. They

i fi fHYDRAULIC

comprise of a porous comprise of a porous piezometer tip piezometer tip connected via twin connected via twin tubing to a hydraulic tubing to a hydraulic readout system. The readout system. The readout system readout system incorporates precision incorporates precision pressure gauges.pressure gauges.

PNEUMATIC

Electrical/Electronic piezometersElectrical/Electronic piezometers Vibrating wire Vibrating wire

piezometers are piezometers are designed to measure designed to measure fluid pressures in fluid pressures in boreholes, boreholes, embankments, and embankments, and pressure vesselspressure vesselspressure vessels. pressure vessels. Features include longFeatures include long--term stability in extreme term stability in extreme conditions, high conditions, high resolution and resolution and accuracy, and readings accuracy, and readings not affected by long not affected by long cables. All vibrating cables. All vibrating wire transducers have wire transducers have an inan in--built thermistor to built thermistor to measure temperature.measure temperature.

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DEFORMATIONDEFORMATION

Magnitude of deformation indicates the Magnitude of deformation indicates the overall performance and safety of the overall performance and safety of the constructed facilities.constructed facilities.

Major types of deformation measurement:Major types of deformation measurement: Major types of deformation measurement:Major types of deformation measurement: Vertical and horizontal ground movementVertical and horizontal ground movement

Displacement of structuresDisplacement of structures

Angle changes and distortion of structuresAngle changes and distortion of structures

Measurement of deformation Crack gages

Probe extensometers

Settlement plate

Fixed borehole extensometers Fixed borehole extensometers

Tiltmeters

Inclinometers

In-place inclinometers

Liquid level gages

Measurement of Earth PressureMeasurement of Earth Pressure

Embedment earth pressure Embedment earth pressure llllcells cells

Contact earth pressure cells Contact earth pressure cells

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Earth pressure cellEarth pressure cell RW model instrumentationRW model instrumentation

EPC and LVDTEPC and LVDTLoad and Force/Strain in Structural Load and Force/Strain in Structural

MemberMember

Load cellsLoad cellsLoad cells Load cells

Vibrating wire strain gagesVibrating wire strain gages

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EXCAVATION TUNNELING

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INSTRUMENTATION

Strain gageThis is the most basic form of transducer. It operates on the principle of electrical resistance. It can detect positive or negative strain of the object the gage is bonded to. It can be bonded to metal, concrete, plastic etc. It can be used to construct other type of transducers such as load cell, pressure cell etc.

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INSTRUMENTATIONLVDT can be used to measure displacement or movement of components in the research relative to its position. This is basically an electronic version of dial gage but with more capabilities because the movement can be detected by computers in a very short time interval.

LVDT

INSTRUMENTATION

Load CellLoad cell is used to measure force in tension or compression. Load cell with low and high range capacity are available for various types of loading.

Field instrumentation and transmission

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1) You are the project manager of a land development contractor. This time you are in charge of an earthwork and excavation operation for laying of deep sewer pipe in swampy area. The board of directors ask you to give advise on the requirements for instrumentation and monitoring to ensure safe and economical construction methods for the project.

Take home quiz

List relevant type of sensors and monitoring equipment that can be used and describe their role.

No need to submit. This is totally voluntary and independent study.