Advancements and Innovations in Instrumentation Systems for

Real-Time Monitoring of Geo-Hazards

W. Allen Marr, PhD, P.E.

Thomas Allen Tye, P.E.

Geocomp Corporation

Boxborough, MA

www.geocomp.com

Subtopics

Why monitor performance?Why monitor performance?WhatWhat’’s new in measurement technologies?s new in measurement technologies?Why automate?Why automate?Benefits to Contractors, Engineers and Benefits to Contractors, Engineers and OwnersOwnersFactors favoring monitoringFactors favoring monitoringWrap UpWrap UpConclusions Conclusions ––

There are new and significant roles for realThere are new and significant roles for real--time performance monitoring of time performance monitoring of construction.construction.

Why monitor performance?1.1. Indicate impending failure.Indicate impending failure.2.2. Provide a warning.Provide a warning.3.3. Reveal unknowns.Reveal unknowns.4.4. Evaluate critical design assumptions.Evaluate critical design assumptions.5.5. Assess contractorAssess contractor’’s means and methods.s means and methods.6.6. Minimize damage to adjacent structures.Minimize damage to adjacent structures.7.7. Control Construction.Control Construction.8.8. Control Operations.Control Operations.9.9. Devise remedial measures to fix problems.Devise remedial measures to fix problems.10.10. Improve performance.Improve performance.11.11. Advance stateAdvance state--ofof--knowledge.knowledge.12.12. Document performance for assessing damages.Document performance for assessing damages.13.13. Inform stakeholders.Inform stakeholders.14.14. Satisfy regulators.Satisfy regulators.15.15. Reduce litigation.Reduce litigation.16.16. Show that everything is OK.Show that everything is OK.

Why monitor performance?TO SAVE MONEY TO SAVE MONEY

Save LivesSave LivesMinimize DamagesMinimize DamagesAvoid DelaysAvoid DelaysSave face Save face –– protect reputationprotect reputation

Monitoring indicates unexpected Monitoring indicates unexpected performance and surprises before the performance and surprises before the consequences become large and consequences become large and costly.costly.

Monitoring provides a strong tool to Monitoring provides a strong tool to help manage operational risks.help manage operational risks.

Consequences can be seriousSingapore

DullesOne killed, two trapped

Why monitor performance?Because a significant number of projects Because a significant number of projects develop surprising behavior that leads to develop surprising behavior that leads to increased costs and delays.increased costs and delays.

Many projects have major deficiencies in the site Many projects have major deficiencies in the site investigation, testing, analysis or implementation investigation, testing, analysis or implementation of recommendations.of recommendations.Even with the best of site investigations, testing, Even with the best of site investigations, testing, analysis and construction monitoring, we are still analysis and construction monitoring, we are still frequently surprised by actual performance.frequently surprised by actual performance.Diminished involvement of design engineer in the Diminished involvement of design engineer in the construction.construction.Large tendency for the Contractor to ignore or Large tendency for the Contractor to ignore or avoid engineeravoid engineer’’s advice and perform the work in s advice and perform the work in their own ways, many times with inexperienced their own ways, many times with inexperienced staff.staff.

•Consequences can be expensive.small slope failure because contractor dug too deep

•Contractor filed claim for $12,000,000 damages from delays •Contractor awarded $6,000,000 by Review Board with no knowledge of soil mechanics.

Why monitor performance?

TO LOWER RISKTO LOWER RISKRISK = Probability of Failure * ConsequencesRISK = Probability of Failure * ConsequencesGood monitoring can reduce probability of Good monitoring can reduce probability of failure.failure.Good monitoring can reduce consequences by Good monitoring can reduce consequences by giving a reliable warning. Consequences can be giving a reliable warning. Consequences can be very significant.very significant.

•• Loss of lifeLoss of life•• Damage to other property Damage to other property •• Loss of facilityLoss of facility•• Costs to mitigate and repairCosts to mitigate and repair•• DelaysDelays•• Damage to reputationDamage to reputation

Dam cracking

Earth Dam with good, conservative practice, Whitman, 1984

1 in 20,000

Earth Dam with good, conservative practice, Whitman, 1984 – poor monitoring

40-fold decrease achieved by monitoring.Performance monitoring can be a very effective approach to reducing risk.

1 in 500

Dam cracking

Why monitor performance?Monitoring is important component of Risk Management.To manage anything you must measurekey performance indicators.

What are the risks?

What performance parameters can we measure?

DeformationDeformationStrainStrainTiltTiltPore water Pore water pressurepressureEarth Earth pressurepressureVelocityVelocityAccelerationAccelerationFlow RateFlow RateTurbidityTurbidity

TimeTimeTemperatureTemperatureHumidityHumidityWind speed Wind speed and directionand directionPrecipitationPrecipitationSoil MoistureSoil MoistureLight IntensityLight IntensitySound Sound IntensityIntensity

pHConductivityBOD and CODGas flow rateCorrosion rateSpecific targets

VOCsMetalsBacteriumMolds

PHYSICAL CHEMICAL &BIOLOGICAL

ENVIRONMENTAL

Measuring PerformanceGreat equipment available to measure Great equipment available to measure field performance reliably and quickly.field performance reliably and quickly.

Crack gage

Tilt beam-Electro-level

Deformation - Distance change by laser

Measurement range Measurement range -- 0.2 to 0.2 to 200 m200 mTypical accuracy Typical accuracy ++ 1.5mm1.5mmMeasurement time 0.6 to 4 Measurement time 0.6 to 4 secsecHundreds of targets per ATSHundreds of targets per ATSRemotely controllableRemotely controllableUse for automated monitoring Use for automated monitoring and alarmingand alarming

Deformation - Distance change by GPS

Measurement range Measurement range --unlimitedunlimitedTypical accuracy Typical accuracy ++ 3 mm3 mmMeasurement time 0.1 to 10 Measurement time 0.1 to 10 secsecNo moving parts. No moving parts. Use for automated monitoring Use for automated monitoring and alarmingand alarming

In place inclinometers

Reliably measure deflections to 1 mm.

TiltTilt sensor Tilt beam-Electro-level

Resolution to better than 0.1 mm per 10 m

Displacement - Crack Monitoring

Displacement transducerResistive crack gages

Resolution to better than 1 μm

Head with electrical displacementtransducers for multipointtelltale-type extensometers

Resolution to better than 1 μm

Deformation - Borehole telltale extensometers

Strain - Resistive strain gauges

0.015”

4.0”

Glued onto cement

Welded onto steel0.5”

Resolution to better than 1 μstrain

Strain - Vibrating wire extensometerEmbed in Embed in concrete pour.concrete pour.% L/L gives % L/L gives average strain in average strain in concreteconcreteLess sensitive to Less sensitive to electrical noise electrical noise and moisture.and moisture.

Units for embedment in concrete

10 inches

Resolution to 1 μstrain

Piezometer with Electrical Transducer

Pressure transducer Pressure transducer sealed in an isolated sealed in an isolated location.location.Gives immediate Gives immediate response to change response to change in pore pressure.in pore pressure.Seal above Seal above transducer is very transducer is very important.important.Grout several in Grout several in same hole.same hole.

Vibrating wire piezometers

Load Cells to Measure Force

Hold down anchorsHold down anchorsTiebacksTiebacks

Velocity and AccelerationSEISMOGRAPHSEISMOGRAPH

Continuously records peak Continuously records peak velocities (or velocities (or accelerations) in a accelerations) in a specified interval.specified interval.

Records complete time Records complete time history of vibrations that history of vibrations that exceed a trigger level.exceed a trigger level.

Can automatically issue Can automatically issue alarm messages. alarm messages.

Powered by battery or Powered by battery or solar panelsolar panel

Center of Site - Vibratory Driving of Piles

0.01

0.1

1

10

1 10 100Frequency (Hz)

Peak

Par

ticle

Vel

ocity

(in/

sec)

OSM Criteria * Longitudinal Transverse Troublesome Vertical

Troublesome to People

Damage Threshold

Perceptible to People

Dynamic strain gages

Temperature sensors

3 mm can

0.25”Weldable

Thermisters in a string

Example of temperature sensitivity

temperature

displacement

Web-Based, Real-Time, Remote Monitoring

Web EnabledSettings

Internet

I-20 at Vicksburg, MS

Old ScarpOld Scarp

GrabenGraben

II--2020USUS--8080

History of eastern bank

1876 opening of Centennial cutoff causing Mississippi 1876 opening of Centennial cutoff causing Mississippi channel to move towards east bankchannel to move towards east bank1929 ground crack formed 900 ft upstream and 600 ft 1929 ground crack formed 900 ft upstream and 600 ft downstream of USdownstream of US--80 bridge construction80 bridge construction1930 US1930 US--80 bridge completed80 bridge completed19331933--1942 drop in river stage due to construction of 1942 drop in river stage due to construction of cutoffs upstreamcutoffs upstream19401940--1943 east bank slope flattened1943 east bank slope flattened1973 I1973 I--20 bridge completed20 bridge completed20002000--2004 measurements show movements at elevation 2004 measurements show movements at elevation ––34 to 34 to ––65 ft (Forest Hill formation) during low river stages.65 ft (Forest Hill formation) during low river stages.20042004-- tests show Forest Hill soils have residual strength of tests show Forest Hill soils have residual strength of 6 to 12 degrees.6 to 12 degrees.

History of movements – concern for integrity of I-20 bridge

Pier EPier E--11Pier EPier E--22

Recent Horizontal Movements

Movements Occur when River Drops to Low StageMovements Occur when River Drops to Low Stage

Complex interaction of river, rainfall, geometry and soil properties

New instrumentationEnhanced realEnhanced real--time monitoring system in advance of time monitoring system in advance of construction of remedial measures to warn of new construction of remedial measures to warn of new movements and evaluate effectiveness of remedial measures.movements and evaluate effectiveness of remedial measures.

Five new inclinometers with 15 biaxial inFive new inclinometers with 15 biaxial in--place MEMS inclinometers place MEMS inclinometers in each.in each.Wireless data loggers for these and one existing inclinometer wiWireless data loggers for these and one existing inclinometer with th Sinco IPI in place.Sinco IPI in place.3 vibrating wire piezometers outside each new inclinometer grout3 vibrating wire piezometers outside each new inclinometer grouted ed in at various elevations.in at various elevations.iSiteCentral WebiSiteCentral Web--based monitoring system logging data several times based monitoring system logging data several times per day with alarms and immediate availability of the data plottper day with alarms and immediate availability of the data plotted ed with time. with time.

Field Test of dewatering wells to lower pore water pressures Field Test of dewatering wells to lower pore water pressures in slope and increase factor of safety in vicinity of bridge.in slope and increase factor of safety in vicinity of bridge.

Rebuilding the World Trade Center – New York CityMonitoring of Active Subway through the Site

Rebuilding the World Trade Center – New York CityMonitoring for Existing Slurry Wall

Rebuilding the World Trade Center – New York City

WTC – Instant screen view

Advanced Numerical Analysis

PLAXIS Analysis to determine factor of PLAXIS Analysis to determine factor of safety for global stability and for estimating safety for global stability and for estimating settlement of the mat foundationsettlement of the mat foundation

Automated Total Stations (2)Automated Total Stations (2)Over 110 targets within excavation and on Over 110 targets within excavation and on surrounding buildingssurrounding buildings22 nested piezometers22 nested piezometersFive automated inclinometersFive automated inclinometersTwo flow metersTwo flow metersFour automated crack gagesFour automated crack gagesAccessible in real time by iSiteCentral.comAccessible in real time by iSiteCentral.com

Ellis Square Project Instruments

Set up remotely at the Site

Monitoring the Buildings…

..and Inside the Excavation

In-Place Inclinometers

Why monitor in real time?Failure can occur rapidly with little visible Failure can occur rapidly with little visible warning, even for where ground has been stable warning, even for where ground has been stable for years.for years.

Global instability Global instability –– shear slide shear slide -- weeks to few hoursweeks to few hours

Internal instability Internal instability –– internal erosion internal erosion –– pipingpiping-- years to few hoursyears to few hours

Other Other –– soil/structural failuresoil/structural failureyears to minutesyears to minutes

Failure may be avoided using preventative Failure may be avoided using preventative actions, if we have adequate warning.actions, if we have adequate warning.Consequences can be reduced significantly if we Consequences can be reduced significantly if we have a reliable warning.have a reliable warning.

Factors affecting monitoring frequency

Rate at which performance mechanism can Rate at which performance mechanism can change change

(deformations for excavation may be so small they can(deformations for excavation may be so small they can’’t be t be reliably detected with manual monitoring; then within reliably detected with manual monitoring; then within hours rate accelerates to failure)hours rate accelerates to failure)

Consequences of poor performanceConsequences of poor performanceAre lives or major facilities at risk?Are lives or major facilities at risk?

Environmental effects on facilities and Environmental effects on facilities and instrumentationinstrumentation

Temperature, humidity, precipitation, sun, windTemperature, humidity, precipitation, sun, wind

For monitoring to be effective, data retrieval, evaluation and action must occur fast enough to capture early warning signs and avoid unacceptable performance.

Trends in monitoring for damage control

Cost and frequency of claims are increasingCost and frequency of claims are increasingRegulatory requirements for monitoring are Regulatory requirements for monitoring are increasingincreasingIncreasing need to monitor effects more Increasing need to monitor effects more preciselypreciselyMore people are recognizing the benefits of More people are recognizing the benefits of good monitoringgood monitoringEquipment is more reliable and less costlyEquipment is more reliable and less costlyMonitoring costs are decreasingMonitoring costs are decreasingMethods to deliver timely data are improving.Methods to deliver timely data are improving.

New Benefits from MonitoringReduce riskReduce risk

Predict and avoid failure by revealing unknowns/surprises.Predict and avoid failure by revealing unknowns/surprises.Minimize damage to adjacent structures.Minimize damage to adjacent structures.Document performance for assessing damages. Document performance for assessing damages. Reduce litigation. Reduce litigation. Control construction to avoid delays. Control construction to avoid delays. Use data to preserve job safety and control means and methodsUse data to preserve job safety and control means and methods

Demonstrate Quality, especially for designDemonstrate Quality, especially for design--build.build.Devise remedial methods to fix problems.Devise remedial methods to fix problems.Document performance for advancing claims.Document performance for advancing claims.Inform parties by answering questions and calming fears.Inform parties by answering questions and calming fears.Improve construction processes. Improve construction processes. Help deal with politically sensitive projects.Help deal with politically sensitive projects.Reduce cost of future construction.Reduce cost of future construction.

Factors encouraging more monitoringComplex or unknown site conditionsComplex or unknown site conditionsSituations where behavior can change suddenlySituations where behavior can change suddenlyLack of prior experienceLack of prior experienceNew construction materials/processesNew construction materials/processesSituations with strong pressure to lower costsSituations with strong pressure to lower costsTight restrictions and regulationsTight restrictions and regulationsHigh consequences from failure, damages or High consequences from failure, damages or delays.delays.Concerns about litigation for damages.Concerns about litigation for damages.Politically sensitive projectsPolitically sensitive projects

ConclusionsEffective monitoring programs can save moneyEffective monitoring programs can save money--

Indicate need for protective measures before damage occursIndicate need for protective measures before damage occursReduce consequences of failure by providing a warning.Reduce consequences of failure by providing a warning.Reduce Risk to 1/10 to 1/100 that of an unmonitored facilityReduce Risk to 1/10 to 1/100 that of an unmonitored facility

Effective monitoring programs need to be realEffective monitoring programs need to be real--time.time.Unit Costs of realUnit Costs of real--time monitoring are decreasingtime monitoring are decreasing

Better and cheaper sensors and data acquisition hardwareBetter and cheaper sensors and data acquisition hardwareLower cost of data collection, reduction and evaluation from Lower cost of data collection, reduction and evaluation from new electronics, computers and telecommunications new electronics, computers and telecommunications –– iSite and iSite and iSiteCentraliSiteCentral

Contractors and civil engineers need to modernize their Contractors and civil engineers need to modernize their approach to instrumentation and monitoring by using approach to instrumentation and monitoring by using current technology to better identify, monitor and current technology to better identify, monitor and manage risk to life and property.manage risk to life and property.

September 24September 24--27, 200727, 2007Boston, MassachusettsBoston, Massachusetts

th FMGM – Boston, MASeptember 24-27, 2007.