June 21, 20061

NEES 4th Annual Meeting

Instrumentation for the NEESR Sand Aging Field Experiment

David A. SaftnerUniversity of Michigan

PhD Student

June 21, 20062

Co-Authors

•Mr Thaweesak

Jirathanathaworn,

UM PhD Student

•Dr Russell Green,

UM Assistant

Professor

SAND AGING

•Ms Jennifer Ngai,

UM Undergraduate

Student

•Dr Jerome Lynch,

UM Assistant

Professor

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Special Thanks

•Dr Richard Woods,

UM Professor

Emeritus

•Mulzer Crushed

Stone, Inc.

•Nicholson

Construction

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•Dr Kyle Rollins,

BYU Professor

•Mr Jan Pantolin,

UM Lab Technician

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Outline

•Sand Aging Overview

•Project Overview

•Parameters and Instrumentation

•Data Acquisition Systems (DAS)

•DAS and Instrumentation Comparison

•Summary

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Sand Aging Overview•Time dependent strength gain without measurable increase in settlement

•First extensive study during Jebba Dam construction on Niger River in Nigeria (1984)

•Increase in soil improvement projects increases importance of sand aging

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Sand Aging Overview

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•Explanations

•Mechanical changes – particle reorientation, particle shearing (Mesri et al, 1990)

•Aging measured after tens of minutes

(figure from Bowman, 2002)

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Sand Aging Overview•Explanations (Continued)

•Chemical changes – creation of cementation through silica gel (Mitchell and Solymar, 1984)

•Denisov & Reltov experiment

•Aging without fabric disruption

•Reduced strength under blast areas

•General theories – pore pressure dissipation, blast gas dissipation, and cold welding

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Project Overview•Site requirements = loose, clean, saturated sand

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Grain Size Distribution Curve for Mulzer Quarry, Griffin, IN

0

20

40

60

80

100

0.0010.010.1110

Diameter (mm)

%Pass

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Project Overview•Liquefaction induction methods

•Explosive compaction

•Vibro-compaction

•Vibro-seis

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Parameters and Instrumentation•Acceleration

•Micro-electro-mechanical system (MEMS) accelerometers•Piezoelectric accelerometers•Geophones (velocity)

•Allow for calculation of energy dissipationin the soil and its effect on aging

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Parameters and Instrumentation•Settlement

•Sondex settlement tubes

•Determine settlement as a function of depth and time

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Sondex readout w/ probe

Inclinometer casing inside Sondex

corrugated pipe

Sensing ring (magnet)

Inclinometer and sensing ring installed at

stable ground

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Parameters and Instrumentation•Pore Water Pressure

•Pore pressure transducers

•Will ensure that liquefaction is induced

•Multiple sensors will monitor spatial generation and dissipation of excess pore pressure

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Parameters and Instrumentation•Sampling Rate

•Acceleration – based on testing method•Settlement – weekly•Pore Pressure – 1 Hz

•Sampling Duration•Acceleration – based on testing method•Settlement – UTC•Pore Pressure – until conditions return to hydrostatic (we expect hours)

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Data Acquisition Systems•Olson Instruments, Inc. Freedom Data PC

•16 channels

•User defined sampling

rate

•20 GB hard drive

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Data Acquisition Systems•Wireless Data Acquisition System (DAS)

•128 kB RAM

•Transmits data up to 300m at 38.4 KB/s

•Sampling rates: 50, 70, 100, 200, 400, & 500 Hz

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• Shaker moving at 10 Hz

• Manifold holds pressure up to 1000 psi

DAS Comparison

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DAS Comparison

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•Geophones output 7 V per in/sec

•Correct frequency measured in both systems

•Impedance of wireless DAS distorts amplitude

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DAS Comparison

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•Pressure transducers output 5 V per ksi

•Cable based DAS does not recognize DC input

without being reconfigured

•Wireless systems reports correct output

Vol

ts

Time (seconds)

Cable-basedWireless

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Instrumentation Comparison

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•Emplacing Instrumentation•Geophones

•MEMS &

Piezoelectric

Accelerometers

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Summary•Sand aging = time-dependent strength gain

•Measure acceleration, settlement, and pore

pressure dissipation caused by three liquefaction

methods

•Different DAS appropriate for different instruments

•Emplacement methods next step in determining

which instruments will be used

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June 21, 200621

Questions?

http://www-personal.umich.edu/~rugreen/NEES/