NEES 4th Annual Meeting

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NEES 4th Annual Meeting

Instrumentation for the NEESR Sand Aging Field
Experiment David A. Saftner University of
Michigan PhD Student
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SAND AGING
Co-Authors

• Mr Thaweesak Jirathanathaworn, UM PhD Student
• Dr Russell Green, UM Assistant Professor

• 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

• 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

• 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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SAND AGING
Project Overview

• Site requirements loose, clean, saturated sand

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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 dissipation
• in 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

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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DAS Comparison

• Shaker moving at 10 Hz
• Manifold holds pressure up to 1000 psi

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DAS Comparison

• 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

• Pressure transducers output 5 V per ksi
• Cable based DAS does not recognize DC input
  without being reconfigured
• Wireless systems reports correct output

Cable-based Wireless
Volts
Time (seconds)
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Instrumentation Comparison

• 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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Questions? http//www-personal.umich.edu/rugree
n/NEES/