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NEES 4 th Annual Meeting

NEES 4 th Annual Meeting. Instrumentation for the NEESR Sand Aging Field Experiment David A. Saftner University of Michigan PhD Student. SAND AGING. Co-Authors. Mr Thaweesak Jirathanathaworn, UM PhD Student Dr Russell Green, UM Assistant Professor.

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NEES 4 th Annual Meeting

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  1. NEES 4th Annual Meeting Instrumentation for the NEESR Sand Aging Field Experiment David A. Saftner University of Michigan PhD Student

  2. 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

  3. SAND AGING 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

  4. SAND AGING Outline • Sand Aging Overview • Project Overview • Parameters and Instrumentation • Data Acquisition Systems (DAS) • DAS and Instrumentation Comparison • Summary

  5. SAND AGING 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

  6. SAND AGING Sand Aging Overview • Explanations • Mechanical changes – particle reorientation, particle shearing (Mesri et al, 1990) • Aging measured after tens of minutes • (figure from Bowman, 2002)

  7. SAND AGING 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

  8. SAND AGING Project Overview • Site requirements = loose, clean, saturated sand

  9. SAND AGING Project Overview • Liquefaction induction methods • Explosive compaction • Vibro-compaction • Vibro-seis

  10. SAND AGING 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

  11. SAND AGING 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

  12. SAND AGING 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

  13. SAND AGING 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)

  14. SAND AGING Data Acquisition Systems • Olson Instruments, Inc. Freedom Data PC • 16 channels • User defined sampling • rate • 20 GB hard drive

  15. SAND AGING 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

  16. SAND AGING DAS Comparison • Shaker moving at 10 Hz • Manifold holds pressure up to 1000 psi

  17. SAND AGING DAS Comparison • Geophones output 7 V per in/sec • Correct frequency measured in both systems • Impedance of wireless DAS distorts amplitude

  18. SAND AGING 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)

  19. SAND AGING Instrumentation Comparison • Emplacing Instrumentation • Geophones • MEMS & • Piezoelectric • Accelerometers

  20. SAND AGING 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

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

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