Verification of the performance of the Multi-Piezometer Array System for the measurement of pore pressures in shallow marine sediments

Abstract

The Multi-Piezometer Array System (MPAS) was constructed and delivered for use to Texas A&M University in the fall of 1996. The MPAS is a highly sophisticated measurement system designed to measure changes in in situ pore pressures in cohesive and non-cohesive sediments. The measurement of pore pressure is made with differential pressure transducers housed in mobile probes. Each probe houses four differential pressure transducers for measuring changes in pore pressure and two total pressure transducers for monitoring the free surface and the reference pressure for the differential pressures. Upon receiving the MPAS a thorough evaluation of the system and it components revealed a number of deficiencies which required attention before the system could be tested and deployed. After completing modifications on the system a number of field and laboratory tests were performed to evaluate the systems ability to produce an accurate record of changes in pressures in pore fluid. After a careful review of the data collected in the field and in the laboratory with the MPAS it was concluded that the measurement of pore pressure by the system was unreliable. The experiments conducted for the thesis showed that the measurement of pressure changes in shallow marine sediments is possible. The experiments conducted also showed that the method and devices used to make this measurement could influence and possibly render the measurement useless.