Pore Pressure Measurement in Blast-Induced Liquefaction Experiments

Abstract

Blast-induced liquefaction experiments have been conducted at a number of test sites to evaluate lateral foundation resistance and soil improvement techniques. Tests can be constructed at full scale without waiting for an earthquake. In this extreme environment, pore pressure transducers must survive transient blast pressures of 41.4 MPa (6,000 psi) yet have enough resolution to measure residual pore pressures of ±0.69 kPa (0.1 psi). Three transducer types were evaluated under these demanding conditions, and the piezoresistive transducer was found to be the most robust. These sensors were repeatedly subjected to extreme blast pressures and vibration, but they still provided accurate time histories of residual pore pressure. Although these piezometers are more expensive than other types, installation techniques allowed them to be recovered and reused in subsequent tests and thus reduced overall costs. These pore pressure sensors make it possible to define the extent of the liquefied zone during blast liquefaction experiments and to understand the soil behavior during cyclic loading of deep foundations.