Research Initiation: Insitu Pore Water Pressure Predictions During Earthquakes
When loose sands saturated with water are subjected to the cyclic loads resulting from severe earthquake shaking, excess pore water pressures are generated if the water cannot easily drain away (undrained behavior). This excess pore pressure reduces the soil strength, and if sufficient pressure is generated, will lead to a failure of the soil referred to as liquefaction. Current methods for predicting the generation of pore water pressure during cyclic loading often overpredict the pressures generated, that is, they result in conservative predictions. This research project is investigating the accuracy of soil models currently used for the prediction of earthquake-generated pore water pressures, with special attention being given to the effect of the dissipation of this pressure during and after the earthquake. The predictions are being compared with laboratory test data as well as data obtained from field tests using an instrumented site at Owi Island, Tokyo Bay, Japan. This data includes ground motion time histories as well as dynamic pore water pressure measurements at two depths in the loose sandy subsoils.