Incremental effective stress liquefaction modelling of sands

• Main Author: McIntyre, Jay Duncan
• Language: English
• Published: 2009
• Online Access: http://hdl.handle.net/2429/4426

A one dimensional incremental effective stress liquefaction model is presented. Two versions of the model have been developed - a static model to simulate the behaviour of a sand element to laboratory cyclic simple shear tests, and a dynamic model to compute the response of sand under harmonic or earthquake loading. For undrained cyclic loading, neither model incorporates strain softening response typical for loose sands, but have been calibrated to predict the response type known as cyclic mobility. The static version of the model is calibrated to match characteristic laboratory cyclic simple shear test results. Comparisons between laboratory results and modelled data are presented. The dynamic version of the model incorporates the key components of the static model, and can be used to predict the response of a simplified soil profile under dynamic loading. In particular, earthquake acceleration time history records may be used as input. The dynamic model was applied to simulate the field case history recorded at the Wildlife Site in California during the 1987 Superstition Hills earthquake. The recorded downhole acceleration time history was used as input for the dynamic model and the predicted response, in terms of surface acceleration, relative displacement, and porewater pressure, compared with the measured values. The predicted acceleration and displacement time histories are in good agreement with the measured values in terms of both the amplitude and characteristic frequency of response. The predicted porewater pressures are not in good agreement with the recorded values. The predicted porewater pressure rise is much faster than the measured data. The slower response may be due to limitations in the compliance of the measuring system and to the possibility that liquefaction did not occur simultaneously at all points in the liquefied layer.