Numerical simulation of earthquake-induced pore pressure response of saturated sand layer in a partial drainage environment

抄録

The earthquake-induced pore pressure response of a 5-m clean Ottawa F-65 sand layer of 45% relative density, under an effective overburden of 1 atm and subjected to earthquake base excitation, is numerically simulated. The layer sits on an impervious boundary and is free to drain at the top to simulate a possible partial drainage condition in the field. Numerical software FLAC and constitutive model PM4Sand are used for the simulation. The model is calibrated using the results of an available high-quality centrifuge experiment conducted in the Geotechnical Centrifuge Facility at Rensselaer Polytechnic Institute. Extensive instrumentation was utilized in the experiment to measure the dynamic soil response, including time histories of acceleration, pore water pressure and displacement, as well as bender elements measurements of shear wave velocity. Furthermore, System Identification is used to back-figure time histories of shear stress and shear strain. The instrumentation at different elevations in the experiment provided a comprehensive coverage of the soil response, which supported a system-level model calibration. A brief parametric study of the model’s input parameters preceded the model calibration in order to investigate how they affect the system-level behavior and to establish a proper calibration procedure. The predictions of the calibrated model are in excellent agreement with the records from the centrifuge, providing a strong basis for using the calibrated model to extend the results of the centrifuge experiment to other earthquake input motions, sand layer thicknesses and drainage boundary conditions. The calibrated numerical simulation was repeated after changing the layer thickness from 5 m to 10 m. The results of the new simulation are discussed to illustrate the possibilities of the new calibrated numerical tool.