Microscale Modeling of the Seismic Response of Shallow Foundations

This paper presents a microscale approach to analyze the seismic response of a spread footing system founded on a liquefiable granular soil deposit. The approach utilizes a three-dimensional transient fully-coupled hydromechanical model while taking into account the effects of soil-foundation interaction. The porous soil medium is modeled as a mixture of two interpenetrating phases, namely the fluid phase (water) and the particulate solid phase. The fluid is idealized as a continuum by using averaged Navier-Stokes equations that account for the presence of the solid particles. The Discrete Element Method (DEM) is employed to model the assemblage of these particles. The interphase momentum transfer is modeled using an established relationship that accounts for the dynamic change in porosity. The spread footing is idealized as a rigid block and its motion is described by the resultant forces and moments acting upon it. A computational simulation is conducted to investigate the response of spread-footings on a saturated granular deposit when subjected to a dynamic excitation. Results of the conducted simulation showed that the foundation sustained excessive settlement as the ground shaking progressed. The conducted simulation appears to capture essential dynamic response patterns typically observed in such systems.