SPH-DEM modeling of the seismic response of shallow foundations resting on liquefiable sand

Abstract

In this study, the seismic response of shallow foundations resting on a liquefiable soil layer is modeled using a coupled smoothed particle hydrodynamics (SPH)-discrete element method (DEM) scheme. In this framework, the soil deposit is represented by an assembly of DEM particles and the fluid domain is lumped into a set of SPH particles carrying local fluid properties. The averaged forms of Navier-Stokes equations dictate the motion of the fluid-particle mixture and the interphase forces are estimated using well-known semi-empirical equations. A saturated soil-foundation system with an average contact pressure of 50 kPa was created using the coupled scheme. The foundation block was composed of a collection of DEM particles glued together by high-stiffness bonds. No-penetration boundary condition was applied to all sides of the foundation block to allow for fluid-foundation interaction. The model was subjected to a strong base acceleration and the response was analyzed and compared to the free-field. The ground settlement in the soil-foundation system mostly originated from co-seismic deviatoric deformations while volumetric strains were the main contributing factor at the free-field. In addition, the impact of soil permeability on the seismic response of the soil-foundation system was examined by changing the pore fluid viscosity. According to the results, as the soil permeability decreased, smaller excess pore pressures developed beneath the footing thanks to the slower migration of pore fluid from the sides and bottom, and a larger magnitude of soil strength and stiffness was maintained in the expansive zone. As a result, the system with the lowest permeability experienced the smallest foundation settlement while the foundation acceleration amplitude was the highest in this case. The results also showed that the percentage of post-shaking settlement appreciably increased in the lower-permeability deposits. The results of this study were compared with the published centrifuge studies that showed good qualitative consistency. • A SPH-DEM scheme is utilized to model the seismic response of shallow foundations on liquefiable soils. • Averaged form of Navier-Stokes equations are used to describe the pore fluid motion in the mixture. • The foundation block was composed of a collection of DEM particles glued together by high-stiffness bonds. • No-penetration boundary condition was applied to all foundation sides to allow for fluid-foundation interaction. • The results of this study qualitatively agree with published centrifuge studies.