Coupled SPH-DEM simulations of liquefaction-induced flow failure

A fully Lagrangian particle-based method for coupled fluid-particle interaction is utilized to evaluate flow liquefaction of saturated granular soils overlain by an impermeable crust. The solid particles are modelled as spherical particles using the discrete element method (DEM). The smoothed particle hydrodynamics (SPH) is employed to model the interstitial fluid using an averaged form of Navier-Stokes equations that accounts for the presence of the solid phase. The coupling between SPH and DEM is achieved through local averaging techniques and well-established semi-empirical formulas for fluid-particle interaction. The responses of loose and dense level granular deposits overlain by an impermeable crust to a seismic excitation are first analyzed. The loose deposit exhibited significant pore pressure development and liquefaction while the dense deposit barely showed any considerable buildup of pore pressure and did not liquefy. The formation of a water film was visible at the interface between the top crust and the underlying liquefied soil. When the same deposits were tilted to form an infinite slope, the loose deposit exhibited flow lgiquefaction at the location immediately underneath the impermeable crust and large shear strains accumulated within a thin layer immediately below the crust. Flow liquefaction was marked by dilative behavior at the surface of the liquefied sand and large lateral spreading that continued post-shaking. Void redistribution was observed along the loose deposit in the form of dilation for a thin layer near sand surface and contraction for the deeper depth. The dense sloping deposit did not liquefy and flow liquefaction was not observed.