Coupled smoothed particle hydrodynamics-discrete element method simulations of soil liquefaction and its mitigation using gravel drains

Abstract

In this paper, a fully Lagrangian particle-based method for coupled fluid-particle interaction is utilized to evaluate liquefaction of saturated granular soils subjected to dynamic base excitations. The discrete element method (DEM) is employed to model the solid particles and the fluid motion is simulated using the smoothed particle hydrodynamics (SPH). A coupled SPH-DEM scheme is achieved through local averaging techniques and well-established semi-empirical formulas for fluid-particle interaction. A key feature of the employed technique is that it does not presume undrained conditions for the granular deposit and allows for spatial fluid movements within the deposit. The responses of loose and dense granular deposits to seismic excitation are first analyzed. As expected, 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. Liquefaction of the loose deposit resulted in significant surface settlement while that experienced by the dense deposit was within tolerable limits. A liquefaction mitigation technique through the installation of gravel drains was then introduced to the loose deposit and its effect on mitigating pore pressure buildup was examined. Results of conducted simulations show that the installation of gravel drains effectively reduced pore-pressure buildup and, for the most part, the soil maintained its strength. However, the drains did not reduce the overall surface settlement of the deposit to acceptable levels.