Simulation of saturated sand site liquefaction based on the CFD-DEM method

Soil liquefaction is a prevalent seismic hazard. However, current laboratory and model experiments studying the dynamic characteristics of sand liquefaction struggle to accurately represent the actual soil liquefaction process. The computational fluid dynamics (CFD) coupled with discrete element method (DEM) simulation method can accurately simulate various soil-water coupling problems. The CFD-DEM flow-solid coupling module facilitated the exchange of mechanical information between the commercial discrete element software PFC3D and the open-source computational fluid dynamics software OpenFOAM. The feasibility of this approach was confirmed through particle underwater free sedimentation experiments. Calibration of numerical sand specimens with dynamic characteristics of real saturated sand was conducted using PFC3D software through simulated laboratory cyclic triaxial tests. Based on the existing parameter information and the coupled simulation method, a site liquefaction model of saturated sand was established. The simulation results indicate that the discrete element method (DEM) can replicate laboratory sand liquefaction experiments, and the calibrated parameters can be applied to site liquefaction simulations. The consistency between the sedimentation velocity of a single particle and theoretical solutions validates the accuracy of the CFD-DEM coupling method. Under a peak acceleration of 0.25g, liquefaction occurs at various depths, and the ratio of excess pore pressure does not exceed 1 during liquefaction. The cumulative excess pore pressure increases from shallow layers to deep layers. After liquefaction, the soil strength gradually recovers from bottom to top, and the soil structure in the re-consolidated site shows a trend of homogenization.