Physics engine based simulation of shear behavior of granular soils using hard and soft contact models

Abstract

Physics engines have been widely used to simulate physical and mechanical processes in modern video games to create an immersive and realistic gaming experience. This study explores the feasibility of using an open-source physics engine, Chrono, as a discrete element method (DEM) platform to simulate shear behavior of granular soils. This study develops a series of pre-processing, servo-controlling, and post-processing functions to improve the Chrono platform, so that Chrono can generate soil specimens with designed packing densities, perform laboratory test simulations such as direct shear tests, and output stress-strain, fabric, and force chains. Traditional DEM codes use soft contact models (e.g., Hertzian contact model) to determine inter-particle contact forces, while most physics engines use a hard contact model (e.g., non-smooth contact dynamics) to determine inter-particle contact forces. The hard contact model enables physics engines to use large time steps in iterations without affecting the numerical stability and simulation accuracy, which remarkably accelerate simulation speeds compared with traditional DEM codes. Based on systematical comparisons between simulation results of two contact models and experimental results, this study demonstrates that the hard contact model can yield the shear behavior of granular soils observed in soft contact model simulations and laboratory tests.