Discrete element simulation of crushable soil

Computer simulations of crushable agglomerates were performed using the PFC3D computer code, which adopts the distinct element method (DEM). Agglomerates were made by bonding elementary spheres in 'crystallographic' arrays, and by giving each sphere an existence probability of 0.8. Weibull statistics of the crushing strength of the resulting agglomerates, when tested singly between parallel platens, matches that of real silica sand grains. Triaxial tests on a cubical sample made of 389 agglomerates were then simulated. Curves of isotropic compression are shown, and the effect of loading rate on the position of the compression curves is discussed in relation to the practical question of performing DEM simulations as fast as possible without creating inertia errors. Other stress paths, including conventional 'drained' triaxial compression, constant mean effective stress, and constant-volume paths, were also simulated from different initial stresses along the virgin e-log p' curve. The numerical results are compared quantitatively with the testing data of the silica sand. They are also discussed in relation to characterising crushable soils during normal compression, yield, and critical states. Simulation of crushable soils using DEM provides valuable insights concerning the micromechanical origins of soil plasticity.