3D assessment of fracture of sand particles using discrete element method

Shearing or compression of granular materials causes particles to translate and rotate relative to each other, interlock or fracture depending on their mineralogy, morphology, porosity, applied stresses and boundary conditions. Conventional soil plasticity theories consider mainly the stress level and density to predict soil failure and ignore the influence of particle fracture. However, recent research has shown that there is a strong relationship between granular particle fracture and plastic yielding and hardening. In this study, the fracture of individual silica sand particles was modelled by adopting the bonded particle model concept within the framework of the discrete element method (DEM). Individual three-dimensional (3D) particles were generated as an agglomerate of a large number of small spherical sub-particles that were connected by parallel bonds that resist moment and tension at contact points. The tensile strength variation observed when testing natural silica sand was achieved by changing the shape of the particle, the size and distribution of the spherical sub-particles and their bond strength. The onset and propagation of cracks through the particle were investigated using DEM and verified experimentally using 3D synchrotron micro-computed tomography images of sand. The behaviour across the scale from a single particle to a laboratory-size specimen is also presented and discussed.