Numerical simulation of rock fracture using three-dimensional extended discrete element method

We perform three-dimensional numerical simulation of rock fracturing under uniaxial compression by extending the discrete element method (DEM). Rock sample is modeled as an assemblage of about four thousand spheres having the same radius. Each element satisfies equations of motion for both translation and rotation. In extension of the DEM, we assume cohesion between elements and constrained rotation of the elements; these assumptions are required to treat the continuum by the DEM. We study two cases of uniaxial compression tests: A homogeneous sample having an equal cohesion force between elements and heterogeneous sample having weak parts of cohesion in one percent of the total number of the bonds of elements. We present the detail of fracturing process of model rock samples and obtain stress-strain curve for each case. The homogeneous sample shows a cone-shaped fault system, whereas the heterogeneous sample shows complex fault system consisting of major and sub faults. We find that the inner stress and rotation of elements show the negative correlation during fracturing process. The results are in good agreement with both experimental and theoretical results.