Numerical Modeling of Shear Behavior in Rough Joints of Unsaturated Sandstone

Using a tessellation method in Neper, the simplified 3DEC-GBM (three-dimensional discrete element grain–based model) is proposed for generating joint models with different roughnesses. The model is extended by implementing the generalized effective stress law to mimic the shear behavior of unsaturated sandstone. The grain-scale mechanical parameters of the model were calibrated to correspond to the mechanical behavior of sandstone samples measured in the laboratories. The simulations accurately explain complex macroscopic shear behavior in terms of the mesoscale interaction of grains. The modeling results show that water has a deteriorating effect that weakens the strength of the joint, and the degree of reduction in joint strength rises with increasing saturation. Increasing normal stress and roughness can all improve the shear strength of the joint. We conclude that the proposed model is a convenient approach to analyze the shear response of unsaturated sandstone at varying roughness and normal stress.