Shear behavior and fracturing mechanism of intact sandstone affected by spatio-temporally varying water

Abstract

Water in rock engineering varies both temporally and spatially. In this study, direct shear tests were performed on dry and saturated intact sandstone samples to study the effects of water on shear behavior. Subsequently, the rock failure process analysis (RFPA) 2D humidity method was developed and applied to perform simulations of the direct shear fracturing process of intact sandstone samples with spatio-temporally varying water. The numerical results showed a significant decrease in the peak/residual shear strength and shear stiffness with the increase in the humidity diffusion time. Under direct shear, the macroscale shear fault observed was mainly due to the progressive failure of the numerous tension-induced microcracks and water facilitates the development of tensile cracks. The uniformly distributed humidity weakened the heterogeneities of the rock material and the stress field in the rock, making the cracks to mainly develop near the predetermined shear plane. The nonuniformly distributed humidity strengthened the heterogeneities of the rock material and the stress field in the rock; the longer the humidity diffusion time, the stronger the strengthening effect. Consequently, cracks developed not only near the predetermined shear plane, but also in the humidity-affected region, forming several en-echelon fractures in the unsaturated samples.