Experimental and numerical study on the mechanical behaviors and crack propagation of sandstone containing two parallel fissures

For the rocky slope with potential sliding hazard, there are a larger number of flaws such as fractures and joints, which greatly affect the stability and safety of the slope. Thus, it is important and relevant to the behavior of fractured rock from a macroscopic and mesoscopic perspective by experiments and numerical simulation. In this paper, the mechanical properties and crack evolution behavior of grey sandstone containing two parallel fissures under the uniaxial compression tests were evaluated by experimental and bond-based Peridynamics (BB-PD) simulation. The results show that with the increase of fissure dip angle, the peak strength, elastic modulus and Poisson's ratio of pre-cracked sandstone samples under uniaxial compression condition gradually increase. At the same time, the total energy, dissipated energy and elastic peak energy of fractured sandstone also increase with the increase of fissure dip angle. In order to validate the experimental findings, a set of calibration parameters were used to model the intact samples using BB-PD. The numerical simulation reproduced the stress-strain curves, mechanical parameters and failure modes of double-fractured sandstone. Based on the results of indoor experiments and numerical simulations, it is concluded that the failure mode of double-fractured sandstone has three types under uniaxial compression: tensile failure, shear failure and conjugate shear failure. As the fissure dip angle increases, the main control factor for failure of sample gradually changes from rock bridge failure to secondary crack coalescence, and the stress distribution of fractured sandstone gradually changes from high stress concentration in the rock bridge zone to uniform stress distribution as a whole.