Study on Shear Failure Behavior of Embedded Crack Subjected to Different Normal Stresses

The engineering rock mass contains numerous cracks and joints. The propagation of these discontinuities has a great impact on the stability of rock mass. To investigate the failure behavior of jointed rock mass subjected to shear stress, the present paper simulated the fracture propagation under direct shear stress using the augmented virtual internal bond (AVIB) in conjunction with 3D element partition method. With the 3D element partition method, the cracked body can be meshed in the original mesh scheme avoiding remeshing and setting-up of joints elements. Secondly, the AVIB constitutive model based on the modified Xu-Needleman potential was derived and then was used to describe the matrix of rock mass. By the modified AVIB method, the fracture criterion contained in the bond potential was directly embedded in the constitutive model, which made it highly efficient to simulate fracture propagation. The shear propagation behaviors of embedded cracks with different normal loads were simulated. The simulation results demonstrate that the strength and propagation pattern of cracks under direct shear stress are closely related to the normal stress. Under normal tensile or lower normal compressive stress, the embedded crack propagates in shear pattern and the shear resistance increases with increasing normal stress. This conforms to the Coulomb's law. Under the intermediate normal compressive stress, the mixed (shear and tensile) failure pattern was found. Under higher normal compressive stress, compression failure could be observed and propagation mode is similar to that subjected to uniaxial compression load. The effect of the shear stress on the crack propagation decreased with normal stress increasing, the harder two joint faces relatively slip.