Fracture evolution and failure mechanism of rock-like materials containing cross-flaws under the shearing effect

Abstract

Shear failure of rock masses along discontinuities is one of the dominant failure modes of underground tunnels and rock slopes. In this paper, the shear fracture evolution and failure mechanism of rock-like materials containing cross-flaws are first reported based on a developed CZM-FEM method. The laboratory uniaxial compression and corresponding numerical tests were initially performed to acquire the mechanical parameters of rock-like materials. Subsequently, the direct shear test of rock-like materials containing two sets of cross-flaws was conducted, the effect of the main flaw and secondary flaw angles were considered. At last, the mechanical properties and fracture behaviors, and the coalescence mechanism were investigated and concluded. The results indicate that four typical stages are observed during the shearing process of rock-like materials with cross-flaws, which are the linear elastic stage, crack strengthening stage, plastic softening stage, and residual strength stage, respectively. Note that the mechanical properties (i.e., peak, residual shear strength, and the crack initiation stress) and cracking behaviors are strongly dependent on the angles of the main and secondary flaws as well as the loading conditions (i.e., shear rates and constant applied normal stresses). In addition, the coalescence mechanism of rock bridge between the two cross-flaws can be classified into three types, which are the mixed shear tensile-tensile damage, shear-tensile damage, and tensile damage, respectively; Similarly, the coalescence paths can also be identified as three types, respectively, the connection between the main flaw and the secondary flaw, linkage by the two main flaws, and the penetration dominated by the coalescence of the main flaw and the secondary flaw.