Discrete Element Study on Mesoscopic Shear Mechanical Behavior of Fully Weathered Coastal Red Sandstone Considering Different Rock Mass Stability Grades

The macro parameters such as cohesion and internal friction angle are usually measured on experimental test. The macro shear mechanical behaviors are determined by mesoscopic shear mechanical behaviors, which are difficult to be measured accurately on experimental test. This paper aims to study the mesoscopic shear mechanical behaviors of fully weathered coastal red sandstone (FWCRS) such as the force and displacement of rock particles, the force chain network, the microcracks and the coordination number, which can be systematically studied by discrete element software such as Particle Flow Code (PFC). This paper established models characterizing FWCRS with different rock mass stability grades by results obtained on experimental tests, and investigated the differences of their mesoscopic shear mechanical behaviors. The results show that the mesoscopic shear mechanical behaviors of FWCRS can be characterized by performing direct shear simulation and the differences among different rock mass stability grades were also revealed. As the stability increases from grade 1 to grade 5, the shear stiffness increases, the number of microcracks reduces by 48.07%, and there are significant differences in properties of shear band, development of microcrack, the coordination number and the force chain network. The research results can provide reference for the related research such as the evolution of mesoscopic shear mechanical behaviors in the failure process of rock mass in FWCRS and similar strata.