Investigation on fracture mechanism of layered slate: experiment and beam-particle method

The layered rock masses with structural planes are widely distributed, among which the transverse isotropy caused by the bedding structural plane has a great influence on the stability of the slope and surrounding rock. Construct a beam-particle model (BPM) to reveal the layered slate fracture characteristics is of great significance. This paper takes the layered carbonaceous slate of the Muzhailing tunnel in Shanxi as the research specimens, carries out the Brazilian split test and uniaxial compression test of the layered slate with different bedding inclination angles, and conducts out a systematic numerical analysis based on the BPM solver. The test and numerical results show that: (1) In the Brazilian split test, the load–displacement curve of the layered slate has the development trend of the initial stage, the rock specimens compaction, nearly linear elasticity, and finally complete collapse. As the bedding inclination angle changes from 0 ∘ to 90 ∘ , the tensile strength of slate decreases successively. (2) In the uniaxial compression test, when the bedding inclination angle is 0 ∘ and 90 ∘ , the compressive strength is greater, and the bedding inclination angle is 30 ∘ , 45 ∘ and 60 ∘ , the compressive strength is small and the value is close, showing a “U”-shaped change as a whole. (3) With the change of bedding inclination angle and the comprehensive influence of matrix and bedding, the split failure mode of layered slate is complex and changeable, and roughly presents split tensile failure, shear slip failure and comprehensive tensile shear failure. (4) Through the comparative analysis of test load–displacement response and failure mode, the BPM solver can better reproduce the split evolution process of layered slate under different bedding inclination angles, and prove the robustness and stability of the program. The BPM solver can provide a new numerical research method for the widespread engineering practice of layered rock masses.