Study on mechanical properties and crack evolution law of thin layered slate considering soft and hard interbedded structure

Natural thin-bedded slate forms a laminated structure with soft and hard interlayers under regional metamorphism, and its mechanical properties are strongly influenced by the soft interlayers. In this paper, the effects of laminar inclination angle and soft-hard layer thickness on the strength, damage mode, and crack extension behavior of thin-laminated slate are investigated by the three-dimensional discrete element particle flow program (PFC3D). First, the microscopic parameters of the numerical simulations were calibrated based on the mechanical properties of laminated slate specimens in the field. Then, 35 cylindrical models with 7 different laminar inclinations and 5 soft laminar thicknesses were created and simulated in triaxial compression tests using the discrete particle layering construction method, considering both soft interlayers and hard rock layers. Finally, based on the numerical simulation results, the effects of different laminar inclination angles and soft interlayer thicknesses on the mechanical properties and crack generation of slate were investigated, and the fitting equations of the soft interlayer thicknesses and the strength of slate were obtained. The results of this paper have an important guiding value for the engineering construction and prevention of geologic hazards in the distribution area of thin-layered slate, and provide a key scientific basis for related engineering design, construction and safety assessment.