Study on mechanical properties of sand-mudstone interbedded rock mass under different layer thickness ratio-dip angle conditions

To clarify the anisotropic mechanical properties of sand-mudstone interbedded rock, the mechanical parameters of sandstone and mudstone were obtained through laboratory experiments. The microscopic parameters of sandstone and mudstone were calibrated using PFC 2d software. Subsequently, numerical triaxial compression tests on interbedded sand-mudstone specimens were conducted under different thickness ratios and dip angles. The influence of thickness ratio and dip angle on the mechanical properties and deformation failure characteristics of interbedded sandstone and mudstone samples was analyzed. The research results indicate that: (1) Under the same layer thickness ratio conditions, with an increase in the dip angle of the rock layers, the compressive strength and elastic modulus exhibit a trend of initially decreasing and then increasing. (2) The abrupt change point in the number of cracks during sample loading corresponds to the elastic, plastic, and failure characteristic points on the stress-strain curve. (3) Under the influence of the thickness ratio and dip angle of rock layers, the failure modes of sandstone mudstone interbedded rock samples can be divided into three types: tensile shear failure, shear slip failure along the bedding plane, and composite failure where both slip failure and tensile shear failure coexist.