An Implementation Method of Shear Plane Fracture of Multi-Crack Rock Under Compression-Shear Loading

Taking the parallel multiple cracks rock as research object, a clamp to impose compression and shear loading was designed. Different lateral pressure can be adjusted by the clamp to achieve cracking angle's control and the shear plane fracture can be obtained. It can reveal the failure mechanism of Mode II fracture under combined loading. The Mode II stress intensity factor was calculated by finite element method and the Mode II fracture toughness calculation formula was derived. Numerical calculation and experimental results show that the tensile stress in the crack tip may be restrained when the lateral pressure imposed by clamp reaches a certain value. However, the lateral pressure must be restricted in a proper range. The specimen might be crushed by too large compression loading. The tested Mode II fracture toughness of sandstone is about 2-3 times to the Mode I fracture toughness. It is a effective way to achieve true Mode II fracture by applying compression and shear loading straightly.