Abstract: In order to study the mechanical properties and failure modes of fractured shale under the seepage stress, the rock failure process analysis system RFPA2D-flow was used to establish 7 groups of shale models with prefabricated fractures at different angles and the fracture process was numerically simulated. The results show that the fracture process of the shale can be divided into three stages: progressive linear deformation, yield deformation and complete failure. Due to the existence of fractures, the elastic modulus and compressive strength of the shale show distinct anisotropic characteristics and the final fracture mode of the sample can be divided into four types: slash-type, X-type, λ-type and collapse-type. For the crack distributions under different bedding inclinations, the fracture of the shale sample under the coupled percolation-stress is mainly tensile failure accompanied by shear failure, and the test shows that the shear failure of the sample is most serious when α =90°. These results have important implications for shale exploitation.

Key words: percolation-stress coupling, numerical simulation, shale fracture anisotropy, rupture process