Abstract: Cross crack, as one of the common forms of fractured rock mass, the overlapping geometry properties affect the expansion damage of rock mass and the catastrophe mechanism. Taking rock samples containing a single group of cross fractures as the research object, the mechanical properties and propagation failure laws of rock samples affected by the dip angles of primary and secondary fractures are emphatically discussed. The results show that: when the inclination angle of the primary fracture is less than or equal to 45°, the horizontal projection length of the primary fracture is larger than that of the secondary fracture, and the inclination angle of the primary fracture has a great influence on the peak strength and elastic modulus of the rock sample. When the inclination angle of the primary fracture is greater than 45°, the horizontal projection length of the secondary fracture is larger, and the inclination angle of the secondary fracture has a great influence on the peak strength and elastic modulus of the rock sample.The macroscopic crack propagation on the surface of rock samples is mainly characterized by the cracks at the primary crack tip and the secondary crack tip, while the far-field cracks and surface spalling are less.The failure mode of rock samples is controlled by the horizontal projection length of the primary and secondary fractures, that is, when the projection length of the primary fracture is larger than the secondary fracture, the failure is controlled by the primary fracture. Otherwise, it is controlled by the secondary fracture.

Key words: cross crack, crack propagation, failure mode