Experimental study on mechanical properties of similar model of fractured rock mass under biaxial loading

The deep strata in the coal mine are mainly affected by the tectonic stress field, which is mainly horizontal stress and has obvious directionality. As for the development of joints and fractures in coal measures, in order to explore the fracture characteristics and mechanical characteristics of fractured rock mass in deep coal mine, a fractured rock mass test platform was developed, and the similar models of fractured rock mass with different inclination angles were prepared. Biaxial loading tests were carried out. Based on the test results and digital image correlation technology（DIC）, the influence of joint inclination on the strength and fracture characteristics of fractured rock mass was analyzed and studied, the results show that the angle between the crack and the principal stress direction has a great influence on the peak strength of the specimen. When the angle is 30 °, the peak strength of the specimen is the lowest, and when the angle is 90 °, the peak strength is the highest. There are seven types of secondary cracks in the specimen after loading. With the increase of the inclination angle of the prefabricated crack, the failure mode of the specimen experienced the changes of compression shear failure, tension shear composite failure and compression shear failure. The secondary crack propagation experienced the changes of coplanar with the prefabricated crack, different from the prefabricated crack and coplanar with the prefabricated crack.