Study on the Mechanical Properties and Energy Evolution Law of Unloading of Jointed Sandy Slate

In order to reveal the mechanical properties and energy evolution law of unloading failure of sandy slate under different joint types, the conventional triaxial compression test and unloading test were carried out by using RMT-150C rock mechanics test system. The bearing capacity, failure mode and energy evolution characteristics of jointed slate were discussed, and the damage variable was proposed based on dissipation energy. The results show that: (1) The joint type has a great influence on the bearing capacity of the specimen, and the peak strength is mainly manifested as no joint specimen > double joint specimen > single joint specimen; (2) The macroscopic failure mode of the specimen is mainly shear failure. The unloading effect will cause the single joint specimen to produce transverse cracks at the joint end, while the double joint specimen will produce penetrating cracks. (3) The total energy and dissipated energy show the law of single joint specimen < double joint specimen < jointless specimen, and the damage variable (damage degree) of the specimen is also the same. The test results are helpful to understand the mechanical behavior and energy evolution characteristics of different joint types of rock, and provide the necessary basis for the structural stability of rock mass under unloading confining pressure.