Experimental study on mechanical properties of multi-layered rock mass and statistical damage constitutive model under hydraulic-mechanical coupling

The triaxial compression tests of multi-layered rock mass samples prepared from the laboratory were carried out by using the rock servo-controlled triaxial rheological test system, and the mechanical properties of multi-layered rock mass are studied. According to the test results, the deformation characteristics and failure modes of multi-layered rock mass samples are analysed. The relationship between layers and mechanical parameters of rock mass samples is discussed. The results show that the peak strength and the peak strain increases along with the increase of confining pressure. Failure forms of multi-layered rock mass samples include monoclinic shear failure, tension crack failure, and interfacial shear slip failure. The more layers, the more broken the samples are. The more layers there are, the smaller the peak strength and the cohesive force of multi-layered rock mass samples are. Moreover, there is an exponential relationship between the internal friction angle and the number of layers. Based on the test results, considering the weakening of the mechanical properties of rock mass by the number of layers, the statistical damage constitutive model of the rock mass under hydraulic-mechanical coupling is established and verified. The results indicate that the model fits the experimental data well.