Shear creep characteristics and constitutive model of hidden non-persistent joints

The joints control the boundary of the rock slope instability. A large number of joints in the natural world are not completely persistent, and are hidden inside the slope. The study on the hidden non-persistent joints is of great significance for revealing the failure mechanism and stability of the slope. The rock specimens with natural hidden non-persistent joints are difficult to sample and cannot be replicated in large quantities. A model experiment on the rock mass with hidden non-persistent joints is made in laboratory, which is similar to the reality. Based on the uniaxial compression tests and direct shear tests, the shear creep tests and creep characteristics of rock mass with hidden non-persistent joints are carried out by using the YZJL-300 rock shear rheometer. According to the creep test results, based on the creep stage characteristics and previous researches on the creep constitutive model, a new constitutive model for the shear creep damage is established by introducing a non-linear viscous accelerating element and a material damage variable suitable for joints. Because the rock mass is in the three-dimensional stress condition under actual conditions, in order to be better applied to the actual engineering, the three-dimensional state of the constitutive model is generalized. The obtained creep test curve is identified by the L-M algorithm and global optimization method to solve the model parameters. By identifying and comparing the test results and model fitting results, the new constitutive model can better reflect the creep characteristics of rock mass.