Damage effects and model for jointed rock mass under water-rock interaction and repeated shear sequence

In the process of reservoir impoundment, some bank slopes show an obvious step-type deformation trend, and the rock mass in the water-level-fluctuation zone is under the action of periodical fluctuation of reservoir water level and periodic repeated shear sequence. Based on this, the water-rock interaction tests on the jointed rock mass are designed, and the repeated shear tests are carried out in different water-rock interaction periods. The results show that: (1) Under the effects of water-rock and repeated shear sequence interaction, the shear mechanical properties of jointed rock mass deteriorate obviously, while the shear strength, shear stiffness and JRC exhibit the degradation trend of "first steep then slow". In comparison, the former six cycles of degradation trend are obvious, and the greater the normal stress, the more obvious the degradation trend. (2) The deterioration trend of the shear strength caused by the repeated shear is particularly obvious in the initial state, and then decreases rapidly with the increase of the water-rock interaction cycle. The deterioration trend of the shear strength caused by the water-rock interaction is obvious in the first six cycles, and then tends to be flat. (3) The damage area of joint surface wall is divided into the water-rock damage area, water-rock and repeated shear sequence damage area. The JRC-JCS shear strength model is modified, and the verification analysis shows that the calculated values by the modified model are in good agreement with the test results. The relevant research methods and results may provide a good reference for the performance degradation analysis of jointed rock mass in the water-level-fluctuation zone of reservoir bank slopes.