Study on degradation mechanisms of sandstones joints in the hydro-fluctuation zones of dry-hot valley bank slopes

Since the Wudongde reservoir area is located in the dry-hot valley area，the rock mass in the hydro-fluctuation zone is in the heat and wet cycle state. In order to study the damage evolution mechanism of sandstone joints under the action of the heat and wet cycle，the heat and wet cycles and repeated shear tests were designed and conducted on sandstone joints to analyze the shear resistance，the joint surface morphology characteristics，and the evolution law of energy parameters. The research results indicate that：(1) within 12 heat and wet cycles，the shear mechanical parameters and dimensional morphology parameters of sandstone joint surfaces show a degradation pattern of first rapid decrease and then slow stabilization. Among them，the degradation amplitude of each parameter in the first 3 cycles is significantly larger，and then the degradation trend gradually slows down，and tends to stabilize after 8 cycles. (2) As the heat and wet cycle increases，the total energy and dissipated energy of sandstone joints gradually decrease during the shear process，and their changing trend is consistent with the mechanical parameters. In comparison，the change in elastic energy is relatively small，and the trend in dissipated energy is obvious. (3) The shear performance damage mechanism of sandstone joints under the heat and wet cycle includes three aspects. Firstly，the damage effect of the heat and wet cycle on rock wall strength and joint surface morphology. Secondly，the change of joint surface morphology caused by repeated shear and the damage effect of rock mass within a certain depth range of rock wall. Thirdly，the mutual promotion effect of the heat and wet cycle and repeated shear sequence on joint surface damage. The relevant methods and results can provide a good reference for the heat and wet cycle damage degradation analysis of rock joints in the dry-hot hydro-fluctuation zone of the reservoir bank slope. © 2024 Academia Sinica. All rights reserved.