Repetitive shear mechanical properties and constitutive model of jointed sandstone under heat-wet cycle

Wudongde, Baihetan and other large reservoirs are located in the typical dry and hot valley of the Jinsha River. The rock and soil mass in the fluctuating zone of the bank slope are affected by the annual large rise and fall of the reservoir water level and the small frequent changes in the flood season, as well as the high temperature and low humidity climate conditions in the dry and hot valley, regional high-frequency earthquakes and reservoir earthquakes. Based on the previous research on water rock interaction, a study was conducted on the degradation of repeated shear mechanical properties of jointed sandstone under the influence of thermal and wet cycles, taking typical bank slope jointed sandstone in the Wudongde reservoir area as the research object. Research has shown that: ① under the action of heat-wet cycles and repeated shear, the shear strength, shear stiffness, shear expansion value, and yield point shear displacement of jointed sandstone exhibit a "fast-slow-stable" deterioration trend. Among them, the degradation amplitude is significant in the first three cycles, accounting for nearly 70% of the degradation rate. The degradation rate slows down within 3 to 8 cycles, and stabilizes after 8 cycles; ② Compared to the dry-wet cycle, the heat-wet cycle has a greater impact on rock porosity and longitudinal wave velocity, and the connection between rock particles is more susceptible to damage at higher temperatures; ③ According to the characteristics of shear stress shear displacement curve, the constitutive model described by Goodman model and Clough-Duncan Hyperbola model was established, and the model curve was in good agreement with the test results. The research results and methods can provide reference for the stability analysis of the rocky bank slope in the dry hot valley reservoir.