Strength Deterioration Model of Lushi Swelling Rock under Wetting–Drying Cycles and Its Application in High Slopes with Rainstorm Conditions

To study the degree of strength parameter deterioration (DSPD) of Lushi swelling rock in the high slope area under wetting–drying cycles, 114 samples are remodeled. Wetting–drying cycle and triaxial tests are conducted to comprehensively analyze the influence of dry density, wetting–drying cycle path, and number of wetting–drying cycles on the strength deterioration characteristics of Lushi swelling rock. Using the fitting analysis and function superposition methods, the DSPD model of Lushi swelling rock under wetting–drying cycles is established, which considers the previous four influencing factors. The influence of the DSPD of Lushi swelling rock on the stability of high slopes under rainfall seepage and circulation conditions is studied. Lushi swelling rock exhibits significant strength deterioration characteristics under wetting–drying cycles. The overall DSPD for cohesion is higher than that of the internal friction angle. Under rainstorm conditions, strength deterioration leads to a shallower depth of the critical slip surface of the slope and a smaller safety factor. After eight rounds of rainfall seepage and circulation, the safety factor gradually decreases by approximately 14%–28%. This study provides and verifies the DSPD model of Lushi swelling rock under wetting–drying cycles, and the results could provide a basis for disaster prediction and the optimization design of swelling rock slopes.