Experimental Study on the Mechanical Behavior Evolution of Cohesive Soils under Wet-Dry Cycling

Wetting-drying cycles induce structural changes and fissure development in cohesive soils, triggering geological disasters such as landslides. This study employs direct shear tests and fissure observations to elucidate the mechanical evolution patterns of cohesive soils with different initial dry densities during wetting-drying cycles. The key findings are as follows: 1) The shear strength decreases with an increasing number of wetting-drying cycles, with the most significant reduction occurring in the first cycle; 2) Theτ-S (shear stress-normal stress) curve exhibits a peak starting from the second wetting-drying cycle, and the peak value intensifies with subsequent cycles; 3) The surface fissure ratio is positively correlated with both the number of wetting-drying cycles and the initial dry density; 4) After multiple wetting-drying cycles, the shear strength of shallow soil layers tends to converge, and the influence of initial dry density diminishes.