Influence of hydraulic-mechanical coupling and dry-wet cycle effect on surficial layer stability of residual soil slopes

During rainfall infiltration, soil suction decreased and volume changed significantly. Since the natural shallow soil was under the influence of seasonal climate changes for a long time, numerical analysis of the influence of hydraulic-mechanical coupling and dry-wet alternation on the stability of shallow residual soil slopes was carried out. The temporal and spatial evolution law of pore water pressure, wetting front and safety factor of shallow soil slopes were analyzed deeply, then, the failure mechanisms of soil slopes under hydraulic-mechanical coupling and alternating dry-wet conditions were further discussed. Results show that with the increase of dry-wet cycles, the migration velocity of wetting front and pore water pressure increased more quickly, and the slope was more unstable under hydro-mechanical coupling analysis. At the early stage of the dry-wet cycle, the infiltration of rainwater would easily cause the groundwater level to rise, and the slope might lose its stability due to the increase of positive pore water pressure. In the later stage of dry-wet cycle, the rapid advance of wetting front accelerated the rapid loss of matrix suction and the decrease of soil strength, the safety factor of slope was significantly reduced and the time of failure was shorter. Therefore, the safety factor (local minimum) at the wetting front could be used as the critical value to control the long-term stability of the slope.