Effects of water migration-induced softening on the stability of soil-rock slopes with irregular rock block rotation behavior

To assess the effects of water-induced softening on slope stability, soil-rock slopes with different major axis inclinations of irregular rock blocks were generated using a stochastic method based on functional distribution. More than 4200 2D stability analyses were performed using strength reduction limit analysis method. For each kind of water-induced softening condition and major axis inclination, the different rock block arrangements had been made. The safety factor and shear dissipation results indicate that the rock block’s major axis inclination have a significant impact on slope stability, even as soil strength continuously decreases. Under the different softening conditions caused by water migration, slopes are most susceptible to failure when the soil throughout the whole soil-rock mixture is softened. In particular, when the soil at the base of the soil-rock mixture softened, a shear sliding zone develop from the slope toe along the contact surface. Furthermore, as soil strength continues to degrade, both an increased softening thickness and a higher volumetric rock block proportion accelerate the rate of slope stability reduction. The impact of increasing softening thickness on slope stability is primarily governed by the soil above the contact surface. It is also noteworthy noting that in slopes with a high volumetric rock block proportion, repeated cycles of water-induced softening leads to a significant loss of soil particles from the structural skeleton. This results in a more rapid decline in slope stability compared to slopes with a lower volumetric rock block proportion.