Progressive Failure Characteristics of Strain-Softening Subgrade Slopes Based on the Local Slip Point Safety Factor

Résumé fourni par la source

In Southwest China’s mountainous areas, subgrade slopes are prone to strain softening and progressive failure under rainfall conditions. To clarify the failure mechanism and evaluate slope stability, this study adopts the displacement-isosurface-based local slip point safety factor method incorporating element stress–strain relationships. Its applicability to strain-softening slopes is examined by comparing the calculated low-value zone of the local slip point safety factor with the observed slip surface of a weak-interlayer subgrade slope. Numerical analyses are conducted to investigate the progressive failure behavior of subgrade slopes, considering both global strain softening and weak-interlayer softening. The method is subsequently applied to a case study of a subgrade slope supported by anti-slide piles in Yunnan Province. The results indicate that for strain-softening subgrade slopes, progressive failure manifests as typical retrogressive sliding. Due to stress concentration at the slope toe, strength degradation initiates in this region and progressively extends upward, forming a potential slip zone. This eventually leads to the instability of the upper slope. Thinner weak interlayers and steeper dip angles accelerate the development of retrogressive failure, while multi-level bench configurations can delay its progression. Sensitivity analysis shows that, within the examined range, the plastic shear strain threshold mainly affects the degree and progression of strength degradation but has limited influence on the principal distribution of the local slip point safety factor. After replacing the weak interlayer, the risk of retrogressive failure is significantly reduced, and the local slip point safety factor meets engineering design requirements. By jointly examining the strength degradation coefficient and local slip point safety factor, this study characterizes the spatial evolution of retrogressive failure and supports reinforcement design for strain-softening subgrade slopes.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.