Soil shear strength is a critical mechanical property governing the stability of collapsing walls in Benggang erosion, a severe form of land degradation in the granitic hilly regions of southern China. While its importance is recognized, a systematic comparison of the driving mechanisms behind shear strength indicators between collapsing walls and intact, non-collapse soil profiles has been lacking. This study addresses this gap by integrating direct shear testing, complex network analysis, and partial least squares-structural equation modeling (PLS-SEM). Quantitative analysis confirmed significantly lower shear strength in collapsing walls relative to non-collapse profiles, exhibiting reductions of 32.90% in cohesion force and 8.13% in the internal friction angle. Complex network analysis further revealed a less complex and more fragmented interaction network among soil properties within the collapsing walls, characterized by fewer connections and slower information transmission. Mechanistic insights from PLS-SEM identified basic chemical properties as the dominant direct factor influencing shear strength indicators changes, whereas physical properties exerted their effects indirectly by modulating basic chemical properties and iron–aluminum–manganese oxides. This study conclusively demonstrates that the degradation of soil shear strength in collapsing walls stems primarily from the fundamental alterations in soil properties and the disruption of their synergistic interactions, providing a novel mechanistic framework for understanding and predicting Benggang evolution.
Zhang et al. (Fri,) studied this question.