Mechanisms of rill sidewall collapse on slopes under coupled freeze-thaw and dry-wet cycling

The coupled freeze-thaw and wet-dry cycles significantly exacerbate the deterioration of soil mechanical properties, critically compromising the stability of rill sidewalls on slopes. Current research remains insufficient in elucidating the mechanisms underlying composite erosion processes linked by these coupled effects. This study investigates the deterioration of soil mechanical properties under coupled freeze-thaw and wet-dry cycles, and employs a self-developed slope erosion testing apparatus to conduct rainfall-induced slope erosion modeling experiments, thereby revealing the collapse mechanisms of rill sidewalls under these conditions. Key findings include: both freeze-thaw and wet-dry cycles adversely affect soil internal friction angle and cohesion, with established quantitative relationships between these mechanical parameters and the number of coupled cycles; rainfall triggers rill sidewall collapse, leading to abrupt particle loss that rapidly peaks; through theoretical analysis and experimental data, we propose a computational method that accurately predicts crack initiation locations at rill sidewall crests and determines critical instability thresholds. These findings provide a scientific basis for quantitative analysis of composite slope erosion processes and the development of targeted mitigation measures.