Dispersive soils are susceptible to rapid disintegration upon contact with water and have been implicated in engineering slope failures. However, a refined characterization of their response to rainfall remains insufficient. In this study, we investigated the evolution, peculiarity, and mechanisms of hydraulic failure in dispersive soil under artificial rainfall events conducted in a laboratory setting. Morphological changes, runoff properties, and soil–water interaction during and between rainfall events were observed, monitored, and analyzed. Results reveal that erosion cavities formed rapidly under a low intensity of 20 mm/h. We noted that the dominant erosion type then shifted from rill to sheet erosion when surpassing 60 mm/h. The existence of flaky debris and minuscule scarps signaled the repeated formation and rupture of the surface sealing layer, which prevented erosion of deeper soil layers. Moreover, runoff gradually roughened the micro topography of the slope by transporting clay particles. The sediment concentration of runoff fluctuated most dramatically during the first three rainfall trials. The attenuation of runoff electrical conductivity during a single rainfall event suggested the leaching of soluble salts. However, the salts migrated towards the surface during evaporation, which increased dispersion risks. Surprisingly, only 3% of soil particles were eroded in the entire test, of which 93% originated from the slope bottom platform and the remaining 7% from the slope surface. This indicated that compaction operation on dispersive soil can reduce the degree of rainfall-induced failure. The dynamics of soil water content reflected the weak permeability of compacted dispersive clay and also highlighted that the vulnerable areas were in the middle and lower parts. In summary, the failure is manifested in erodibility, superficiality, retrogressive nature, gradual progression, and recurrence. The findings acquired contribute to the understanding of dispersive soil behavior under rainfall stresses, offer insights into the mechanisms driving slope degradation and potential strategies for mitigating erosion risks.

中文翻译：

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多次降雨条件下分散土填土边坡形态演变和水文响应模型试验研究


分散性土壤在与水接触时容易迅速崩解，并且与工程边坡破坏有关。然而，对它们对降雨的反应的精确描述仍然不够。在这项研究中，我们研究了在实验室环境中进行的人工降雨事件下分散土壤水力破坏的演变、特性和机制。观察、监测和分析了降雨事件期间和降雨事件之间的形态变化、径流特性和土壤-水相互作用。结果显示，在 20 mm/h 的低强度下，侵蚀空洞迅速形成。我们注意到，当超过 60 mm/h 时，主要侵蚀类型从沟状侵蚀转变为片状侵蚀。片状碎屑和微小的断层的存在标志着表面密封层的反复形成和破裂，从而阻止了更深的土壤层的侵蚀。此外，径流通过输送粘土颗粒逐渐使边坡的微地形变得粗糙。在前三次降雨试验期间，径流的沉积物浓度波动最大。在单次降雨事件期间径流电导率的衰减表明可溶性盐的浸出。然而，盐在蒸发过程中向表面迁移，这增加了分散风险。令人惊讶的是，在整个测试中只有 3% 的土壤颗粒被侵蚀，其中 93% 来自坡底平台，其余 7% 来自坡面。这表明在分散性土壤上进行压实操作可以降低降雨引起的破坏程度。 土壤含水量动态反映了压实分散粘土的弱渗透性，也突出了脆弱区域位于中下部。总之，失败表现为易侵蚀性、肤浅性、倒退性、逐渐进展和复发。获得的研究结果有助于理解降雨胁迫下土壤的分散行为，为驱动边坡退化的机制和减轻侵蚀风险的潜在策略提供了见解。