复杂层状堆积体降雨渗透模型试验研究

Model experimental study on rainfall infiltration of complex layered colluvial deposits

摘要

为揭示降雨条件下复杂层状堆积体边坡的失稳机制及其影响因素，以查甫层状堆积体边坡为地质原型，构建几何相似比为1∶100的缩尺物理模型，开展降雨条件下的物理模型试验。分析试验过程中的斜坡变形演化过程及含水率、孔隙水压力与基质吸力的动态变化规律，揭示了渗透性差异对层状堆积体失稳破坏的影响机制。研究表明，渗透性差异主导渗流路径分异演化，低渗透性粉土层受表层滞水软化诱发陡坎拉裂，高渗透性卵石土层则由于逆向渗流作用引发结构重组与蠕滑变形，表层径流冲刷加剧冲蚀剥落。层间渗透系数差异导致非均匀渗流动态响应，表现为低渗透层滞水区孔隙水压力激增，高渗透层界面处饱和区逆向扩展。孔隙水压力累积、基质吸力衰减与细颗粒迁移形成协同效应，加剧水力劣化进程，最终触发后缘拉裂与前缘蠕滑协同发展的“蠕滑－拉裂”灾变模式。层状堆积体灾变机制呈现“浅表滞水软化-内部渗流重组-径流剥蚀破坏”的复合演化特征，渗透性差异通过非均匀渗流与水力劣化的耦合作用控制边坡失稳全过程。

Abstract

To investigate the failure mechanisms and influencing factors of complex layered colluvial slopes under rainfall conditions, a scaled physical model with a geometric similarity ratio of 1∶100 was constructed based on the Cha’pu layered colluvial slope as a geological prototype. A rainfall infiltration experiment was conducted using this physical model. The deformation process of the slope and the dynamic changes in volumetric water content, pore water pressure, and matrix suction during rainfall were analyzed, revealing the influence mechanism of permeability differences on the instability and failure of layered deposits. The results show that permeability differences control the evolution of seepage paths. In the low-permeability silty soil layer, water ponding at the surface causes softening and tensile cracking at steep slopes. In contrast, the high-permeability gravelly soil layer experiences structural reorganization and creep deformation due to reverse seepage. Surface runoff further intensifies erosion and stripping. The contrast in permeability coefficients between layers leads to non-uniform seepage dynamic responses. Pore water pressure rapidly increases in the water-retaining zones of low-permeability layers, while the saturated zones at the interfaces of high-permeability layers expand reversely. The synergistic effect of pore water pressure, reduction in matrix suction, and fine particle migration exacerbates the hydraulic degradation process, ultimately triggering a “creep-tensile cracking” catastrophic mode in which trailing edge tensile cracking and leading edge creep develop in tandem. The failure mechanism of layered colluvial deposits exhibits a composite evolution characteristic, surface water ponding and softening, internal seepage redistribution, and runoff-induced erosion. Permeability differences govern the entire slope failure process through the coupling effect of non-uniform seepage and hydraulic degradation.

关键词

层状堆积体 / 降雨 / 物理模型试验 / 渗透机理 / 成灾模式

Key words

layered colluvial slopes / rainfall / physical model experiment / infiltration mechanism / failure mode

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基金资助

国家自然科学基金项目(42293353)

国家自然科学基金项目(42293350)