Naturally completely decomposed granite (CDG) soil typically exhibits strain-hardening behavior under undrained shear conditions. Nevertheless, flow-type landslides are not uncommon in CDG landfills. This paper endeavors to address the observed contradiction by conducting a case study of the 2015 Shenzhen landslides. Based on field investigations, we propose a hypothesis for the initiation and evolution of flow-type landslides in CDG landfill slopes, termed ‘clay particle argillization, mud-water migration, and static liquefaction’. This hypothesis was verified by element-scale internal erosion tests and triaxial tests, and further elucidated by microscale particle analysis. It was observed that the internal erosion-induced removal of plastic fine particles and retention of low-plasticity fine particles from CDG soil promotes the sliding and reorganization of coarse granules under shear stress, thereby increasing the soil's susceptibility to fluidization under undrained conditions. The proposed hypothesis and experimental findings provide new insights into the instability and subsequent extensive runout of CDG landfills and analogous broadly graded landslides.

中文翻译：

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细颗粒物迁移诱发的土壤流态化：来自 2015 年深圳垃圾填埋场滑坡的见解


自然完全分解的花岗岩 （CDG） 土壤通常在不排水的剪切条件下表现出应变硬化行为。尽管如此，流式山体滑坡在 CDG 垃圾填埋场并不少见。本文试图通过对 2015 年深圳滑坡事件进行案例研究来解决观察到的矛盾。基于实地调查，我们提出了一个假说，即 CDG 垃圾填埋场边坡中流型滑坡的发生和演变，称为“粘土颗粒泥化、泥水迁移和静态液化”。这一假设通过元素尺度的内腐蚀测试和三轴试验得到了验证，并通过微尺度颗粒分析进一步阐明了这一假设。据观察，内部侵蚀诱导的塑料细颗粒的去除和低塑性细颗粒从CDG土壤中保留促进了粗颗粒在剪切应力下的滑动和重组，从而增加了土壤在不排水条件下对流化的敏感性。提出的假设和实验结果为 CDG 垃圾填埋场和类似的广泛分级滑坡的不稳定性和随后的广泛流失提供了新的见解。