Creep of clayey soil induced by elevated pore-water pressure: Implication for forecasting the time of failure of rainfall-triggered landslides
Creep of clayey soil induced by elevated pore-water pressure: Implication for forecasting the time of failure of rainfall-triggered landslides
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DOI：
10.1016/j.enggeo.2021.106461
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发表时间：
2021-11
影响因子：
7.4
通讯作者：
Chengrui Chang;Gong-hui Wang
中科院分区：
文献类型：
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作者：
Chengrui Chang;Gong-hui Wang
人们提出了许多模型来预测滑坡破坏的时间，其中Voight模型（Ω´= A Ω̇ α）得到了广泛的应用。由加速运动定义的控制参数 α 和 A 的值代表材料失效之前的运动学行为。然而，由于关键参数（α 和 A）未知，使用该模型进行故障时间预测仍然难以实现。为了检查这两个参数的性质及其物理背景，我们对粘土进行了环剪试验，通过两种不同的方法重现三次蠕变：孔隙水压力控制方法用于模拟降雨期间孔隙水压力升高导致滑坡的引发过程，以及剪切应力控制方法通常用于研究粘土的蠕变行为。通过检查孔隙水压力控制试验中观察到的蠕变行为，我们发现速度和加速度之间存在三阶段对数线性关系。样品在第一阶段表现出剧烈的膨胀和短剪切位移，并且在随后的两阶段随着剪切位移的进一步进展，膨胀减小。第一阶段较小的α值在第三阶段增加到另一个较大的值。这种变化可能是由于主要剪切机制的变化造成的，即在第一阶段，观察到的蠕变位移是由相对较宽的剪切区内普遍的晶粒重新排列引起的，而在接下来的两个阶段中，它可能是由于沿着滑动表面的剪切区变窄的区域内更局部的晶粒滑移引起的。相反，在剪应力控制测试中没有发现α值或样品高度的明显变化。在我们的测试中，孔隙水压力或剪切应力的增加率对 α 值的影响并不明显。这些结果为理解渐进式失效过程和失效时间预测的 Voight 模型提供了进一步的信息。降雨引发的滑坡的破坏时间预测可能从根本上来说是困难的，因为α值可变，体积变化复杂，并且涉及多种操作剪切机制。
Many models have been proposed to forecast the time of failure of landslides, among them the Voight model (Ω¨= A Ω ̇ α) has been widely used. Values for controlling parameters of α and A, defined by accelerating movement, are representative of kinematic behavior prior to material failure. Nevertheless, due to the unknowns in the key parameters (α and A), failure-time forecast using this model remains elusive. To examine the nature of these two parameters and their physical background, we conducted ring-shear tests on clayey soil to reproduce tertiary creep through two different approaches: a pore-water pressure-controlled approach to simulate the initiation process of landslides resulting from elevated pore-water pressure during rainfall, and a shear-stress-controlled approach often used in studies of the creep behavior of clayey soils. By examining the creeping behavior observed in the pore-water pressure-controlled tests, we found a 3-stage log-linear relationship between velocity and acceleration. The sample showed drastic dilation with short shear displacement in the first stage, and the dilation decreased in the subsequent two stages with further progress of shear displacement. The smaller value of α in the first stage increased to another value which was larger in the third stage. This variation might result from changes in the dominant shear mechanisms, ie, in the first stage the observed creeping displacement results from pervasive grain realignment within a relatively wide shear zone, while in the following two stages, it may arise from more localized grain slip within a narrowing domain of shear zone along the sliding surface. In contrast, no evident variations in α value or sample height were found in the shear-stress-controlled tests. The effects of increasing rate of pore-water pressure or shear stress on the value of α were not pronounced in our tests. These results provide further information for understanding the progressive failure process and the Voight model of failure-time forecast. The failure-time forecast of rainfall-triggered landslides could be fundamentally difficult because of a changeable α value with the intricate volumetric variation and a diverse range of operating shear mechanisms involved.