The paper analyses the dynamic behaviour of a class of landslides characterised by a well-defined failure surface where shear strains accumulate. The subject goes beyond the common concepts of safety factor and static analysis, and discusses procedures to identify the velocity and runout, once stability is lost. Three initial case histories serve to highlight the relevance of predicting the motion after failure. These cases and a few others discussed in the paper help to connect the theoretical developments with their relevance in practice. The following landslides receive attention in the paper: Pampaneira, Cortes, Aznalcóllar, Vallcebre, Selborne, Vajont and Canelles. Existing publications describe all of them in some detail. These landslides illustrate the following phenomena: creeping motion, first-time failures, rapid sliding and the transition from slow to very rapid motion. These phenomena are present in the concept and organisation of the paper. Simple geometries (planar, double block) facilitate the description of the basic physics but are also capable of delivering useful solutions and deep understanding. In a second stage, the simple sliding cases evolve into continuum analysis. The material point method (MPM) offered the possibilities of approaching arbitrary geometries and removed a main limiting assumption of simple cases, namely the ‘a priori’ knowledge of the failure mechanism and its subsequent propagation. Two well-documented cases of progressive failure in brittle, high-plasticity, overconsolidated clays (Aznalcóllar and Selborne) provided useful data to check the capabilities of the MPM analysis to predict correctly the internal development of shearing surfaces and the observed runout. The method also provides information regarding the transition from an essentially ‘static’ behaviour to an accelerated displacement. A sensitivity analysis, inspired by the Selborne case, resulted in an interesting relationship between runout and soil brittleness. Rate effects on friction angle explain the creeping behaviour of landslides. Changing velocities of Vallcebre slide under a time history of pore water pressures provided a validation exercise for a simple modelling approach. However, friction laws do not easily explain the sudden acceleration observed in landslides such as Vajont. Previous work to explain the rapid acceleration and fast motion observed in some landslides rely on heat-induced pore pressurisation of the sliding surface. Further work introducing a double wedge for Vajont landslide stressed the relevance of shear band thickness and, in particular, the soil permeability. A generalisation of the involved thermo-hydro-mechanical (THM) formulation, by way of MPM, met the difficulty of solving the inconsistent results deriving from the mesh-size control of the shear band thickness. The solution was to embed shear bands, with a reasonable thickness, in the material points describing the soil matrix. This approach successfully reproduced the known Vajont after-failure motion. The model provided estimations of the internal shearing of the sliding rock mass, the temperature increase of the sliding surface and its transient excess pore pressures. A final section describes the close relationship between the creeping motion of a landslide and its eventual evolution towards a rapid phenomenon. A simple planar slide provided a set of dimensionless parameters governing the interaction. Strain rate effects on friction explained the creeping part of the problem. The paper describes a generalised approach to arbitrary geometries by means of MPM formulation. Canelles landslide was useful to discuss the merits and limitations of predictions based on the absence or presence of creeping and THM physics of the formulation and their possible combinations.

中文翻译：

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滑坡的触发与运动

本文分析了一类滑坡的动态行为，该滑坡的特征是具有明确定义的破坏面，剪切力在此积聚。该主题超越了安全系数和静态分析的通用概念，并讨论了一旦失去稳定性，识别速度和跳动的程序。最初的三个案例历史突出了预测失败后动作的相关性。这些案例以及本文中讨论的其他案例有助于将理论发展与其在实践中的相关性联系起来。下列滑坡在本文中受到关注：潘帕内拉（Pampaneira），科尔特斯（Cortes），阿兹纳尔科拉尔（Aznalcóllar），瓦勒布雷（Vallcebre），塞尔伯恩（Selborne），瓦琼特（Vajont）和卡内莱斯（Canelles）。现有出版物详细描述了所有这些出版物。这些滑坡说明了以下现象：蠕动，初次破坏，快速滑动以及从慢速运动到非常快的运动的过渡。这些现象存在于本文的概念和组织中。简单的几何形状（平面，双块）有助于描述基本物理原理，但也能够提供有用的解决方案和深刻的理解。在第二阶段，简单的滑动案例演变为连续体分析。实质点方法（MPM）提供了接近任意几何形状的可能性，并消除了简单情况的主要局限性假设，即故障机制及其后续传播的“先验”知识。有两个有据可查的脆性，高塑性渐进破坏案例，超固结粘土（Aznalcóllar和Selborne）提供了有用的数据来检查MPM分析的功能，以正确预测剪切面的内部发展和观测到的跳动。该方法还提供有关从基本“静态”行为到加速位移的过渡的信息。受Selborne案例启发，进行了敏感性分析，结果表明跳动与土壤脆性之间存在有趣的关系。速率对摩擦角的影响解释了滑坡的蠕变行为。在孔隙水压力的时间历程下，Vallcebre滑动速度的变化为简单的建模方法提供了验证方法。但是，摩擦定律不能轻易解释在Vajont等滑坡中观察到的突然加速。先前的解释在某些滑坡中观察到的快速加速和快速运动的工作依赖于热引起的滑动面的孔隙增压。为Vajont滑坡引入双楔的进一步工作强调了剪切带厚度，特别是土壤渗透性的相关性。通过MPM对所涉及的热-水力机械（THM）公式进行了概括，解决了解决由剪切带厚度的网格大小控制引起的不一致结果的难题。解决的办法是在描述土壤基质的材料点上嵌入合理厚度的剪切带。这种方法成功地复制了已知的Vajont故障后运动。该模型可以估算滑动岩体的内部剪切力，滑动表面的温度升高及其瞬时过大的孔隙压力。最后一部分描述了滑坡的蠕动运动与其最终向快速现象演变之间的密切关系。一个简单的平面幻灯片提供了一组控制交互作用的无量纲参数。应变速率对摩擦的影响解释了该问题的蠕变部分。本文通过MPM公式描述了一种通用方法来处理任意几何形状。Canelles滑坡有助于根据配方是否存在蠕变和THM物理及其可能组合来讨论预测的优缺点。最后一部分描述了滑坡的蠕动运动与最终演变为快速现象之间的密切关系。一个简单的平面幻灯片提供了一组控制交互作用的无量纲参数。应变速率对摩擦的影响解释了该问题的蠕变部分。本文通过MPM公式描述了一种通用方法来处理任意几何形状。Canelles滑坡对于根据配方是否存在蠕变和THM物理及其可能组合来讨论预测的优缺点很有用。最后一部分描述了滑坡的蠕动运动与最终演变为快速现象之间的密切关系。一个简单的平面幻灯片提供了一组控制交互作用的无量纲参数。应变速率对摩擦的影响解释了该问题的蠕变部分。本文通过MPM公式描述了一种通用方法来处理任意几何形状。Canelles滑坡对于根据配方是否存在蠕变和THM物理及其可能组合来讨论预测的优缺点很有用。本文通过MPM公式描述了一种通用方法来处理任意几何形状。Canelles滑坡对于根据配方是否存在蠕变和THM物理及其可能组合来讨论预测的优缺点很有用。本文通过MPM公式描述了一种通用方法来处理任意几何形状。Canelles滑坡对于根据配方是否存在蠕变和THM物理及其可能组合来讨论预测的优缺点很有用。