A hierarchical multiscale modeling framework is proposed to simulate flowslide triggering and runout. It couples a system-scale sliding-consolidation model (SCM) resolving hydro-mechanical feedbacks within a flowslide with a local-scale solver based on the discrete element method (DEM) replicating the sand deformation response in the liquefied regime. This coupling allows for the simulation of a seamless transition from solid- to fluid-like behavior following liquefaction, which is controlled by the grain-scale dynamics. To investigate the role of grain-scale interactions, the DEM simulations replace the constitutive model within the SCM framework, enabling the capture of the emergent rate-dependent behavior of the sand during the inertial regime of motion. For this purpose, a novel algorithm is proposed to ensure the accurate passage of the strain rate from the global analysis to the local DEM solver under both quasi-static (pre-triggering) and dynamic (post-triggering) regimes of motion. Our findings demonstrate that the specifics of the coupling algorithm do not bear significant consequences to the triggering analysis, in that the grain-scale dynamics is negligible. By contrast, major differences between the results obtained with traditional algorithms and the proposed algorithm are found for the post-triggering stage. Specifically, the existing algorithms suffer from loss of convergence and require proper numerical treatment to capture the micro-inertial effects arising from the post-liquefaction particle agitation responsible for viscous-like effects that spontaneously regulate the flowslide velocity. These findings emphasize the important role of rate-dependent feedback for the analysis of natural hazards involving granular materials, especially for post-failure propagation analysis.

中文翻译：

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流动滑动触发和跳动的颗粒动力学的多尺度建模

提出了分层多尺度建模框架来模拟流动滑动触发和跳动。它将解决流动滑坡内的流体力学反馈的系统规模滑动固结模型 (SCM) 与基于离散元法 (DEM) 的局部规模求解器相结合，复制液化状态下的砂体变形响应。这种耦合允许模拟液化后从固体到类流体行为的无缝过渡，这是由颗粒尺度动力学控制的。为了研究颗粒尺度相互作用的作用，DEM 模拟取代了 SCM 框架内的本构模型，从而能够捕获沙子在惯性运动状态下出现的速率相关行为。为此，提出了一种新颖的算法，以确保在准静态（预触发）和动态（后触发）运动状态下，应变率从全局分析准确传递到局部 DEM 求解器。我们的研究结果表明，耦合算法的细节不会对触发分析产生重大影响，因为颗粒级动力学可以忽略不计。相比之下，传统算法和所提出的算法在后触发阶段获得的结果之间存在主要差异。具体来说，现有算法存在收敛损失，并且需要适当的数值处理来捕获液化后粒子搅拌产生的微惯性效应，该效应负责自发调节流动速度的粘性效应。这些发现强调了速率相关反馈对于涉及颗粒材料的自然灾害分析的重要作用，特别是对于故障后传播分析。