Development and experimental validation of a multiscale DEM-FEM model for core overtopping in embankment dams

当水位超过不透水的核心，进入区域堤坝的滤层时，就会发生溢心现象。它可能会导致滤芯和过滤器界面处的内部侵蚀，最终导致堤坝失效。通过保持上游水库的低水位，可以避免岩心溢流。然而，低水库水位可能会给大坝所有者带来经济后果。对于复杂的坝体几何形状、瞬变流和广泛分级的心墙材料，关于心墙越坝过程中接触侵蚀发展的实验数据很少。因此，对大坝所有者来说，更好地了解核心溢流的真正影响是很重要的。该项目的主要目标是收集真实几何形状、材料和流动条件下的岩心溢流实验数据，并为这一现象开发一个数值模型。在该项目的第一阶段，将利用实验室模型对不同的岩芯和过滤器粒度分布进行岩芯溢流的实验复制。测试材料的选择将使某些组合不符合公认的抗侵蚀稳定性设计标准。具有广泛分级心墙的代表加拿大土石坝的组合将进行测试。在该项目的第二阶段，将编制一个数值模型来复制实验结果。在实际中广泛使用的连续介质模型在模拟依赖于微尺度行为的现象时表现不佳，例如内部侵蚀。数值模式将基于一种新的多尺度方法。它将结合颗粒尺度模拟和离散元方法，其中单个颗粒的位移被模拟(YADE软件)，以及大尺度模拟和有限元方法，其中土壤被模拟为一个连续体(软件COMSOL)。加拿大目前有10,000多座大坝。对于真实的几何和材料，一个实用的多尺度模型和关于侵蚀阈值和侵蚀速率的实验数据将允许在岩心溢出的情况下采取适当的行动。它还将有助于设计新的结构。

Core overtopping occurs when the water level rises over the impermeable core, into the filter of zonedembankment dams. It can lead to internal erosion at the interface between core and filter, and eventually to damfailure. Core overtopping can be avoided by maintaining a low water level in the upstream reservoir. However,low reservoir levels can have economic consequences for dam owners. Experimental data on the progression ofcontact erosion during core overtopping for complex dam geometries, transient flow and widely graded corematerials are scarce. As a consequence, it is important for dam owners to get a better understanding of the realimpact of core overtopping. The main objectives of this project are to gather experimental data on coreovertopping for realistic geometries, materials and flow conditions, and to develop a numerical model for thisphenomenon. In the first phase of the project, core overtopping will be replicated experimentally with alaboratory model for different core and filter grain size distributions. The tested materials will be chosen so thatsome combinations fail to respect the accepted design criteria for stability against erosion. Combinationsrepresentative of Canadian embankment dams with a widely graded core will be tested. In the second phase ofthe project, a numerical model will be programmed to replicate the experimental results. The continuummodels that are widely used in practice perform poorly when modelling phenomena that are dependent onmicroscale behaviour, such as internal erosion. The numerical model will be based on a novel multiscaleapproach. It will combine particle scale modelling with the discrete element method, where the displacement ofindividual particles is modelled (software YADE), and large scale modelling with the finite element method,where the soil is modelled as a continuum (software COMSOL). There are currently more than 10,000 dams inCanada. A practical multiscale model and experimental data on erosion threshold and rate of erosion forrealistic geometries and materials will allow appropriate actions to be taken in case of core overtopping. It willalso help design new structures.