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岩心，进入防洪堤水坝的过滤器时，就会发生岩心过顶。它可以导致芯和过滤器之间的界面内部侵蚀，并最终损坏。通过保持上游储层的低水位，可以避免岩心过顶。然而，低水库水位会给大坝所有者带来经济后果。对于复杂坝型、瞬态流动和广泛分级的岩心材料，岩心过顶过程中接触侵蚀过程的实验数据很少。因此，对大坝业主来说，更好地了解堆芯溢顶的实际影响是很重要的。该项目的主要目标是收集实际几何形状、材料和流动条件下的堆芯超顶实验数据，并为这一现象建立数值模型。在项目的第一阶段，岩心过顶将用不同岩心和过滤器粒度分布的实验室模型进行实验复制。被测试材料的选择将使某些组合不符合抗侵蚀稳定性的公认设计标准。将对具有广泛分级核心的加拿大堤防水坝的代表性组合进行测试。在项目的第二阶段，将编写一个数值模型来复制实验结果。在实践中广泛使用的连续体模型在模拟依赖于微观尺度行为的现象时表现不佳，例如内部侵蚀。数值模型将基于一种新颖的多尺度方法。它将结合颗粒尺度建模与离散单元方法，其中单个颗粒的位移建模（软件YADE），以及大尺度建模与有限元方法，其中土壤作为一个连续体建模（软件COMSOL）。目前加拿大有1万多座水坝。一个实用的多尺度模型和实际几何形状和材料的侵蚀阈值和侵蚀速率的实验数据将允许在岩心过顶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.