Dam breach analyses for tailings dams currently rely heavily on relationships and methods derived for water retaining dams, despite significant differences in design, construction, dam materials, and geometry; particularly, the upstream face of the dam. Conventional tailings slurry deposition from the dam crest typically forms low angle upstream beaches (1–2 % inclination) within the impoundment. In this paper, we isolate the effect of tailings dam beach geometry at the time of overtopping on breach characteristics using physical and numerical modeling. Five 1 m high homogeneous fine sand dams with beach heights of 0.5 to 0.9 m and a beach slope of 5 % were brought to failure by v-notch overtopping. The laboratory data revealed that a threshold beach height existed above which the peak discharge was progressively limited by the geometry of the reservoir. Numerical simulations, performed in XBeach, captured this effect in the outflow hydrographs, with differences between physical and numerical model peak outflow generally within 25 %. Another key model parameter in tailings dam breach analysis is the volume of tailings solids lost through erosion during breach. Comparison of terrestrial laser scanning elevation profiles, cut through the centreline of the physical model, with XBeach simulations indicate XBeach can replicate the bulk characteristics of erosion when a tailings-style beach is present. These findings show that hazard analysis for overtopping failure in tailings dams should consider the effect of tailings dam beach geometry on the outflow hydrograph, and forms a growing case of evidence to support the use of XBeach for simulation of dam breach.

中文翻译：

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尾矿坝滩对溢流破坏期间决口流出和侵蚀的影响


尾矿坝的溃坝分析目前在很大程度上依赖于蓄水坝的关系和方法，尽管在设计、施工、坝体材料和几何形状方面存在重大差异;特别是大坝的上游面。来自坝顶的常规尾矿泥浆沉积通常在蓄水池内形成低角度上游海滩（1-2% 的倾斜度）。在本文中，我们使用物理和数值建模分离了溢流时尾矿坝滩几何形状对决口特征的影响。五座 1 m 高的均质细沙坝，海滩高度为 0.5 至 0.9 m，海滩坡度为 5%，因 V 型缺口覆盖而失效。实验室数据显示，存在一个阈值海滩高度，超过该阈值，峰值流量会逐渐受到储层几何形状的限制。在 XBeach 中执行的数值模拟在流出过程图中捕获了这种影响，物理和数值模型峰值流出之间的差异通常在 25% 以内。尾矿坝决口分析中的另一个关键模型参数是决堤期间因侵蚀而损失的尾矿固体量。穿过物理模型中心线的地面激光扫描高程剖面与 XBeach 模拟的比较表明，当存在尾矿式海滩时，XBeach 可以复制侵蚀的体量特征。这些发现表明，尾矿坝溢流破坏的危害分析应考虑尾矿坝海滩几何形状对流出过程线的影响，并形成越来越多的证据来支持使用 XBeach 模拟溃坝。