Dam and embankment breaching from overtopping is important to both engineers and planners. The processes observed during overtopping and breach tests conducted on large-scale models as well as preliminary analysis of the results are described in this paper. Three large-scale embankments, two at 2.3 m and one at 1.5m in height have been tested. Two of the embankments, 2.3 m high and 1.5 m high, had three test sections, 7.3 m and 4.9 m wide with 2 m and 1.5 m trapezoidal notch overflow sections respectively, and 3H:1V slopes on both the upstream and downstream sides, consisting of three materials varying from a non-plastic SM silty sand to a CL lean clay. The other embankment, 2.3 m high, had a single 12 m wide test section of non-plastic SM silty sand with an 8.2 m wide trapezoidal overflow notch. The erosion process during overtopping and breaching was observed to be multi-phase: initial downstream surface erosion progressing into stair-stepped multiple overfalls, ultimately merging into a single upstream-migrating headcut. The rate of upstream headcut migration from these tests is evaluated based on measured material properties, hydraulic parameters during overtopping, and physically based analytic procedures. Headcut migration rates ranged from 0.15 to 0.003 m/min for the 2.3-m high embankment and 0.15 to 0.001 m/min for the 1.5-m high embankment depending on material type. Measured soil properties help explain for the difference in migration rates of the headcuts. The rate of headcut migration is an important part of the rate of breach development. Prediction of headcut advance rate for varying conditions will play a key role in evaluating the timing and magnitude of the outflow hydrograph from an overtopping failure event.
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机译：大坝和路堤因过顶而遭到破坏对工程师和规划者而言都是重要的。本文描述了在大规模模型上进行的覆盖测试和突破测试期间观察到的过程以及对结果的初步分析。测试了三个大型路堤，其中两个高度为2.3 m，一个高度为1.5m。其中两个路堤分别为2.3 m高和1.5 m高，具有三个测试段，分别为7.3 m和4.9 m宽，梯形缺口溢流段分别为2 m和1.5 m，并且上游和下游侧的坡度均为3H：1V，包括三种材料，从非塑料SM粉砂到CL贫粘土。另一条路堤高2.3 m，有一个非塑料SM粉质砂的单个试验段宽12 m，具有8.2 m宽的梯形溢流口。观测到的覆盖和破坏过程中的侵蚀过程是多阶段的：最初的下游表面侵蚀逐渐发展为阶梯状的多次塌陷，最终合并为一个上游迁移的顶部。根据测得的材料特性，覆盖过程中的水力参数以及基于物理的分析程序，评估这些测试中上游割草迁移的速率。根据材料类型的不同，2.3 m高的路堤的割据迁移速率范围为0.15至0.003 m / min，1.5 m高的路堤的割据迁移速率范围为0.15至0.001 m / min。测得的土壤性质有助于解释割口迁移率的差异。快捷迁移的速度是违规发展速度的重要组成部分。预测各种条件下的顶切推进速率将在评估因超车失败事件而引起的流出水文图的时间和大小方面发挥关键作用。
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