土石坝漫顶溃决模式与溃坝参数预测

利用黏土和黄砂混合配制试验筑坝材料,开展水槽试验,模拟均质土石坝漫顶破坏过程,研究溃坝模式对溃坝参数的影响。试验中观测到3种漫顶破坏模式:陡坎蚀退冲刷溃决模式(M1)、剪切蚀退坍塌溃决模式(M2)和浸泡剥蚀破坏模式(M3)。相同库容和坝高条件下,不同模式最大溃决流量差异较大:Q_p(M2)>Q_p(M1,M3);定义水流开始漫顶至水库内库存水流构成漫坝破坏的主要动力源的时间为漫顶临界时间T_C,则T_C(M2)<T_C(M1)<T_C(M3)。溃坝模式反映了漫顶流量、初始溃口、坝高和筑坝材料等因素对漫顶溃决的综合影响,是除坝高、库容外溃坝参数预测的重要影响因子。

Impact of Overtopping Breach Mode on Dam-break Parameters of Homogeneous Earth-rock Dams

In order to simulate overtopping breach of homogeneous earth-rock dams, we carried out experiment in water tank using sand and clay to make mixed materials for dam, and discussed the impact of overtopping breach mode on dam-break parameters. We divided the overtopping breach modes into three kinds: erosion and scour of scarp(M1), erosion and collapse of shear (M2) and erosion and collapse of soak (M3). In the presence of given capacity of reservoir and dam height, maximum breach discharges (Q_p) of different modes are obviously unequal, and Q_p of M2 is the biggest. Breach Critical time(T_C) is referred to as the time from the beginning of overtopping to the developing of breach, and T_C of M2 is the smallest, followed by that of M1 and M3. Breach mode depicts the effects of overtopping flow, initial breach, dam height and dam materials on dam-break process. Besides dam height and capacity of reservoir, breach mode is another important factor for dam-break prediction and disaster assessment.