不同初始含水量条件下的堰塞坝溃决机理

在影响堰塞坝溃决的众多因素中，初始含水量影响堰塞坝的溃决机理仍不清楚。通过开展不同初始含水量条件下的水槽试验，详细探究了初始含水量对溃决过程的影响规律。结果表明：不同初始含水量条件下的溃决过程均具有3个典型阶段，分别是牵引侵蚀过程、溯源侵蚀过程和水沙运动再平衡过程；峰值流量随初始含水量的增大而增大，而溃决历时和残留坝体高度随初始含水量的增大而减小；随初始含水量的增大，溯源侵蚀作用逐渐减弱，牵引侵蚀作用增强；随初始含水量的增大，溃口展宽率降低，侵蚀率增大；初始含水量小于7.8%时，平均侵蚀率增长缓慢，大于7.8%后，平均侵蚀率增长迅速，且10.3%初始含水量对应的平均侵蚀率约为7.8%初始含水量的2倍；溃口宽深比在溃决的前两阶段随初始含水量的增大而减小；溃决结束后的宽深比随含水量的增大呈先趋近于1.00、后远离1.00的演变。

Influence of Initial Soil Moisture on Breaching Mechanism of Natural Dam

The breaching process of natural dams is influenced by many factors. However, it is still unclear about the effects of initial soil moisture on the discharge hydrograph and breach evolution. In this study, we conducted several laboratory tests to study how the initial soil moisture influences the breaching process of natural dams. The results show that there were three periods with different breaching characteristics in the breaching process with different initial soil moistures, namely the tractive erosion, the backward erosion, and the water and sand movement rebalance. The peak discharge increased with the increase of initial soil moisture. However, the breaching duration and dam height after dam failure decreased with the increase of initial soil moisture. The intensity of backward erosion decreased with the increase of initial soil moisture;in contrast, the tractive erosion enhanced with the increase of initial soil moisture. The greater the initial soil moisture was, the larger the incision rate was, and the incision rate increased slowly when the initial soil moisture was less than 7.8%, otherwise the incision rate increased quickly. In addition, the average incision rate at an initial water content of 10.3% was twice that of the initial water content of 7.8%. The ratio of breach width to depth decreased as the initial soil moisture increased before the last period. The ratio of breach width to depth after dam failure decreased with the increasing of initial soil moisture, which tended to be 1.00 and then less than 1.00 with increasing of the initial soil moisture.