Earth Dam Breaking: the Process and Mechanism

摘要

Breach formation and development in earth dams is a complicated process depending on many factors and varies greatly from case to case. Despite the numerous studies conduc-ted, the knowledge of the breach erosion mechanism in earth clams is still rather poor. In the present study, based on observation of prototype earth dam breaking and experiments in the laboratory and in the field, the process and mechanism of earth dam breaking due to over-flowing has been investigated and described. The whole breach erosion process in earth clams can be generally distinguished into four stages. During the first stage, the overtopping flow lowers the dam crest and steepens the downstream slope of the clam until a certain critical an-gle is arrived. Then in Stages Ⅱand Ⅲ, flow shear erosion, dam foundation scour and head-cut mass wasting occur and weaken the dam body until the dam is completely broken through at the end of Stage Ⅲ. For the last stage (i. e. Stage Ⅳ), breach erosion takes place mainly laterally.