Study On The Development Law Of Longitudinal Crack And Dam Failure Mechanism Of Embankment Dam Under Flood Overtopping

Reservoir dams are crucial components of water conservancy infrastructure and flood control engineering system,playing an important role in optimizing the allocation of water resources,preventing floods and drought,and improving river navigation conditions.Dam break issue usually cause catastrophic damage.Embankment dams has the longest history and the most extensive application in the field of dam construction.Restricted by the economic and technological conditions during the construction period,many embankment dams were built with low quality and construction level,which caused significant potential safety hazards and seriously threaten the economic and social development and ecological environment of downstream areas.Longitudinal cracks are one of the most common earthquake damage phenomena of embankment dams.However,few studies focus on the longitudinal cracks of embankment dams.The effect of longitudinal cracks on embankment dams failure process caused by overtopping is not clear.It is helpful to develop and improve the theory of embankment dams failure by studying the secondary disasters of longitudinal cracks and the mechanism of dam failure under extreme flood overtopping conditions,which is significance to the risk assessment of embankment dam failure and the flood warning and emergency plan formulation of dam failure.Outdoor physical model experiments of longitudinal crack development and embankment dams failure were carried out under flood overtopping conditions.The laws of longitudinal crack development and dam break process under overtopping conditions were studied.The chain dam failure process of downstream embankment dams resulted in upstream dam-break flood was explored.The law of dam-break flood evolution was analyzed,and the prediction models of embankment dam breaching parameters were established.The main research work and achievements in the present thesis could be summarized as follows:(1)Outdoor physical model experiments corresponding to flood overtopping were carried out and embankment dam overtopping failure process was studied.According to the experimental observation,the overtopping failure process of typical embankment dam model(without presupposed longitudinal cracks but presupposed initial breach)is divided into four stages.In addition,the chain dam break process of downstream embankment dams were explored.The results show that embankment dams in downstream area were overtopped directly by upstream dam break floods.Compared with typical embankment dam overtopping failure process,the failure process of embankment dams in downstream area is different and the failure duration is significantly reduced.(2)According to the experimental observation,the effects of preset longitudinal crack,longitudinal crack size and initial breach on embankment dam overtopping failure process are compared.The results show that increasing the size of longitudinal crack and setting initial breach could accelerate the failure process of embankment dam when other test conditions are constant.(3)Prediction models relating to peak discharge and mean breach width resulted in two different modes of overtopping and piping were developed.The evaluation results of the goodness of fit,degree of significance and formula verification show that the prediction models have good prediction accuracy and the ability to quickly and effectively predict peak discharge and mean breach width,which will provide important references for risk prediction and evaluation of embankment dams.Figure [27] Table [13] Reference [84].