Study On The Evolution Law Of Upstream Dam Breach Flood In The Downstream Reservoir Area And The Climbing Process Of Dam Surface Water Flow

In order to exploit and utilize water resources,a large number of reservoir dams have been built in China.The reservoir dam not only maximizes the comprehensive utilization of water resources,but also breeds potential risks.Along with the passage of time,many reservoirs inevitably appear the phenomenon of aging and dam disease.When the risk accumulates to a certain extent,or when extreme external loads,such as sudden earthquakes,violent floods,wars,etc.,reservoir dams may break.Dam break is the extreme risk consequence of reservoir dam.At present,the research on dam break is mainly about the evolution law of single dam break flood,but aiming at the flood evolution of dam break in upstream of cascade reservoir but not in downstream dam,There are few studies on the influence of backflow and the climbing process of flood in front of the dam.On the basis of previous studies,a series of dam-break tests have been carried out in rectangular cross-section flume to realize the rapid top-down breakout of the upstream water body by the way of rapidly pulling down the sluice gate.The main contents and conclusions are as follows:(1)The dam breaking tests with different downstream initial water depth conditions are carried out by using the cascade flume model.The results show that the initial water depth of the downstream reservoir has a great influence on the dam break flow movement model.According to the initial water depth in the downstream reservoir area,the evolution process of dam-break flood in the downstream reservoir can be roughly divided into three modes: climbing model,leaping model and advancing mode.(2)When the upstream reservoir dam breaks but the downstream reservoir dam does not break,the flood evolution process at the upstream dam(i.e.the gate)is obviously divided into four stages,that is,the stage of rapid decline of the water level and the stage of relative stability of the water level.The water level rises and the water level drops slowly.(3)The initial water level in the upper and lower reaches of the reservoir area,that is,the head difference of the upstream and downstream reservoir areas,has a great influence on the velocity of velocity in the process of dam break flood evolution and the height of flood climbing in front of the dam.The evolution and backflow velocity of upstream dam-break flood in the downstream reservoir area are significantly decreased after entering the reservoir area under the condition that there is water in the reservoir area.(4)Backflow occurs when dam-break flood reaches downstream dam surface,and jet flow occurs at the interface between negative wave generated by backflow and dam-break wave propagating downstream,and the size of jet is positively correlated with the depth of water in downstream reservoir area.The size of the jet is larger than that formed during the evolution of dam-break flood to the downstream.Figure [25] Table [6] Reference [81]...