Experimental Study On Water Flow Characteristics And Water Failure Process Of Groin Dam Under Bend Condition

Groin dam has been one of the most widely used structures in waterway regulation because of its remarkable river control advantages.The root of the groin connected with the bank slope plays an important role in ensuring the safety of the groin structure and the stability of the dam body,and is also one of the important parts to play the function of the groin bundle water attacking sand and stabilizing the navigation channel.Under the influence of inflow conditions,erosion and water damage in this part often occur,and the water damage at the dam root will reduce the overall improvement effect of the groin,and then may affect the navigation safety.Therefore,the stability of the dam root area should be considered in the engineering design,and necessary prevention and control measures should be taken.In this paper,FLOE-3D software is used to study the flow distribution characteristics of submerged groin at the root of the dam under different influencing factors such as flow,dam length and location,and physical moving bed test is used to analyze the water failure process of the dam root under the above-mentioned influencing factors.The main conclusions are as follows:（1）Based on the mathematical model test,it is concluded that the velocity at the root of the dam is positively correlated with the flow rate and dam length under a certain outlet water level,and is slightly different from the position of the groin.The impact of surface water is easy to affect the stability of dam root and bank slope,and the impact of trough bottom water is weak and small.（2）When the flow rate increases,the velocity in the bend speeds up accordingly.Under the action of centrifugal force and inertial force,the longitudinal water level shows opposite changes on the convex bank of the bend;With the increase of groin length,the water level difference between upstream and downstream of dam root increases.As the groin moves from upstream to downstream,the range of backwater in the upper reaches of the dam root increases gradually.（3）Based on the physical model test,it is concluded that the sand washed away at the dam root is often carried by the current to the back slope of the dam body and deposited,and the sand ridge accumulation of a certain height is formed.The water damage of the dam root is mainly caused by the loss of sand and stone on the bank slope caused by the continuous erosion of water flow or the formation of scouring pit at the dam root end.（4）According to the measured data of the erosion pit at the root of groin dam and the analysis of the erosion process under various test conditions,the flow rate is the key factor to destroy the stability of the dam root.The area of the scour pit at the dam root can be roughly represented by an ellipse,and the plane area and volume of the scour pit can be estimated by the ellipse area and volume formula,which provides a reference for delineating the protection area of the dam root and the secondary reconstruction.Through multivariate nonlinear fitting,the theoretical formula of dam root water damage length is obtained:L/L₀=（Q/Q _O）^-0.1756（b/B）^0.5285（c/C_O）^-0.1786,the degree of dam root water damage can be estimated by this formula,and a more reasonable protection range of dam root can be selected.