Analysis On The Flow Characteristics Of Stepped Warping Over Dam And The Preliminary Study On The Construction Of Ecological Bag

Warping dam has a long history in Loess Plateau,which plays a very important role in controlling soil erosion.Most of the warping dams are small dam,the flood in this area usually has high peak and small flow,short flow time and a few use times.It is urgent to develop a simple and safe flood discharge technology.Which can achieve the purpose of resources conservation and environmental protection,in this paper,based on the concept of the whole section of the dam surface and the dispersive energy dissipation,the solution of the dam drainage project constructed by the ecological is raised.Based on the RNG k-ε turbulence model and VOF free surface capture technology to improve the traditional stepped spillway design,and the main research contents and results are as follows:(1)This paper analyzed the geometric and hydrological characteristics of small and medium-sized warping DAMS in the loess plateau,and simulate the smooth flow of spillway of 50% dam crest.small energy dissipation rate leads to a large flow velocity at the bottom and a large scouring effect on the bottom.In order to study the full coverage of silting dam in northern Shanxi,the characteristic size and the range of characteristic flow of warping DAMS are determined,and the corresponding numerical calculation model is established and verified.(2)In order to enhance the energy dissipation rate of spillway,four types of spillway body types are designed,including pure stepped spillway,pre-aerated stepped spillway,platform stepped spillway and differential stepped spillway,the hydraulic characteristics and energy dissipation rate are simulated and the suitable range of different body types is obtained.(3)In this paper,different optimized body shapes are simulated,the results are applied to four warping dams in northern Shanxi and optimum shape for different warping dams is selected.The results show that the Niujiagou warping dam and the Qiandujiagou warping dam have the best performance and energy dissipation effect under the differential stepped spillway;The energy dissipation of Fengjiagou 2# warping dam is the best under the pure stepped spillway;the Majiagouzhenggou warping dam can achieve great dissipation effect in both pure stepped spillway and differential stepped spillway.The energy dissipation rate reached 80%.(4)According to the research on the shear stress of the step plane and the vertical plane,it is found that the theoretical analysis of the strength of the ecological bag can meet the structural stability requirements of the step spillway.Based on the distribution characteristics of the shear stress of the dam surface,the preliminary design adopts the vertical and then horizontal ecological bag structure,the ecological bags are connected by three-dimensional drainage coupling buckle,which makes them more suitable for spillway engineering.