Dynamic Simulation Analysis Of Hydraulic And Water Quality In The Conveyance Tunnel Of The Project Of

The project of water division from Han to Wei river is a giant inter-basin water transfer project.With the project,the water consumption of several major cities along Weihe is supplemented,which alleviated the problem of water shortage in the city and realized the optimal allocation of water resources.The Qinling water conveyance tunnel is regarded as the key projcct to connect the water source area and the water intake area.There is no project other than the Huangjinxia reservoir,Sanhekou pumping stations,and control gates for regulation.Once the water flows through the control gate and reaches the Yueling section,artificial regulation will not be possible.Therefore,studying the hydraulic characteristics and water quality of tunnels in the Yueling section not only ensures the safety of the tunnel itself and water supply,but also provides scientific decision-making basis for improving the time efficiency of water supply，controlling the risk cost of water quality problems,and ensuring the economic benefits of the project,which has significant theoretical significance and applicable value.The Qinling water conveyance tunnel is taking as the research object in this paper.Based on the tunnel design datas,the hydraulic characteristics and basic water quality were studied by subsection summation,MIKE11 HD,a simple hydraulic method,MIKE11 AD,ECO Lab and so on.The main research achievements of this paper are as follows:(1)Aiming at the complex cross-sectional shape of the Qinling water conveyance tunnel,a simplified treatment is carried out.According to the hydraulic formula,calculate the normal water depth,critical water depth,and critical bottom slope under the design discharge.The water flow state is judged as slow flow by the method of water depth,and the bottom slope is gentle.(2)The MIKE11 HD model is established to simulate the flow pattern of the tunnel,water surface profile and the changes in water depth at key section.Compared with the surface line calculated by the subsection summation method,the surface profile of the two methods are consistent,and the water level error of the same section can be ignored.The results show that the surface line is basically parallel to the bottom of the tunnel.As the flow increases,the surface profile rises up,the flow decreases,and the water surface line drops.With the same flow,the greater the roughness coefficient of the tunnel,the higher the surface line,the smaller the roughness coefficient is,and the lower the surface line.(3)The maximum roughness coefficient under design flow is 0.0161,and the maximum flow under design roughness is 76m3/s,which satisfying the tunnel pressureless condition.(4)The MIKE11 AD model is established to simulate the flow of the conservative substance A in the water flow,and the evolution time of different flows was obtained.Compared with the flow evolution time calculated by the simple hydraulic method,the relative error under various operating conditions remained at 0.3-2.6%(Table 4-7).When the flow rate is 70m3/s,the simple hydraulics flow evolution time is 9.77h,and the MIKE11 AD model simulation time is 10.00h.The results show that MIKE11 AD model is easy to calculate,intuitive and reliable.At the same time,the greater the flow,the shorter the duration of evolution,and the constant the flow,the greater the coefficient of roughness and the longer the duration of evolution when the roughness is constant.(5)A MIKE11 AD and ECO Lab coupling model is established to simulate DO,BOD,and ammonia nitrogen concentrations with two point source locations.The results show that when there is no DO in the point source pollution,the peak concentration of the outlet section decreases with the increase of the tunnel water flow.When other conditions are identical,the location of point source is closer to downstream outlet,and the peak value of material concentration at outlet section is bigger,and the peak time is earlier.Regardless of the point source location,with the increase of flow in the tunnel,the peaks of BOD and NH3-N concentration at the outlet section decreased,and the peak present time advances.When the flow rate of the tunnel is constant,the greater the point source flow,the higher the BOD and ammonia nitrogen concentration at the outlet section.With the increase of water flow in the tunnel,the peaks of BOD and ammonia nitrogen concentration at the outlet section decreased,and the peak time decreased.