Experimental Study On Water Diversion And Sand Control By Different Water Intake Schemes In A Diversion Project

With the economic development and the huge development of water conservancy and hydropower technology,the demand for water resources in various regions is increasing.In order to meet the needs of irrigation,power generation and urban drinking water in different regions,China has built many small water conservancy hubs,especially headworks.This project is a water diversion hub in the southwest of Xinjiang.The river flow in this project is subject to seasonal influences and has the characteristics of large sediment content,long dry period and concentrated flood period.The construction of a diversion hub on such a river is bound to deal with the sediment problem.The key issue of whether the diversion hub can guarantee long-term and efficient water use is whether the sediment problem in the river is properly handled.Therefore,it is for this practical project to establish the physical model of river engineering,combined with the model test to explore the river flow characteristics of two new layout schemes of diversion sluice,and give the optimal scheme.And then the muddy water movable-bed test is carried out and analyzed the influence of different water and sediment conditions on the headwork.The experimental results provide scientific and reliable foundations for the actual project and give reasonable suggestions to avoid the adverse situation;The concrete results are as following:(1)It can be seen from the clear water test that both of the two design schemes can meet the requirements water diversion capacity,but the single-hole scheme has the advantages of good flow state in front of the inlet,uniform flow velocity and few low flow velocity zones.From the overall layout of the river,the single-gate scheme has a stronger discharge capacity than the double-hole scheme,and a higher average velocity of the river,which is helpful to reduce the desilting and improve the effect of sluice sluicing and desilting.Therefore,it is recommended to adopt the design scheme of single-hole water diversion gate,and based on which the muddy water movable-bed test was carried out.(2)For the design condition of 120 days of dry water period,the sedimentation thickness of the river in front of the sluice gate tends to increase at first and then slowly.According to the growth trend of the sedimentation thickness,it is expected that the final sedimentation thickness will reach 97 centimeters.On the whole,the deposition shape of the river course is a gentle belt,and the cross section of the riverbed is relatively flat.The deposition gradually thickens from the front of the sluice gate to the upstream,and a large number of silting are formed at the entrance of the diversion dike.As the most unfavorable condition,the discharge and drainage tests were carried out on the riverbed,and the drainage effect was not very good,which greatly damaged the benefits of reservoir.(3)As for normal diversion flow condition,the vertical sediment concentration and sediment transport rate of the two sections in front of the gate,verified the effect of hanged plate and the feasibility of its setting height.Cumulative sedimentation tests were also carried out,sediment in rivers continues to increase over time,at the relative water depth of y/h=0.5,the sand content around the river and the gate has been increasing,the sediment will reach the hanged plate after 70 days,and the average sand content increased by 80 percent,so it was urgent to open the sluice and flush the sand.(4)A common mixed flood sand experiment was carried out based on the former bed,the measured outgoing sediment content decreases sharply,but it is always higher than the incoming sediment content,the comprehensive desilting efficiency is about 103.7.At the same time water diversion test also conducted during the flood season,it is concluded that the higher the gate opening,the higher the sediment content of the diversion water.According to the theory of critical sediment carrying capacity,it couldn't cause the diversion channel siltation during flood season.(5)The problem of suspended sediment deposition in the river channel in front of the gate is analyzed with the measured data,and tested the applicability of the typical sedimentcarrying force formula in the river channel of this project.Finally,the formula is obtained by adjusted and fitted the sand-carrying force formula of wuhan university.Based on this,the estimation method of sediment volume and sediment thickness before sluice gate is given.