入流泥沙粒径组成对弱分层水体异重流及挟沙特性的影响

利用水槽设计水库分层水体模型试验,研究温度弱分层水体中不同入流泥沙粒径组成时异重流及其泥沙运动的特性。选用颗粒粒径0.01 mm、0.02 mm、0.05 mm的泥沙,开展了不同入流泥沙粒径组成条件下的异重流试验研究。在水温弱分层水库水体中,分析入流泥沙粒径组成的变化对分离点水深和间层流厚度的影响规律;不同泥沙粒径组成下,分析异重流在水库断面的泥沙浓度、较深的水域挟沙量变化规律;研究了泥沙沉淀量和悬浮量与入流泥沙粒径组成的关系。研究结果表明:在弱分层条件下,维持入流泥沙浓度3.75 g/L、入流速度0.005 m/s不变,异重流在水库中泥沙沉淀比例为29%~38%,泥沙在水库中的悬浮比例为46%~60%;粒径组成变化导致分离点深度和间层流厚度不同,颗粒粒径越大,分离点深度越深,间层流厚度越厚;异重流挟沙能力弱,水库淤积更严重,泥沙也会造成水库水浑浊;入库泥沙粒径越小,水库悬浮的泥沙浓度越大,水库的内源污染越大;当入库泥沙粒径较小时,宜在水库深水区取水,可减少水处理费用。研究成果可为水库取水、调水调沙提供参考。

Impact from composition of particle size of inflowed sediment on density flow and its sediment laden characteristics of weakly stratified water body

The density flow and its sediment movement characteristics of various compositions of particle size of the inflowed sediment in weakly stratified water body are studied through designing a flume model experiment for the stratified water body in reservoir. For which， the sediments with the particle sizes of 0.01 mm， 0.02 mm， 0.05 mm are selected for carrying out the experimental study on the density flow under the conditions of various compositions of particle size of inflowed sediment. In the weakly temperature-stratified water body of reservoir， the law of the impact from the change of the composition of the particle size of the inflowed sediment on the water depth at the separating point and the thickness of the interflow is analyzed， while the laws of changes of the sediment concentration of the reservoir profile and the sediment laden amount at the deeper water area of the density flow are analyzed， and then the relationship between the deposition and suspension of sediment and the composition of the particle size of the inflowed sediment is studied as well. The study result shows that under the weakly stratified condition， the proportion of the sediment deposition of the density flow in reservoir is to be 29%~38% and the proportion of the sediment suspension of the density flow in reservoir is to be 46%～60%， if the concentration of 3.75 g/L and the inflow velocity of 0.005 m/s of the inflowed sediment maintain constant， while the change of the composition of the particle size leads to the difference between both the water depth at the separating point and the thickness of the interflow， i.e. the larger the particle size is， the deeper the depth at the separating point is to be； the deeper the depth at the separating point is， the thicker the interflow is to be； the weak the sediment laden capacity of the density flow is， the more serious the reservoir sedimentation is to be， and the sediment can also make the water in reservoir turbid； the small the particle size of the inflowed sediment is， the larger the concentration of the suspended sediment in reservoir is to be and the larger the endogenous pollution ofreservoir is be as well. When the particle size of the inflowed sediment is smaller， it is favorable to take water from the deep water area of reservoir， thus the water treatment cost can be reduced. The study result can provide a reference for reservoir water taking and water and sediment regulation.