Study On The Laws Of Sediment In The Chaihe Reservoir

Sediment deposition is one of the key problems that restrict the long-term use of reservoirs.It not only directly affects the normal operation of reservoirs and the functions of flood control and irrigation,but also brings inconvenience to people's lives due to water pollution caused by reservoir sedimentation.It has been uninterrupted on reservoir sedimentation,such as sedimentation,sediment distribution,estimation of sediment and sediment motion,but there is less research on the Northeast river type reservoir.Taking Chaihe Reservoir as an example,mainly through the test of river sediment sediment sampling,the physical characteristics of sediment was analyzed,combined with mathematical model,the reservoir silting state and distribution law are studied,and the capacity curve is checked,so as to provide the theory basis for the reasonable operation of Chaihe Reservoir and management providing reference for the Northeast river type reservoir with practical significance.Reservoir sedimentation is related to sediment gravity characteristics,geometric characteristics,sediment motion and other factors,therefore,this paper uses acoustic drilling rig to carry out field sampling for typical section of reservoir area.The soil samples and sediment settling tests of the deposited silt samples were carried out.The dry bulk density,particle gradation and settling velocity of sediment were analyzed respectively.By using Mike21 software and the included hydrodynamic module and sediment transport module,two dimensional mathematical models of water and sediment are established,the river bed height change and deposition distribution in the long series operation of reservoir area were simulated and analyzed,and the deposition form and volume change of sections were analyzed with Surfer software,the main conclusions are as follows:(1)The dry density of sediment in surface and coarse sand content decrease along the flow direction,and the dry density and sediment grain size increases with the increasing deposition thickness,while dry density increases with increasing particle size.(2)With the increase of the operation time of reservoir,presenting different degrees of deposition in reservoir,while the river ratio decreases.Deposition is mainly concentrated near the bend and extends downstream,until the silting is near the front of the dam(9#section),where the maximum thickness is1.27m.(3)From the sediment formation,the longitudinal deposition of reservoir lies between the zonal deposition and the delta deposition,and there is more deposition in bend and beach land.Deposition state of cross section:There is main channel deposition in the broad river and the remaining positions are evenly silted along the wet cycle.(4)The storage capacity of the reservoir decreases with the increase of time.At the same time,the amount of sand entering the reservoir also decreased,and the deposition rate slowed down.The corresponding reservoir capacity of design flood level is 4.62×10~8m~3,which is 0.18×10~8m~3 less than that in the initial stage.And the deposition in reservoir area for the next decade is predicted.