Study On The Influence Of Flood Inflow Into Main Channel On Water Transport Capacity And Sediment Deposition

In the safe operation of the south-to-north water transfer project,the influence of external natural disasters such as floods is often considered.The construction of the south-to-north water transfer project to many water can't normal excretion from west to east,therefore the construction of inverted siphon conveyance structure for the flow,when flood water is abundant in sediment carrying excessive floods,floods caused by flood discharge capacity is insufficient siphon building overflow into the main canal,this kind of phenomenon will not only make the main canal water surge,Moreover,the sediment carried by the external flood into the main channel will cause siltation in a certain range of the channel,which will directly affect the channel flow capacity,and seriously affect the stability of the channel embankment.The study on the influence of the external flood carrying sediment flowing into the main channel of the south-to-north water transfer project is of certain guiding and reference significance to the stable operation and emergency treatment of the project.In this thesis,physical model test and theoretical analysis are combined,and based on previous research results,the influence of external flood sediment concentration on the water level of the main channel and the upstream water pulsation intensity of the inlet section is discussed by taking xixiaotun main channel of Xinghan Section of the middle route of the South-to-North Water Transfer project as the research object.On this basis,the relationship between different external flood sediment concentration and sedimentation form and sedimentation process is studied,and the conclusions are as follows:(1)The difference of external flood volume and sediment concentration has an effect on the water level of the main channel,and the flow volume is the main influencing factor.Although the backwater phenomenon is more obvious due to the inflow of two sides than to the inflow of one side,with the increase of the outflow volume and sediment concentration,the outflow of one side is more likely to overflow the embankment.(2)By analyzing the influence of single and double measured inflow of external flood with different sediment concentration on the pulsation intensity of measured sections upstream of the inlet,it can be concluded that under the premise of the same inflow ratio,the influence of single inflow of external flood on the pulsation intensity of characteristic sections upstream of the inlet is greater than that of double inflow.(3)The influence of outflow inflow on the pulsation intensity of the upstream characteristic section near the left bank and the right bank is basically the same,while the influence of outflow outflow outflow on the pulsation intensity of the upstream characteristic section near the right bank is greater than that of the left bank.(4)The turbulent effect of external flood on the main channel water body without sediment carrying is smaller than that without sediment carrying,but there is no obvious linear relationship between the sediment concentration of external flood and the fluctuation intensity in each direction upstream of the inlet.(5)The sediment deposition process of the main channel has certain similarity under different working conditions.The sediment deposition firstly develops from the bank wall of the external flood side to the opposite bank,and then extends upward and downstream after the deposition reaches a certain depth.The topographic deposition process is affected by the distribution of the flow velocity of the main channel.(6)The higher the flood sediment concentration inside and outside a certain range,the closer the initial position of sediment deposition is to the upstream,the depth of sediment deposition is positively correlated with the flood sediment concentration outside a certain range,and the depth of sediment deposition does not increase when it reaches a certain height under the influence of the water level of the main channel,and the sediment deposition does not affect the upstream cross section of the flood inlet section.In addition,the higher the external flood sediment concentration is,the larger the volume of the siltation topography is,and the maximum depth of the siltation within a certain range is closer to the upper reaches,and the siltation range does not extend to the upper reaches after reaching a certain location.