A Study On The Deposition Characteristics And Influence Factors Of Main Canal In The Dengkou Pumping Irrigation Region

The problem of sediment deposition in canal is great concerned and committed toresearch and solve in today water engineering filed. We regarded Inner Mongolia Dengkoupumping irrigation area which channel water from Yellow River as the research object, wemeasured the thickness of silting before the intake pumping station before opening andafter stopping pump in four irrigation period in2012and2013, water draw rate andsediment concentration into the canal during the pump working and the sedimentconcentration of each section. According to the hydraulics and sediment movement theory,we researched the problem of sediment deposition at water inlet and main canal.The research content includes the siltation features and into canal characteristics, thesediment transport and deposition characteristics, the sediment concentration variation andits correlation with each influence factors. The results show:(1) The water draw rate, diversion width and the stopping time of the pumping stationare the effect factors for the deposition of water intake. The more water draw rate, thebigger diversion width and the shorter stopping time can lead the thinner sedimentdeposition thickness; The distribution thickness before water intake appears intakeupstream greater than the downstream. That means the main area tend to downstream andthe bigger velocity ratio makes this phenomenon obviously.(2) At the time of the pump station beginning work, the higher distribution thickness,the smaller flow velocity and the bigger diversion width could make the more bedsediment brought into canal. The block sand hom before intake can effectively prevent thebed sediment into the canal.(3) There are three relationships at sediment carrying capacity with flow velocity,suspended flow velocity and incipient velocity, corresponding the canal appears threestatus of erosion, deposition and balance. Corresponding sediment concentration variationcan reveal four states of evolution with distance, which are reduction, increase, gentle andtremendous change. The correlation between sediment concentration and influence factors(flow velocity/U, water depth/h, bed sediment/D50, suspended sediment settling velocity/,suspended sediment median diameter/D50) is studied. The strong to weak correlation orderbetween sediment concentration S and each of the factors is U,, D50bed, h and D50suspend.Sediment concentration is power function correlation with U,, D50suspend, and linearfunction correlation with h, and exponential function correlation with D50bed. (4) The suspended sediment carrying capacity of the total carrying capacity is a largerproportion, the bed sediment carrying capacity is little proportion. Impact of suspendedsediment (bed sediment) carrying capacity is not only the suspended sediment particle size(bed sediment) diameter, when suspended and bed sediment particle size both small,suspended sediment and bed load carrying capacity are inevitable over the large.(5) Van Rijn formula is applied to calculate the sediment carrying capacity, thecalculated result has a good correlation with the measured results. Therefore, we use thismethod to determine the carrying capacity and the deposition calculation.