Turbid water desilting characteristics of circular-ring desilting and sediment ejection basin

Abstract: Circular rings desilting and sediment ejection basin are new secondary sediment treatment facilities, which was first applied in Xinjiang Hutubi Aweitan canal head. Agricultural water was solved emphatically in the Aweitan irrigated area. "Circular rings" have worked satisfactorily since 2006. Taking Xinjiang Hutubi Aweitan "circular rings" as a prototype, the experimental model on turbid water movement characteristics has been studied. Sediment concentration distribution was tested by the computer aided sediment meter of CYS-Ⅲ-Type. The sediment particle diameter was measured in the outflow channel and different radius range of"circular rings. Meanwhile, the desilting rate and water consumption were calculated, as well as the maximum particle diameter in the outflow channel. The research showed that the distribution of sediment concentration, desilting range, desilting diameter and desilting production are non-uniform in the ring direction of "circular rings". However, sediment concentration distribution and particle diameter size are inversely proportional to the radius in the radial direction. Sediment concentration is inversely proportional to water depth in the vertical direction, vertically non-uniform within 1/2 radius. Meanwhile, sediment grain size is crude. In other ranges, vertical distribution is more uniform and sediment grain size is smaller. Distribution of sediment concentration, desilting diameter and desilting production are larger in the range of 135°-225° in "circular rings". Under the design discharge and sediment concentration conditions, the desilting rate is 90.9 percent of "Circular rings". The maximum particle-size is 0.935mm in the outflow channel. The desilting rate for grain which diameter is more than 1 mm is 100 percent, while the water consumption is only 6.6 percent. When considering the annual flow and sediment concentration conditions, the water consumption well is reduced, but the amplitude reduction should be further studied. Discharging of sediment is achieved by means of the water flow energy, steeper inverted cone bottom slope, self-weight sediment, as well as high-speed circulation. The experiment proved that the model test results are in accordance with the prototype in "circular rings". The sorting phenomenon of the sediment particle was obviously existed. Separating water and sediment was decided by gravity sedimentation. One of the most important reasons is that the high desilting efficiency obtained by the long overflow weir. It has a high desilting rate, desilting particle range and low water consumption, especially taking advantage of the draining bed sediment of coarse grain. Meanwhile, automatically discharging of the sediment is achieved by an intermittent way. Therefore, promoting the use of "circular rings" has important significance for improving the agricultural water-saving irrigation efficiency and sufficiently utilizing water resources.