【摘要】 本文总结水槽子水库泄空冲刷的有关资料与经验.针对目前存在冲刷耗水量大的问题,提出改进的冲刷控制运用方式.指出除坝前水位过高之外,在整个冲刷期间保持施放大流量是导致水耗大的主要原因之一.在以横向补给为主的冲刷阶段,大幅度削减冲刷流量方可避免水量的浪费. 另外,从淤泥滩内孔隙水排出量的角度,通过简化的理论分析,说明短时间的空库将不会导致淤泥性质发生大的变化.更多还原

【Abstract】 The Yili River Hydropower Station, which has four hydropower projects in cascades,is developed between two neighbouring river basins. The Shuicaozi Project, which is the second stage of the cascades, functions as a seasonal storage reservoir and diversion work conveying the discharge from the Yili River to the Xiaojiang River for power production. Since no bottom outlet for sediment flushing was installed, so from the time of impounding of the reservoir in June 1958 up to January 1981, sediment deposited in the Shuicaozi Reservoir totalled 8, 160,000 m3 i.e. 85 percent of its total storage capacity had been lost. For the sake of sedimentation reduction and recovery of storage capacity, the measure of drawdown flushing has been used in the Shuicaozi Reservoir.Based on the analysis of field data and theoretical calculation,the characteristics and rational operation of drawdown flushing in the Shuicaozi Reservoir are investigated.The characteristics of drawdown flushing in the Shuicaozi Reservoir can be summarized as follows: (1) The region affected by flushing, the pool water level for starting retrogressive erosion and the longitudinal profile performed by drawdown flushing are rather fixed. (2) As a coefficient of reservoir emptying a is used for representing the extent of utilization of the flow energy in the drawdown flushing, it is evident that the flow erosion capacity was not fully developed in the past flushing events. (3) In the first stage of drawdown flushing,the sediment sluiced comes mainly from the deepening of the main channel on the reservoir bed, and afterwards, sediment sluiced out from the reservoir comes mainly from the banks of the main channel in the manner of slope sliding and bank collapsing. (4) On the top-set of the delta, deposition in the main channel can be sluiced out in drawdown flushing, but upon the flood plain the deposition is accumulated gradually. On the front-set of the delta and in the deposition reach in front of dam where the river valley is narrow, as the main channel is deepened in flushing, the unconsolidated silt slides towards the main channel slowly, the elevation of the deposited reservoir bed can be lowered down in the whole cross-section.The occurrence of channel bank sliding and unconsolidated mud flow is closely related to the pore water pressure in the deposit. The calculated theoretical results show that the quantity of seepage water from the deposit is very small in a period of several days, and the pore water pressure keeps approximately its original value in the drawdown flushing process.The calculated theoretical results obtained from the application of a parabolic partial differential equation show that if the discharge, duration and water volume used in flushing event are kept constant, the larger the drop of water level in front of the dam, the larger the quantity of eroded sediment will be, and the faster the drawdown rate of pool water level, the greater the quantity and intensity of erosion will be.The operation of drawdown flushing in the Shuicaozi Reservoir is suggested as follows: (1) In drawdown flushing, the pool water level in front of the dam should be fully drawn down. ( 2 ) A saddle shaped discharge hydrograph for drawdown flushing should be used. That is, in the first stage, a large flow discharge is used for drawdown flushing, it aims to deepen the main channel. Then, as soon as the main channel is formed the flushing discharge should be cut down. Finally, the large discharge erosion process is repeated, it aims to sluice out the accumulated sediment from slope sliding and bank collapsing and to enlarge the cross-section of the main channel.The suggestion stated above was adopted by the Yili River Hydropower Plant in the drawdown flushing in February 1984, the practice indicated that the silt concentration in the flushing flow was increased and the water consumption of drawdown flushing was reduced obviously.更多还原