Study On Ultimate Erosion Depth And Its Mechanism In Downstream Of Navigation-power Junction

Research on the ultimate erosion depth in the downstream of a navigation-power junction was performed based on the basic data extensively collected from the related project and from the domestic and oversea research results. The methodology of research work is a combination of field investigation, data analysis, theoretical study, flume experiments and numerical model tests. Following achievements have been obtained: (1)Flow velocity when water surface is rising and droping, surface slope, variation characteristics of sediment transport rate and its main affecting factors during a flood process are analyzed and the hysteresis effect of sediment transport during flow acceleration and deceleration is revealed; (2) The maximum erosion in the downstream of a navigation-power junction usually occurs in the vicinity of the dam, the erosion depth usually does not exceed 2-3m and the drop of water level is smaller than the river bed erosion, usually not more than 2.0m; (3) Methods to calculate the size distribution of bed load and the thickness and size distribution of the coarsened armor layer have been presented, estimation formula of erosion depth and water level drop have been proposed, and the parameters involved in the formula are discussed, reducing to the formation of a relatively complete methodology of calculation; (4) The treatment mothds are proposed for prediction in engineering application and the concept of'equivalent discharge'is proposed for the equivalent sediment transport of the real peak discharge process, which is a good resolution of the problems; (5) By using the mathematical model and the achievements of the present study, the maximum erosion depth in the downstream of the dam is predicted for the related project, higher agreement has been obtained.