Determination of the time of lowering depression surface in transition zones with a smooth and instantaneous decrease in water level in reservoir

Abstract

The Republic of Uzbekistan pays great attention to the development and implementation of a program for the development of hydropower based on ensuring the share of hydropower in the energy potential and the integrated development of hydropower potential. Over the last three years, hydropower plants have been built or reconstructed in more than a dozen small and medium-sized earth dams to accomplish this task. Typically, unstable filtration is observed in the body of earth dams because of deviations from the normal filling and emptying of water reservoirs. The main goal of the research is to determine the time to lower the depression surface in the Tupalang earth dam transition zones, which characterizes the intensity of unstable filtration during a smooth and sudden drop in reservoir water level. The calculations were made according to the theoretical dependences of V.P.Nedriga for two cases of smooth and sudden lowering of the water level in the reservoir, starting from the normal backed level (NBL). In the calculations, the values of the main parameters were taken to be the coefficient of water loss of the soil (0.3), the coefficient of filtration of the transition zones (9.5 m/day), and the coefficient of laying the slope of the transition zones (0.2). Calculations showed that the time of lowering the depression surface in the transition zones with a gradual decrease in the water level in the reservoir was 84.1 days, and with an instantaneous decrease in the water level during the operation of a dam with a height of 120 m 3.86 days, and during the operation of a dam with a height of 185 m 6.82 days.