- 期刊
應用庫底沖刷槽導流牆減緩水庫淤積之研究
STUDY ON THE APPLICATION OF FLUSHING CHANNEL WITH GUIDE WALL TO REDUCE SEDIMENTATION IN A RESERVOIR
摘要
為探討應用沖刷槽導流牆設置對於減緩水庫淤積效應及壩前出水工排砂效率之影響，本研究以Surface Water Modeling System（SMS）及二維水理泥砂數值模式（SRH-2D），建置阿公店溪上游水庫模型，並納入考量庫區沖刷槽導流牆設置前後之數值地形，設計不同出流水位之水文模擬情境案例，以動床模式模擬阿公店水庫庫區中水砂運移及於溢洪管出流之情形，以及出流泥砂濃度變化。本研究以重現期Q_(1.11)作為本研究之模擬水文情境，進行庫底沖刷槽導流牆減緩水庫淤積之研究，但在阿公店水庫有無具備沖刷槽導流牆且在起始水位EL.28m及EL.30m情境下，兩種起始水位排出渾水濃度差異並不明顯，低水位之排砂效益略高於高水位0.71%至2.82%之間，但出流泥砂濃度尖峰值均可達2萬mg/L以上，且排砂效率均可達60%以上，因此，在沖刷槽北側或是南北側皆佈置導流牆後，溢洪管排砂效率分別平均可提升約13%及17.5%。由此可見，利用佈置導流牆方式所建置之沖刷槽，可提升阿公店水庫約13%以上之排砂效率。然而設置沖刷槽導流牆後，由於主要入流泥砂濃度可集中於沖刷槽內，因此雖然溢洪管出流泥砂濃度有升高之趨勢，亦導致沖刷槽內有淤積潛勢，因此建議每年的機械清淤可優先針對沖刷槽內淤砂進行清除，可增進汛期時水力排砂之防淤成效。
並列摘要
This study investigates the effects of implementing a flushing channel with guiding walls on reducing reservoir sedimentation and improving the desilting efficiency of sediment removal in front of the dam. This study built an Agongdian Reservoir model using the Surface Water Modeling System (SMS) and the two-dimensional hydraulic and sediment transport model (SRH-2D). The numerical terrain before and after the installation of the guiding wall was considered in the hydrological simulation scenarios with different outflow water levels. The dynamic bed model was used to simulate the sediment transport in the reservoir and the sediment concentration changes at the outlet spillway. The study used the Q_(1.11) return period as the hydrological simulation scenario to study the effectiveness of the guiding wall. However, the differences in sediment concentration at the outlet spillway for the EL.28 m and EL.30 m initial water level scenarios were insignificant, and the desilting efficiency at the low water level was slightly higher than that at the high-water level, ranging from 0.71 % to 2.82 %. The peak sediment concentration at the outlet spillway exceeded 20,000 mg/L, and the desilting efficiency reached more than 60 %. Therefore, after installing the guiding wall on the north or south sides, the desilting efficiency of the spillway could be increased by an average of approximately 13 % and 17.5 %, respectively. However, after installing the guiding wall, the sediment concentration of the main inflow could be concentrated in the flushing channel, which led to an increasing trend of sediment concentration at the outlet spillway and posed the potential for sediment accumulation in the flushing channel. Therefore, it is recommended to prioritize the mechanical dredging of the sediment in the flushing channel every year to enhance the effectiveness of hydraulic sediment removal during flood season.