應用二維層平均數值模式及孔口流理論公式推估排砂效率之研究

Apply Two-dimensional Layer-averaged Model and Theoretical Orifice Flow Equations to Estimate Desilting Efficiency

10.6937/TWC.202303_71(1).0004

李豐佐(FONG-ZUO LEE)；陳湘盈(SIANG-YING CHEN)；賴進松(JIHN-SUNG LAI)；譚義績(YIH-CHI TAN)；余化龍(HWA-LUNG YU)

導流槽 ； 防淤隧道 ； 二維層平均數值模式 ； 排砂效率 ； guiding channel ； desilting tunnel ； 2DLAM ； desilting efficiency

台灣水利

71卷1期（2023 / 03 / 01）

39 - 50

繁體中文;英文

台灣因為地理及水文條件影響，造成水庫集水區坡陡流急，因而於颱風豪雨時期常有大量土砂沖淤在水庫及其上游河道內，水庫淤積問題造成水庫庫容無法維持，因此如何永續利用水資源及穩定供水，其防治策略為水庫集水區保育及水庫減淤清淤，水庫減淤清淤的方式則有陸面開挖、水中浚渫及水力排砂等方式，然而曾文水庫上游地區各攔砂壩呈現淤滿狀態，水庫年入庫泥砂量推估為560萬立方公尺。為了增加曾文水庫排砂效率，本研究考量曾文水庫防淤隧道前，利用水中浚渫作業建構庫底矩形導流槽，使曾文水庫於颱洪或豪雨期間，將含細粒料之入庫渾水能夠藉由庫底導流槽的設置，使高含砂濃度的入庫渾水流可集中運移到達壩前，並由曾文水庫防淤隧道將泥砂以水力排砂的方式有效排出，減少泥砂於水庫中淤積，達到水庫永續利用的成效。本研究選擇兩場豪雨颱風事件作為二維層平均數值模式（Two-Dimension layer-averaged model, 2DLAM）的檢定驗證案例，應用二維及三維底部孔口流理論公式計算出流泥砂濃度，探討入庫渾水的運移型態，分析防淤隧道排砂效率的變化，由模擬結果顯示，透過二維底部孔口及三維底部孔口公式進行出流泥砂濃度推估，可於退水段反映渾水潭下降之趨勢，因此未來可應用於修正2DLAM數值模式於退水段模擬結果之不足，而當導流槽之長度到達A-10以上斷面時，入庫渾水渾水流不會因長枝坑溪匯流口地形而受到影響，且於導流槽上游入口處泥砂開始集中，並順利運移至防淤隧道口，可使入庫泥砂有效的排出曾文水庫。

Due to the influence of geographical and hydrological conditions in Taiwan, the slope of the reservoir catchment area is steep, and the flow is rapid. Therefore, during the period of typhoons and heavy rain, a large amount of soil and sand is often washed and deposited in the reservoir and its upstream channels. The reservoir sedimentation problem decreases the reservoir storage capacity. In order to ensure water resources utilization and stabilize the water supply, the prevention and control strategies involve the conservation of the reservoir catchment area as well as the desilting and dredging of the reservoir. Reservoir desilting and dredging involve land excavation and dredging in the water. However, the check dam in the upper reaches of the Zengwen Reservoir is silted up, and the annual sediment volume of the reservoir is estimated to be 5.6 million cubic meters. To increase the sediment desilting efficiency of the Zengwen Reservoir, this study considered the dredging in water to construct a rectangular guiding channel at the bottom of the reservoir in front of the desilting tunnel. It is expected that during typhoon floods or heavy rains in Zengwen Reservoir, the muddy water containing refined grains entering the reservoir can pass through the guiding channel at the bottom of the reservoir. The turbid water flow with high concentration in the reservoir can be transported to the front of the dam in a concentrated manner, and the desilting tunnel can effectively discharge the sediment. This approach is expected to reduce sediment deposition in the reservoir and achieve the goal of sustainable utilization of the reservoir effect. This study selected two torrential rain and typhoon events as two-dimensional layer-averaged model (2DLAM) verification cases, and the two-dimensional and three-dimensional bottom orifice flow theory formula was used to calculate the flow sediment concentration. According to the simulation results, estimating the concentration of sediment outflow through the 2D and 3D bottom orifices formula can reflect the trend of decreasing turbid water in the inflow recession period. Therefore, it can be used to correct the deficiencies of the 2DLAM in simulating the inflow recession period in the future. When the length of the guiding channel reaches Section A-10, the turbid water flow into the reservoir will not be affected by the topography of Changzhi Creek confluence. Sediment begins to concentrate at the upstream entrance of the guiding channel and smoothly transport to the desilting tunnel mouth, effectively discharging sediment out of the Zengwen Reservoir.

1. Amini, A.,Heller, P.,De Cesare, G.,Schleiss, A.J.(2014).Comprehensive numerical simulations of sediment transport and flushing of a Peruvian reservoir.Reservoir Sedimentation,211-219.
2. Bradford, S.F.,Katopodes, N.D.(1999).Hydrodynamics of turbid underflows. I: Formulation and numerical analysis.Journal of hydraulic engineering,125(10),1006-1015.
3. Chung, S. W.,Lee, H. S.(2009).Characterization and modeling of turbidity density plume induced into stratified reservoir by flood runoffs.Water Science and Technology,59(1),47-55.
4. Ellison, T. H.,Turner, J. S.(1959).Turbulent Entrainment in Stratified Flow.Journal of Fluid Mechanics,6(3),423-448.
5. Engelund, F.,Hansen, E.(1972).A Monograph on sediment transport in Alluvial Streams.Copenhagen:Teknish Forlag.
6. Fan, J.(2008).Stratified flow through outlets.Journal of Hydro-Environment Research,2(1),3-18.
7. Firoozabadi, B.,Farhanieh, B.,Rad, M.(2003).Hydrodynamics of two-dimensional, laminar turbid density currents.Journal of Hydraulic Research,41(6),623-630.
8. Huang, C. C.,Lai, Y. G.,Lai, J. S.,Tan, Y. C.(2019).Field and numerical modeling study of turbidity current in Shimen Reservoir during typhoon events.Journal of Hydraulic Engineering,145(5),05019003.
9. Hung, M. C.,Hsieh, T. Y.,Wu, C. H.,Yang, J. C.(2009).Two-Dimensional Nonequilibrium Noncohesive and Cohesive Sediment Transport Model.J. Hydraul. Eng.,135(5),369-382.
10. Imtiyaz, Nafeela(2021)。台北，國立臺灣大學土木工程學研究所。
11. Lai, Y. G.(2008).SRH-2D version 2: Theory and User’s Manual, Sedimentation and River Hydraulics–Twodimensional River Flow Modeling.Denver, Colorado:US Department of the Interior, Bureau of Reclamation, Technical Service Center, Sedimentation and River Hydraulics Group.
12. Lai, Y. G.,Greimann, B. P.(2010).Predicting contraction scour with a two-dimensional depth-averaged model.Journal of hydraulic research,48(3),383-387.
13. Lai, Y. G.,Huang, J.,Wu, K.(2015).Reservoir turbidity current modeling with a two-dimensional layer-averaged model.Journal of Hydraulic Engineering,141(12),04015029.
14. Lai, Y. G.,Wu, K. W.(2018).A numerical modeling study of sediment bypass tunnels at Shihmen Reservoir, Taiwan.Int. J. Hydro,2,72-81.
15. Lee, F. Z.,Lai, J. S.,Tan, Y. C.,Sung, C. C.(2014).Turbid density current venting through reservoir outlets.KSCE Journal of Civil Engineering,18(2),694-705.
16. Oehy, C. D.,Schleiss, A. J.(2007).Control of Turbidity Currents in Reservoirs by Solid and Permeable Obstacles.Journal of Hydraulic Engineering,133(6),637-648.
17. Olsen, N.R.B.(1999).Two-dimensional numerical modelling of flushing processes in water reservoirs.Journal of Hydraulic Research,37(1),3-16.
18. Parker, G.,Fukushima, Y.,Pantin, H. M.(1986).Self-accelerating turbidity currents.Journal of Fluid Mechanics,171,145-181.
19. Parker, G.,Garcia, M.,Fukushima, Y.,Yu, W.(1987).Experiments on turbidity currents over an erodible bed.Journal of Hydraulic Research,25(1),123-147.
20. Wu, C. W.,Chou, Frederick N.-F.,Lee, F. Z.(2021).Minimizing the impact of vacating instream storage of a multi-reservoir system: a tradeoff study of water supply and empty flushing.Hydrology and Earth System Sciences,25(4),2063-2087.
21. Wu, H. W.,Tsai, B. S.,Hwang, C.,Chen, G. W.,Kuo, W. C.(2020).Efficiency of the drawdown flushing and partition desilting of a reservoir in Taiwan.Water,12,2166.
22. Young, D. L.,Lin, Q. H.(2005).Two-dimensional simulation of a thermally stratified reservoir with high sediment-laden inflow.Journal of Hydraulic Research,43(4),351-365.
23. 水利規劃試驗所(2020).水庫防淤管理與技術應用.經濟部水利署.
24. 南區水資源局(2022)。,經濟部水利署。
25. 南區水資源局(2021).曾文水庫集水區分流隧道可行性研究.經濟部水利署.
26. 南區水資源局(2013).曾文水庫庫區泥砂濃度觀測站建置.經濟部水利署.
27. 陳湘盈(2020)。台北，國立臺灣大學生物環境系統工程學研究所。