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  • 學位論文

應用河道穩定指標探討深槽演變之研究

Evaluation of channel meandering by stability index for Lakus Stream

指導教授 : 何昊哲

摘要


臺灣河川具有坡陡流急之特性,河道常發生底床沖淤問題,對河道穩定造成影響同時可能發生沖刷與溢淹堤防之危險。同時臺灣雨豐枯懸殊,颱風洪水事件發生時洪流暴漲猛落,河道之沖淤更加明顯。目前透過數值模擬來討論河道沖淤已成為相關研究的主流,然而數值模擬參數率定需要花費大量時間,且在模擬大尺度河川動床模式時模擬時間較長,無法進行快速判斷。本研究冀望能選定河道穩定指標,使之能夠準確且快速的對河段沖淤情況及穩定性進行初步的判斷,使在洪水事件發生時可以快速確定不穩定河段,在破堤前進行堤岸防護,也可節約成本。 本研究以拉庫斯溪為研究範圍,透過美國墾務局所發展之二維水理輸砂模式(SRH-2D),選取極端降雨事件進行河道模擬。再利用水理輸砂模式輸出之水文參數計算穩定指標進行穩定性分析。本研究利用竇國仁(1956)提出的穩定指標來進行分析,該指標主要是整合底床泥砂起動流速、泥砂粒徑及水深之關係式,其中泥砂起動流速是代表河流運輸能力。本研究通過對河流運輸能力與所運輸之泥砂的大小數量對應變化的比較可以計算底床沖刷與淤積之臨界條件,對河段可能發生沖刷或淤積趨勢進行判斷,根據沖淤量進行穩定性分析。本研究還使用周宜林(2005)提出的穩定指標進行分析,並與勞哈金數與奧爾洛夫穩定指標進行比較,結果表明周宜林穩定指標表現良好,在彎道河段結果優於勞哈金數與奧爾洛夫穩定指標。 通過穩定指標得到的結果與模式模擬結果、實測結果進行對比,結果表明在河段選取的48個深槽斷面中,使用穩定指標判斷出的沖淤趨勢與實測沖淤結果相符合之斷面數量為37個且高於數值模擬預測的結果,因此本研究所提出的穩定指標可以滿足對河段沖淤趨勢進行快速且準確預測之需求。

並列摘要


River in Taiwan is characterized by steep slope and flow velocity, scouring and silting often happens, which may affect the stability of the channels and cause the danger of overflowing dikes. At the same time, typhoon and flood events often occur in Taiwan. When flood events occur, the flood rises and falls violently, and the scouring and silting of channels becomes more obvious. At present, it has become the mainstream of relevant research to determine the erosion and deposition of channel through numerical simulation. However, it takes a lot of time to calibrate the parameters of the numerical simulation, and the simulation time is longer in the simulation of large-scale rivers, so it is impossible to make quick determination. The aim of this study is to select the river stability index, so that it can accurately and quickly make a preliminary determination on the erosion and deposition of the channel, so that the unstable river reach can be quickly identified when the flood event occurs, so as to win time for the protection of the embankment and save the cost. In this study, Lakus Stream is used to simulate extreme rainfall events using the two dimensional hydrological sand transport model (SRH-2D) developed by the U.S. Bureau of Reclamation. Then the hydrological parameters obtained from the simulation results are used to analyze the longitudinal stability of the channel. In this study, the stability index proposed by Dou Guoren (1956) was selected, which discussed the relationship between the starting velocity of sediment and the particle size and water depth of sediment, and the starting velocity of sediment reflected the correlation between river transport capacity. The critical condition of erosion and deposition can be calculated by comparing the corresponding changes of capacity to sediment transport ,with the size and quantity of bedload, and the tendency of erosion and deposition can be determined, and the stability analysis can be made according to the amount of erosion and deposition. In this study, the stability results obtained from the stability index were compared with the model simulation results and the measured results. The results show that in the 48 sections selected from the reach, the number of sections whose scouring and silting trends are consistent with the measured scouring and silting results is 37. The results show that this stability index can meet the demand of rapid and accurate prediction of the trend of erosion and deposition in the reach, and it can be applied to more river tests in Taiwan in the future.

參考文獻


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