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標題: Numerical Simulations and Parametric Studies on Flume Experiment of Debris Flow
作者: 何世勝
關鍵字: Numerical Simulations
Parametric Studies
Flume Experiment
出版社: 水土保持學系
摘要: This study collected and analyzed large quantities of the experimental results of flume test for the comparisons with numerical simulation. A series of parametric studies were performed to investigate the effects various experimental parameters such as the slope of flume, inflow discharge, materials type of sediment and in-stream transverse structure on the motion and deposition behaviors of debris flow. In spite of some underestimations and deviations were found in the numerical simulations as compared with the experimental measurements, the prediction trends are generally coincident with measurements. Parametric studies indicate that the motion and deposition behaviors of the monitoring point at floodplain adjacent to the flume outlet has great influence on the subsequent overall simulation of those monitoring points along the downstream of floodplain. As the slope of flume increases, the deposition expands and causes the decrease of deposition depth. Meanwhile, it was found that the transverse flow and expansion at the outlet of flume is relatively insignificant. For a specific range of inflow discharge (0.1~0.01cms), the deposition depth is approximately proportional to the inflow discharge. Water is susceptible to separate from the mixture of gravel-type debris flow and it eventually results in a decrease of flow velocity. The moving distance of flowing mass is relatively short in gravel-type debris flow which frequently displays a strong impact force during the flow motion. On the contrary, the clay-type debris flow possesses high capabilities of water retention, flow mobility and transverse expansion. In addition, according to the numerical results, for in-stream transverse structure (such as check dam) with specific height and layout location, it can be found that the sediment retaining rate offered by the structure can reach 68.47% and the deposition area can be reduced to 41.82% of that without transverse structure. In conclusion, this study verifies the feasibility to evaluate the sediment retaining rate of in-stream structure using numerical simulation procedures.
本研究蒐集並整理水槽試驗數據,提供數值模擬之比對,進而對影響土石流運動及堆積行為的各類參數,進行參數研究以檢核其靈敏度,以供未來數值模擬研究之參考。 雖然數值模擬結果與試驗量測資料比較有低估的情況,且有一段的落差。然而在趨勢上,兩者則相當吻合。參數研究結果顯示,渠道出口處之堆積及流動行為對下游各監測點之整體模擬結果具有關鍵性的影響。當水槽傾角增大時堆積範圍將擴大,並造成堆積深度減小且渠道出口處之土石幾乎沒有橫向流動的現象。在特定入流量(0.1~0.01cms)範圍內,堆積深度與入流量大約成正比。礫石型土石流較易脫水減速,流動距離較短,直進性較強;黏土型土石流保水性佳,較具流動性及左右擴散能力。此外,由數值模擬得知,在渠道上游特定點配置特定高度之構造物時,對土石流貯砂率可達68.47%,堆積面積可縮減為原堆積面積之41.82%,由此可確認採用數值模擬程序來推估構造物貯砂效果之可行性。
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