土石流體之流變性質是研究土石流流動特性的重要參數之一，但由於測量上的限制，傳統的流變器不適合用於現地泥石漿體流變參數的量測，為此，前人曾利用 L-Box 坍流試驗間接推估漿體之流變參數，並發現 L-Box 試驗中漿體之坍流程度不僅由流變參數所控制，也取決於 L-Box 閘門開啟的速率。
　　本研究利用小型 L-Box 進行細泥漿體之坍流試驗，並使用三維計算流體力學軟體 FLOW-3D 進行模擬，探討利用 FLOW-3D 模擬實際漿體坍流之可行性，而後依據 FLOW-3D 數值模擬結果，分析(1)不同閘門速率對漿體流動剖面之影響、(2)不同閘門速率下，不同黏滯係數之漿體對流動剖面之影響，以及(3)不同閘門速率下，不同屈服應力漿體對流動剖面之影響。
　　本研究結果顯示：數值模擬結果與試驗結果相當一致，說明利用 FLOW-3D 模擬 L-Box 坍流試驗有其可行性。本試驗材料（細泥漿體）經測量之流變特性符合 Schwedoff-Bingham 模型，但由模擬中得出，細泥漿體在流動過程中具有較高的剪應變率（大於10 1/s），故在 L-Box 數值模擬時可直接假設其流變曲線為Bingham模型。此外，由模擬和試驗中發現，當漿體屈服應力低於 20 Pa 且黏滯係數低於 0.5 Pa.s 時，會因其低塑性而坍流至模型端壁造成反彈，影響試驗結果。
　　最後，在本研究著重的討論項目中證實，閘門開啟的速率會對小型 L-Box 之坍流結果造成影響，但該影響僅在一速度區間內作用，若閘門速度快（慢）於此範圍，則不再影響其最終流動剖面。而在流變參數上，閘門速率對坍流程度造成之影響，相對於黏滯係數有一上限值，而對屈服應力則有一下限值，換言之，若流變參數高於某一臨界黏滯係數（或低於某一臨界屈服應力），則閘門速率就不再對流動剖面造成影響。

The L-Box experiment is a method for indirectly estimating rheological parameters using the degree of slurry slump-flow. However, previous studies have found that the slump-flow of the slurry in the L-Box experiment is not only controlled by rheological parameters, but also affected by the sluice-gate opening speed. In this study, FLOW-3D is used to simulate the Smaller L-Box (henceforth referred to as L-Box)experiment with the material as sediment slurry, to study the feasibility of using FLOW-3D to simulate the L-Box experiment, and to analyze the relationship between the pair of sluice-gate opening speed and different rheological parameters. The results show that it is feasible to use FLOW-3D to simulate the L-Box experiment , and the sluice-gate speed will indeed affect the experimental results of the L-Box, but the effect of the sluice-gate on the slump-flow has an upper and lower limit on speed. In addition, if the rheological parameters are higher than a certain viscosity coefficient (or lower than a certain yield stress), the gate speed will no longer have an effect on the flow profile(slump-flow).

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