堆積顆粒崩落歷程受坡面及底床條件影響之實驗研究

The experimental study of the effects of basal and slope conditions on granular pile collapsing

鐘文欣(Wen-hsin Chung)

指導教授 ： 周憲德

國立中央大學/工學院/土木工程學系/碩士(2012年)

摘要

本研究進行顆粒崩塌之渠槽實驗，探討堆積顆粒破壞過程的流動特性與孔隙水壓力變化。本研究使用細磨石，分別在不同底床條件及不同高寬比(a=hi /?i)之塊體進行顆粒崩塌實驗，顆粒間孔隙含水量分別為飽和與未飽和，並量測塊體內部動態孔隙水壓力之變化並分析顆粒流動特性。
由實驗結果知高寬比、拉門速度與被動破壞型態皆影響顆粒流體化的厚度。堆積顆粒崩落會隨時間改變，而底床條件、擋門(Sill)高度、高寬比及含水量皆對顆粒崩落歷程及堆積型態產生影響。實驗以Voronoï 粒子影像法進行分析，可得到速度場分佈。乾顆粒流動層的速度剖面，較符合穩定堆積流變學SSH的形式；而在飽和濕顆粒中，因受到水的影響，流動層的速度剖面較接近Bagnold的形式。孔隙水壓值與堆積顆粒崩塌型態相關，高強度降雨入滲至土體內部，使得土體內部孔隙水壓上升，是造成坡地崩塌的原因之一。

關鍵字

崩塌 ； 流體化 ； 孔隙水壓 ； 速度剖面

並列摘要

Flume experiment were employed to examine granular collapses by using ballistic mill stone. The flow characteristics and pore water pressure variation during the collapse of particle piles are analyzed. The effect of aspect ratios of the granular piles under different water content both saturated and unsaturated, is examined by measuring the dynamic pore water pressure and the flow characteristics.
Aspect ratio (a=hi /?i), sliding speed and passive failure are all related to the thickness of the fluidization. Both the deposit geometric morphology and landslide process depend on basal conditions, sill height, aspect ratio and water content. The dry granular flow velocity profiles can be described by the Super Stable Heap(SSH) model. While in the saturated granular flows, the velocity profile can be described by Bagnold rheology. The variation of pore water pressure is associated with the particle collapse patterns. Heavy rainfall induced infiltration increases the pore water pressure and may cause slope collapse.

並列關鍵字

collapse ； fluidization ； pore water pressure ； velocity profile

參考文獻

18.周憲德、廖偉民，「孔隙水壓對溪床土石流發生機制之影響」，中華水土保持學報，第二十九卷，第三期，1998 年，第211-217 頁

1.Bi, W., Delannay, R., Richard, P., Taberlet, N., & Valance, A. (2005). Two- and three-dimensional confined granular chute flows: experimental and numerical results. Journal of Physics: Condensed Matter, 17(24), S2457-S2480. doi: 10.1088/0953-8984/17/24/006

2.Capart, H., D. L. Young, & Y. Zech (2002) “Voronoï imaging methods for the measurement of granular flows” Experiments in Fluids. 32(121),121-135

3.Hsu, L., Dietrich, W. E., & Sklar, L. S. (2008). Experimental study of bedrock erosion by granular flows. Journal of Geophysical Research, 113(F2). doi: 10.1029/2007jf000778

4.Ilstad, T., Marr, J. G., Elverhøi, A., & Harbitz, C. B. (2004). Laboratory studies of subaqueous debris flows by measurements of pore-fluid pressure and total stress. Marine Geology, 213(1-4), 403-414. doi: 10.1016/j.margeo.2004.10.016