不同粒徑組成之土石流流動特性研究

Flowing Characteristics of Debris Flow with Different Grain Size Compositions

游繁結(Fan-Chieh Yu) ； 賴建信(Chien-Hsin Lai)

《中華水土保持學報》 27卷3期 (1996/09) Pp. 213-222

https://doi.org/10.29417/JCSWC.199609_27(3).0005

摘要

本研究以不同坡度之渠槽試驗，模擬不同土砂粒徑組成之土石流流動現象，並觀測其段波高度、體積濃度與流速，同時追蹤粒子運動之軌跡，以瞭解其流動特性。由試驗結果與分析可瞭解土石流之先端部呈段波之形態流動，其體積濃度較後續流動部分為大，且段波高度愈高，體積濃度亦愈大。並以段波高度對中值粒徑之比值視為段波之特徵高度，以代表流體之膨漲特性，則顯示出混合土砂中粗粒含量較高者，在相同體積濃度下，其段波之特徵高度愈高。而由粒子運動軌跡及粒子碰撞應力之分析，顯示粒子之碰撞作用為支配土石流流動及流體膨漲之應力來源。同時，粗粒含量愈高之土砂組成，其流動之摩擦阻力與碰撞應力均較大，但卻因容易脫水減速而形成間歇性之流動，相對於粒徑小於2 mm之土砂含量超過20%時，則將使土石流段波容易持續流動。

關鍵字

土石流 ； 土石流段波 ； 碰撞應力（分散應力） ； 膨漲流體

並列摘要

To realize the flowing characteristics of debris flow with different compositions of grain particles, debris-flow simulations were conducted in channel flume under different channel slopes and different water discharges. The height, volumetric concentration and flowing velocity of bore wave were measured. during debris flowing. And the particle's movement was also traced with colored particles. According to the analyzed results, it was known that the bore wave was formed on the front of debris flow, and its volumetric concentration was higher than that behind the bore wave. Besides, the higher the bore wave was, the higher the volumetric concentration was. The ratio of bore height to particle's median diameter was regarded as the characteristic height to represent the dilatation of fluid. Therefore, the characteristic height was increased with the higher content of coarser particles under the same volumetric concentration. This meant that the dilating effect was more significant as the content of coarser particle was higher. At the same time, the stress produced from the particles collision which was higher with the higher content of coarser particle, was not only the main factor to support the flowing and dilation of debris flow, but also increased the frictional effect during debris flowing. These kinds of material were easier to dehydrate and form an intermittent flowing. On the contrary, the materials containing more than 20% of finer particles which were less than 2 mm in diameter, would keep the flowing of bore wave continuously.

並列關鍵字

Debris Flow ； Bore Wave of Debris Flow ； Colliding Stress (dispersive stress) ； Dilatant Fluid