不同粒徑組成與土石流發生之關係探討

THE RELATION OF DIFFERENT GRAIN SIZE COMPOSITION ON THE OCCURRENCE OF DEBRIS FLOW

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

《中華水土保持學報》 25卷1期 (1994/03) Pp. 25-31

https://doi.org/10.29417/JCSWC.199403_25(1).0004

摘要

土石流發生之機制相當複雜，以力學分析雖能瞭解土石流發生之條件，但不同粒徑所組成之土體，則因材料特性之影響，可促使土體發生土石流之原因，則非一般之力學性質可完全顯現。因之為瞭解土石流之發生與土砂組成之關係，本研究乃以不同粒徑組成七種試料，並在室內渠槽模擬土石流之發生條件，而獲致土體在粒徑小於2 mm之含量少於20%時，相當容易發生土石流；同時以原推導之公式(1)推導土石流發生之坡度時，若作0.8之修正，可保守的預估其臨界坡度。此外，透水係數乃代表土體孔隙之大小，可影響滲流速度之快慢，而此等流動之速度大小可能對土體中之細粒土砂產生撞擊作用而移動，有助於土石流之觸發作用。惟如何引進滲流流速之因子，以修正(1)式之預估精度，將有待進一步之試驗研究。

關鍵字

土石流 ； 粒徑分佈 ； 透水係數 ； 滲流

並列摘要

The occurring mechanism of debris flow is very complicated. It could not be described completely, even if the theoretical equations have been derived from many theories. Especially, the physical properties of soil body with different grain size distribution which may influence the occurrence of debris flow, is difficultly displayed in a theoretical equation to pridict the occurrence of debris flow. Therefore, a simulated experiment was conducted in the laboratory with seven kinds of soil materials which were composed of different grain size distribution in order to understand the influence of different grain size composition on the occurrence of debris flow. According to the experimental results, it is known that the soil body, with a less than 2090 content of small particle which is smaller than 2 mm in diameter, will easily create debris flow. And the critical slope condition can be estimated by using Eq. (1) with a multiple of 0.8. Besides, permeability coefficient indicates that the pore size controls the seepage flowing rate. And this flowing possibly acts on the small particles to move, then debris flow is induced. But, how to involve the velocity of seepage flow into Eq. (1) is still in need of farther experiment.

並列關鍵字

Debris Flow ； Grain Size Distribution ； Permeability Coefficient ； Seepage Flow