土石流支流入匯主河道之泥砂沖淤研究

The Fluvial Processes of Main Channel Induced by the Tributary of Debris Flow

陳樹群(Su-Chin Chen) ； 李仲強(Chung-Chiang Li)

《中華水土保持學報》 37卷1期 (2006/03) Pp. 9-22

https://doi.org/10.29417/JCSWC.200603_37(1).0002

摘要

本研究透過實驗渠槽，探討土石流入匯主河道之泥砂沖淤特性。由實驗發現土石流支流入匯主河的現象可分為兩階段，第一階段為土石流初始進入交匯口流動後停淤之過程，並以因次分析方法，建立支槽溯源淤積前主槽最大淤積泥砂量之估算公式。第二階段為土石流支流開始發生溯源淤積，伴隨支槽泥砂特性發生變化，在溯源淤積過程中會發生第二次土砂流動進入交匯口，堆積扇二次擴張。由實驗觀測可彙整三種主要分類：(1)Type Ⅰ型為支槽水躍捲砂流入堆積扇造成擴張；(2)Type Ⅱ型為支槽新形成之土石流流入堆積扇造成擴張；(3)Type Ⅲ型為支槽擠壓堆積扇造成擴張。藉由實驗觀察與理論分析證明Type Ⅱ型支槽會維持一穩定坡度溯源淤積，並新形成土石流入匯堆積扇。

關鍵字

土石流 ； 溯源淤積

並列摘要

The purpose of this study is to describe, based on the flume experiment, the tributary debris flow which flew into the main channel and deposited on the confluence. This study shows that the formation of the alluvial fan included two primary processes, which are separated by the appearance of the retrogressive deposition in the tributary. Dimensional analysis has been used to show the maximum deposition volume before the retrogressive deposition of the tributary. In the process of the retrogressive depositing, the sediment continues to flow into the confluence in three typical patterns to cause the expansion of the alluvial fan. (1)Type Ⅰ represents that Sediment is swept to the alluvial fan by hydraulic jump. (2)Type Ⅱ represents that a new debris flow, which is formed above the mound of the tributary flows into the alluvial fan. (3)Type Ⅲ represents that the alluvial fan is pushed by the mound of the tributary with stop and go motion due to the excess pressure behind. For Type Ⅱ, the slope of the tributary, which remains the same is proved by theoretical analysis.

並列關鍵字

debris flow ； retrogressive deposition