以小尺度模型實驗模擬土石流形貌變化與流變參數之關係

Abstract

本論文的研究目標是想要了解土石流自峽谷流至堆積扇之流變與地貌關係。以小尺度的實驗進行研究，使用不同比例的高嶺土、河床溪砂和水之混和物代表具有高黏滯性的土石流，在此我們進行了兩系列的實驗，分別改變土石流之含水量及顆粒含量以進行比較。 為記錄土石流高速移動與地形快速之變化過程，故使用一特殊旋轉工具將影像成功轉換至三維座標系統，進而取得正確的地形變化情況，同時也記錄土石流的流動狀況。根據多次實驗結果，可將實驗結果分為兩部分進行討論，一部分為渠道內的行為變化，除了討論實驗間參數的影響外，我們使用了運動波法模擬土石流流動之形貌，並且與現地峽谷進行比較，而在峽谷至堆積扇的反應，我們可以推測土石流可分為兩段流動情況，一為快速流動時期主要將土石流的影響範圍向前擴大，另為慢速流動時期主要將影響範圍往左右擴大並且向上堆積，隨著含水量的增加或是顆粒含量的減少我們可以發現快速流動時期的延時拉長，而慢速流動時期的延時則縮短，造成在左右方的堆積較不明顯而縱向的影響範圍拉長，而含水量較低的土石流則有相反的反應。將實驗結果和現地進行定性的比較，同樣的現象均可在現地和實驗結果中發現。

The aim of this thesis is to understand the relationship between rheology and morphology for debris flow going from a narrow valley to a fan. In micro-scale experiments, Kaolinite, black sand and water are mixed to represent debris flows of high viscosity. We change two parameters which are water content and the coarse particle content to observe variation in debris flow behavior due to changes in composition. To measure the fast flow and rapid deformation of the flow surface, a fast scan method using a high speed camera and rotating laser are developed. The results of the experiments are analyzed in two parts, one is channel flow behavior and another is the canyon-fan transition. In channelized results beside compare the experiments, we use kinematic wave to simulate the surge process in channel, and compare the cross section in field. At the canyon-fan transition, debris flow deposit in two stages. In the first stage, a high speed front advance on to fan. In the second stage, the slower tail tends to spread laterally. Increasing water content and decreasing coarse particle content makes the first stage longer and the second stage shorter. As a result, lateral deposits are few pronounced. Finally, the experimental results are compared with field observations.