顆粒性土壤邊坡滑動破壞之力學機制

The Sliding Failure Mechanisms of Granular Soil Slopes

張志銘(Chih-Ming Chang)

指導教授 ： 陳榮河

國立臺灣大學/工學院/土木工程學研究所/碩士(2009年)

https://doi.org/10.6342/NTU.2009.01093

摘要

本研究之模型試驗分為乾砂邊坡滑動破壞和降雨入滲引致之邊坡破壞兩部份；藉由室內物理模型-邊坡滑動試驗儀分上坡、下坡及水平堆積區，以越南石英砂和粉土為試驗材料，探討乾砂滑動行為及降雨入滲引致之邊坡破壞機制。
乾砂滑動破壞之觀察，係使用質點影像分析儀(Particle Image Velocimetry, PIV)，針對坡度、坡高兩項變因進行探討，分析求得滑動深度、衝擊力等參數並根據能量守恆定律與滑動塊體之假設推導出一簡化公式，以推估滑動影響範圍。
入滲試驗模擬前期降雨與地形集水之情形，由上坡平台集水均勻入滲，針對邊坡內部不同地質條件、細料含量及降雨強度，量測探討入滲歷程中水壓、含水量變化與破壞後土體堆積的情形。
試驗結果發現，純砂之邊坡無論是否有設置不透水層，皆為滑動型破壞，均由坡趾處先產生管湧，再以後退式向上坡發展；有不透水層之情況下，破壞較為連續且迅速，破壞時邊坡內部含水量瞬間上升，上下坡交界處於破壞前亦有含水量起伏之情形。
砂土中加入10%粉土時，破壞模式轉為流動型，於上坡面接近平台處產生顯著之沖蝕孔洞，破壞前上邊坡含水量即有異常變化之情形且平台處含水量上升趨勢較純砂試驗明顯。又因流動破壞主要挾帶砂土，故流動性佳、流速快，影響範圍比純砂之滑動型破壞為大。
對較低滲透性之砂質土壤(含10%粉土)來說，降雨強度對邊坡破壞時間之影響並不顯著，受限於材料之滲透性，易於入滲面產生積水並形成地表逕流沿坡面流失，僅部分雨水產生入滲對邊坡破壞造成影響。

關鍵字

模型試驗 ； 砂性土壤 ； 邊坡 ； 入滲 ； 破壞

並列摘要

In order to understand the slope failure mechanism of slopes due to rainfall infiltration, physical models of slopes composed of sand and silt were used to perform tests. Two kinds of model tests carried out in this study were: (1) sliding of dry sand slope, (2) slope failure due to rainfall infiltration.
The particle image velocimetry (PIV) and the impact measurement device were utilized to investigate the impact force and the influencial area of the sliding of dry sand slopes.
Different geological situations, fines content of slope and rainfall intensity were taken into consideration to understand the slope failure due to rainfall infiltration. Water was permeated into the slope from the top. The pore water pressure, the water content and the deposition of soil mass were measured.
Test results show that failure of pure sand slopes was a sliding type. Water flow caused piping at the toe of the slope, and then retrogressed upward along the slope. The water content within slope increased suddenly when the sliding occurred.
The flow type, failure occurred for slopes with 10% silt content, In addition, an erosion hole was observed on the upper slope near the crest. The failure mass contained a lot of water. Therefore, its mobility was better, flow velocity was fast, and the deposition area was wider than those of pure sand slopes.

並列關鍵字

model tests ； sandy soils ； slopes ； infiltration ； failure

參考文獻

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