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題名 | 降雨引發淺層邊坡破壞機制=Mechanisms of Rainfall-induced Shallow Slope Failures |
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作 者 | 黃景川; 駱建利; 朱奕璋; 胡立康; 李金龍; 張家薰; 雲世傑; | 書刊名 | 中華水土保持學報 |
卷期 | 42:3 2011.09[民100.09] |
頁次 | 頁184-195 |
分類號 | 434.273 |
關鍵詞 | 淺層邊坡破壞; 降雨; 人工降雨試驗; 含水量; 孔隙水壓; 地下滲流; 滲流分析; Shallow slope failure; Rainfall; Artificial rainfall test; Water content; Porewater pressure; Subsurface flow; Seepage analysis; |
語文 | 中文(Chinese) |
中文摘要 | 豪雨中源頭邊坡之大量崩塌常成為土石流之主要土石來源。對於源頭邊坡破壞機制之了解有助於提昇土石流發生預測準確性。有鑑於國內對於豪雨導致淺層邊坡破壞之實驗研究較有限,本研究進行三個不同尺寸砂土有限邊坡之人工降雨試驗,並量測邊坡破壞伴隨之土砂排出量與邊坡內部含水量及孔隙水壓反應。本研究以邊坡破壞之頭部張力裂縫發展及土砂排出量為邊坡在豪雨中「外部反應」之量化指標;以邊坡內部之含水量與孔隙水壓之消長為「內部反應」之量化指標,嘗試建立邊坡在豪雨滲透與破壞過程中「內部反應」與「外部反應」之關聯性。本研究發現,不透水岩盤與邊坡土壤交界面上之含水量 vs. 時間曲線上之第二個急驟斜率變化點為土壤達到飽和點,且為岩 ~土界面之側向飽和滲流之開始點。此一側向滲流之開始點與邊坡坡趾破壞,土粒大量流出之開始點極為接近。本研究對於試驗邊坡材料建立土 ~水特徵曲線與未飽和滲透係數函數,以有限元素分析程式 (SEEP/W) 對中型邊坡進行模擬分析。結果証實,淺層邊坡中,岩 ~土交界面上一致向外之飽和側向滲流之形成為坡趾附近孔隙水壓急劇昇高之開始,與邊坡之人工降雨試驗觀測之岩~土界面流發生時間相當一致。 |
英文摘要 | Knowledge of the mechanism of rainfall-induced shallow slope failures is essential for increasing the accuracy of debris flow initiation prediction. This paper presents experimental and analytical results obtained from a series of artificial rainfall tests on sandy slopes with various scales. The responses of water content and porewater pressure are used as the index of 「internal response」 of the slope. The「external response」of the slope subjected to rainfall is defined as the volume of discharged sand or the retrogressive development of the tension crack (or scarp). It was found the time of debris discharge initiation is close to that of the formation of a saturated lateral subsurface flow along the soil-bedrock interface, which is signaled by the abrupt transition points of water content and porewater pressure response curves measured at the soil-bedrock interface. This observation was supported by numerical analysis using a finite element program with calibrated soil-water characteristic curves and soil permeability functions. |
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