降雨引致不飽和顆粒性土壤邊坡破壞之模型試驗研究

Laboratory Studies on the Slope Failures of Unsaturated Granular Soil Induced by Rainfall

簡瑋男(Wei-Nan Chien)

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(2010年)

https://doi.org/10.6342/NTU.2010.01478

摘要

諸多前人研究中均指出降雨對邊坡破壞的不利因素。最近十年來，開始有人利用室內模型對降雨引發邊坡破壞進行試驗研究，並於坡體內部埋設監測儀器觀測，其主要方向在於不同給水條件、降雨強度、細料含量、相對密度、坡型尺寸等，且多以击型坡和單一試驗材料下進行試驗，本研究屬於不同細粒料含量下探討邊坡破壞機制，並搭配其它條件，如前期降雨、降雨強度、排水條件、傾斜面岩盤、凹型坡與w凸型坡等，在不同條件組合下，觀察邊坡破壞機制、孔隙水壓與體積含水量變化。
本研究採用自行設計的工業噴霧系統模擬自然降雨，於坡內埋設水份計與孔隙水壓計來觀察破壞過程中體積含水量與孔隙壓力變化，並利用攝影機對邊坡破壞歷程進行紀錄。試驗結果發現：(1)細粒料含量愈多，降雨時坡體土壤體積含水量與孔隙壓力增加較快，破壞過程中之最大孔隙壓力較高；破壞愈早發生、發展速度愈快、長度較長。破壞型式從後退式滑動破壞轉變為泥流破壞，且容易發生管湧破壞，當管湧發生，孔隙壓力在短時間內快速下降。(2)凹型坡破壞較击型坡早發生，靠近上下坡交界處累積較大孔隙壓力。破壞堆積區範圍較击型坡廣、也較薄。(3)降雨強度愈高，孔隙壓力與體積含水量上升較快，破壞較早發生，破壞長度長、深度較深。

關鍵字

模型試驗 ； 水份計 ； 孔隙水壓力 ； 邊坡破壞 ； 細粒料含量 ； 降雨強度

並列摘要

Many previous studies have shown that heavy rainfall reduces slope stability. In the past decade, numerous slope stability studies have been conducted on small model slopes using measurements obtained from instrumentation buried in the model. Previous research focused mainly on the different water supply conditions, rainfall intensity, fine particle content, relative density of soil, slope dimension. Most of those studes were performed on convex slopes using a single sand type. In this study combinations of different variations of conditions such as: fine partical content, rainfall intensity, early rainfall amount, drainage area, slope type (concave slope vs convex slope) and bedrock slope are used to observe the process of slope failure, pore pressure and volumetric water content change. This study used a self-designed industrial spray system to simulate natural rainfall and piezometers installed within the slope to record soil moisture data.
The results showed that: (1) higher fine particle content result in soil volumetric water content and pore pressure increases, which obtain maximum values during slope failure. The fastest and largest landslides were also the earliest to occur. Failure begins as a Circular slump and then transitions into a mud flow. Piping often occurred, and once initiated, pore pressures rapidly declined. (2) Concave slope failure occurred earlier than the convex slope, close to the at the junction between the upper and lower slope in the area of accumulated pore pressure. The debris accumulation area was more wide on the convex slope, but also thinner. (3) As expected, higher rainfall intensity resulted in rapid increases in pore pressure and volumetric water content, moreover failure occurred earlier and failure size increased.

並列關鍵字

Laboratory tests ； TDR ； Pore-water pressure ； Landslide ； Fine-particle content ； Rainfall Intensity

參考文獻

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