濕吸力平衡路徑與水入滲對非飽和紅土之影響

Effects of wetting-path suction equalization and water-infiltration on the shear strength of unsaturated lateritic soil

吳永銘(Yung-ming Wu)

指導教授 ： 魏敏樺

國立臺北科技大學/工程學院/土木與防災研究所/碩士(2011年)

https://doi.org/10.6841/NTUT.2011.00253

摘要

在台灣，林口台地主要為風化碎石和卵礫石所組成的紅土，紅土土壤是殘積土的一種，主要分佈於深層地下水位面之上方，使得大部分紅土土壤之飽和度的降低，而形成非飽和的狀態。當土壤非飽和的時候，土壤的張力與吸力將會使土壤顆粒之間拉的更緊密，並且提升土壤剪力強度來維持紅土邊坡的穩定。然而在降雨期間，水入滲到土壤中使得土壤水分含量增加，而造成土壤中的吸力降低，迫使原本緊密的土壤顆粒變鬆散狀態，以導致土壤剪力強度開始減少，因此土壤邊坡可能會沿著潛在的破壞面引發山崩，故研判紅土邊坡的崩塌與破壞通常主降雨入滲有很大的關係。
為了更瞭解紅土區域的邊坡因降雨造成淺層破壞機制，本研究於林口台地取原狀土壤回實驗室進行一系列三軸壓縮詴驗，包括常吸力剪切詴驗與剪入滲詴驗(shear-infiltration test)。剪入滲詴驗的結果將會與常吸力剪切詴驗中獲得的剪應力和破壞包絡面進行比較與探討，並制定剪入滲行為的基本破壞機制，以及發展出剪入滲破壞行為下的強度破壞包絡面。另一方面在剪入滲詴驗中，量測獲得的水體積應變與孔隙水壓力，將採用Meilani al et. (2005)體積變化之理論來進行分析結果，以提供往後能夠模擬降雨入滲對紅土邊坡不穩定之預測方法。

關鍵字

非飽和土壤 ； 剪入滲 ； 應力水平 ； 水體積應變 ； 基質吸力

並列摘要

Linkou plateau mainly weathered rock and gravel composed of clay in the Taiwan, mainly in the deep water table above the surface, making the most of the clay soil of the degree of the saturation of the reduce, the formation of unsaturated state. When unsaturated soil, the suction and tension of the soil will cause between the soil particles pull more closely, and improve clay soil shear strength to maintain slope stability. However, during rainfall, water infiltration into the soil makes increased moisture content of the soil, resulting in reduced suction of the soil, and to tight structure of the soil particles become loose structure, leading to shear strength of the soil started to decrease. Therefore, may be along the potential failure surface caused by landslides in the soil slope.
This study was to take undisturbed soil of the Linkou plateau do series of triaxial compression tests in the laboratory, including constant suction shear tests and shear infiltration tests. Infiltration test results will be with constant suction shear tests to obtain the shear stress and failure envelope with compared, and develop the basic behavior of failure mechanism of shear infiltration, and the development of the shear strength failure envelope under shear infiltration. The other hand, measurement of water volume strain and pore water pressure on the shear infiltration tests, will by Meilani al et. (2005) use to volume change theory analysis to explore, to provide future to simulate the rainfall infiltration instability prediction for the residual soil slope.

並列關鍵字

unsaturated soil ； shear infiltration ； Stress level ； water volumetric strain ； matric suction

參考文獻

[49] 游淳名. (2005). "非飽和紅土剪力強度之研究-以林口台地為例." 碩士論文, 國立台北科技大學土木工程學系, 台北.

[7] ASTM D5298-03. (2003). "Standard Test Method for Measurement of soil Potential (Suction) Using Filter Paper." West Conshohocken. Pa.

[11] Chandler, R.J., and Gutierrez, C.I. (1986). "The Filter-paper Menthod of Suction Measurement." Imperial College of Science and Technology, 265-268.

[14] Fredlund, D.G., and Xing, A. (1994). "Equation for the Soil-water Characteristic Curve."Canadian Geotechnical Journal, 34(4),521-532.

[15] Fredlund, D.G., and Morgenstern, N.R., and Widger, R.A. (1978). "The Shear Strength of Unsaturated Soils." Canadian Geotechnical Journal, 15(3),313-321.