非飽和低塑性粉土/黏土剪力強度之探討

Shear Strength of an Unsaturated Low Plasticity ML/CL Soil

曾煒迪(Wei-Di Tzeng)

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(2012年)

https://doi.org/10.6841/NTUT.2012.00345

摘要

近年台灣因氣候變遷導致豪雨不斷，加上都市地區發展有限，逐漸向山坡地開發建設，以至於邊坡崩塌危及到人民安全之案例增多。民國97年9月28日，台北市文山區貓空纜車T16塔柱下方邊坡，在連日豪雨下發生山崩，影響到附近社區居民之安全。由於邊坡地表面與地下水位之間的土壤為非飽和狀態，當雨水從邊坡表面開始入滲到下層土壤時，會使得土壤含水量增加、基質吸力下降、孔隙水壓力上升，剪力強度減少，當土壤剪力強度降低到無法支撐土體自身重量和外加雨水重量時，易容易使邊坡沿著潛在破壞面發生崩塌行為。因此，在工程設計與防災設計時須考慮降雨入滲到非飽和土壤中對邊坡之影響。
本研究主要在探討貓空T16塔柱下邊坡之崩塌土層，在雨水入滲下對於邊坡非飽和粉土/黏土剪力強度之影響。本研究首先取得現地土樣，進行基本物理試驗與土壤水份特性曲線，瞭解土壤之物理性質與土壤在非飽和狀態下之基質吸力，並將現地擾動土樣製成重模試體，由一系列三軸試驗，如三軸常吸力(CD)試驗與三軸剪入滲試驗來獲得土壤力學性質參數與入滲行為下的破壞包絡面。

關鍵字

非飽和土壤 ； 三軸常吸力試驗 ； 三軸剪入滲試驗 ； 粉土/黏土

並列摘要

The increase of landslide events in recent years was mostly caused by heavy rainfall as a result of extreme climate change. On 28th September, 2008, a heavy rainfall led to the failure of the slope next to tower T16 of Maokong Gondola in the Wenshan District area of Taipei city. Water from the ground surface infiltrated into the initially unsaturated slope and caused its moisture content to increase and, subsequently, its matric suction to decrease. As a result, the shear strength of the slope dropped and thus triggered the landslide. It is thus important to consider the water infiltration effect during the design of slopes.
This study investigates the effect of water infiltration on the shear strength of unsaturated low plasticity ML/CL soil obtained from Maokong landslide. A series of laboratory tests including the physical test, soil water characteristic test and triaxial shearing test were conducted in order to understand the characteristics of the soil in an unsaturated condition. The shear strength obtained from the constant suction triaxial shearing test was then quantitatively compared with the shear strength obtained from the triaxial shearing-infiltration test. Their corresponding extended Mohr-Coulomb failure envelopes were then proposed.

並列關鍵字

unsaturated soil ； constant suction shearing test ； shear-infiltration test ； ML/CL

參考文獻

[56] 鄭雅仁. (2009). "台灣部分地區土壤水份特性曲線之預測." 碩士論文, 國立台北科技大學土木工程學系, 台北.

[42] 吳永銘. (2011). "濕吸力平衡路徑與水入滲對非飽和紅土之影響"碩士論文, 國立台北科技大學土木工程學系, 台北.

[41] 李世傑. (2008). "以三軸試驗探討非飽和紅土之力學行為." 碩士論文, 國立台北科技大學土木工程學系, 台北.

[61] 鐘雅蘭. (2010). "猴山岳邊坡樹木生長方向的統計分析.",碩士論文,國立台北科技大學土木工程學系,台北。

[57] 趙宥睿. (2012). "數值地形模型精度評估及應用-以猴山岳地滑區為例." 碩士論文, 國立台北科技大學土木工程學系, 台北。