紅土礫石坡受降雨影響之數值分析與護坡工法研究

Numerical Analysis of Lateritic-Gravel Slopes Affected by Rainfalls and Slope Protection Methods

余峻霆(Chun-Tin Yu)

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(2014年)

https://doi.org/10.6342/NTU.2014.00289

摘要

本研究針對紅土礫石坡受降雨之影響進行研究，選擇之地點為雲林縣坪頂村及台中市大肚山之崩塌地為案例，並利用Geo-studio 2007進行降雨入滲之二維數值模擬。雨量資料採用研究區附近之雨量觀測站資料；其中，坪頂村為敏督利颱風資料，大肚山為蘇拉颱風資料。模擬過程中針對自然邊坡及坡內埋設錨碇織網系統受降雨入滲時，土壤之孔隙壓力、剪力強度參數、剪應變、塑性區、邊坡之安全係數等進行探討，並對邊坡整治提出建議。
由分析之結果，坪頂村與大肚山邊坡之土壤：總凝聚力隨著降雨發生皆有下降趨勢，而剪應變以及塑性區主要發展於礫石層靠近坡面部分，為邊坡破壞潛勢之主要區域。此外，利用切片法分析邊坡安全係數時可以發現，坪頂村的礫石層下方為滲透性差之泥岩層，使孔隙壓力較能夠累積，導致降雨後邊坡整體安全係數有較大幅度之下降。而大肚山的礫石層下方甚厚，孔隙壓力較難累積，邊坡整體安全係數下降幅度較坪頂村來的小。而由不同土層內之局部安全係數可以發現，坪頂村與大肚山的礫石層安全係數均較上層之紅土層為低，由此可以推估漸進式破壞之起源及發展。
護坡工法之分析結果則可以發現，錨碇織網系統(AGS)對於提升邊坡安全係數有顯著之影響，因為地工織物可降低礫石層之孔隙壓力，土釘則發揮軸力，使降雨後坡體之塑性區發展均有能大幅減少，故對邊坡整體之穩定有提升之效果。

關鍵字

紅土 ； 礫石 ； 降雨入滲 ； 數值分析 ； 安全係數 ； 錨碇織網系統

並列摘要

In this research, the two sites studied are located at Pingding Village, Yunlin Country and at Mt. Da-Du, Taichung. The slope of the former site is composed of layers of lateritic soil, gravels, and mudstone, from top to bottom; while the latter is composed of only lateritic soil and gravel layers. The 2D FEM code, Geo-studio 2007, was used to simulate rainfall infiltration into the slopes in the analysis. The rainfall data were obtained respectively from Typhoon Mindulle and Typhoon Saola. The changes in the pore pressure, shear strength, and shear strain of the soil, and the yield zones and the factor of safety of the slope were investigated. Moreover, the effect of using a slope protection method, anchored geosynthetics system (AGS), to reinforce gravel slopes was also examined.
From the results of analysis, high shear strain and yield zones would develop in the gravel layer, which indicated that the potential failure zone would be in the gravel layer. Using the slice method for slope stability analysis, different results are found for the two sites due to their geological conditions. For the slope at Pingding Village, water would accumulate on the mudstone layer and thus resulted in lower factor of safety. On the other hand, in the slope of Mt. Da-Du, water would seep into deep depth, and therefore the factor of safety would be less significantly affected. Further, the AGS was found to be able to increase the factor of safety of the slope due to the drainage provided by the geosynthetics and the anchored forces induced in the soil nails.

並列關鍵字

lateritic soil ； gravel ； numerical analysis ； factor of safety ； AGS

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