地工袋應用於擋土結構之探討

葉雅芸(Ya-Yun Yeh)

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(2004年)

https://doi.org/10.6342/NTU.2004.02416

摘要

國內現行生態工法，由政府單位所提供之參考圖可發現，所使用之工程材料以石材為主，導致國內石材嚴重缺乏，故須尋求能替代石材之材料與工法。本研究之目的即在探討以地工袋堆疊方式構築之擋土牆，期能藉此減少石材之使用。
為求得設計時所需之地工袋界面強度參數，遂進行地工袋界面直剪試驗。首先，以傳統之小型（10×10×2.5）直剪試驗，選用兩種厚度之聚丙烯不織布與兩種粒徑的砂，以探討地工袋厚度、內填料，以及乾、濕狀態對界面強度之影響。試驗結果顯示，濕狀態下有較大之摩擦角；兩種厚度的不織布地工袋界面，在填裝河砂時，視凝聚力均略大，而薄不織布地工袋界面之摩擦角較厚者略大。以小型直剪試驗結果，進而選用四種不同地工袋，包括兩種不同厚度之聚丙烯不織布地工袋、平織PE地工袋與平織麻布地工袋；袋內填充越南砂，於乾燥狀態下，進行大型直剪試驗（35cm×35cm×60cm），以求得四種不同地工袋界面之強度參數以供設計分析時使用。試驗結果顯示其界面強度，由強至弱依序為：麻布地工袋、薄不織布地工袋、厚不織布地工袋、平織PE地工袋。
將上述實驗所得之結果，以美國混凝土砌體協會（National Concrete Masonry Association, NCMA）所提供之疊塊式擋土牆設計手冊（Design Manual for Segmental Retaining Walls）進行傳統疊塊式擋土牆與加勁式疊塊擋土牆之穩定分析。分析時，牆寬限制於2.5m內，並採用八種背填土壤材料，經運算分析後，在符合各項穩定之安全係數下，提出以上述四種地工袋擋土牆之建議寬度與高度關係圖，以供設計時使用。
分析結果顯示，地工袋擋土牆之可堆疊高度，當地工袋界面強度小時，由界面強度控制；當地工袋界面強度大時，則由牆底滑動破壞控制。當於自立性不佳之土壤，則可改以加勁式擋土牆。

關鍵字

不織布地工袋 ； 麻布地工袋 ； 地工袋擋土牆 ； 直剪試驗 ； PE地工袋 ； 界面強度

並列摘要

From the reference drawings provided by the concerned department of the government, it is found that among the engineering materials which are used most often are rocks while the ecological engineering method is applied, and this phenomenon results in lack of rock materials in the island. Regarding this problem, it is necessary to seek materials in place of rocks. During this research, the author probed into the earth retaining walls built by piled geotechnical sand bags in order to reduce the use of rock materials.
To obtain the interface design strength parameters of the bags, the author performed a series of direct shear tests of the interface of the bags. First, traditional direct shear tests (10cm×10cm×2.5cm) were performed on two kinds of nonwoven polypropylene of different thicknesses filled with two kinds of sand of different grain sizes to see the influence of thickness of bags, filling materials, humidity of filling materials upon the interface strength. The results show that the friction angle in wet condition is bigger than that in dry condition; the apparent cohesion is bigger while river sand is filled, and the friction angle of thin nonwoven polypropylene is bigger than that of thick nonwoven polypropylene. With the results, the author chose four kinds of geotechnical bags including two kinds of nonwoven polypropylene bags of different thicknesses, PE geotechnical bags, and gunnies to proceed large scale direct shear test (35cm×35cm×60cm) to acquire four different interface strength parameters for design. The outcome of large scale direct shear tests show that the interface strength of the mentioned four materials sorted according to strength is gunny, thin nonwoven polypropylene, thick nonwoven polypropylene, and PE geotechnical bags.
After lab tests, the author performed stability analyses of traditional segmental retaining walls and reinforced segmental retaining walls according to “Design Manual for Segmental Retaining Walls” provided by National Concrete Masonry Association (NCMA). In the analyses, the author limited the width of retaining walls within 2.5m and applied eight different back filling materials. After that, the author brought up the relationship charts of recommended height and width of the mentioned four different geotechnical bags for use of design.
The results of analyses show that the available height of the retaining walls is controlled by interface strength while the interface strength is small; while the interface strength is large enough, the height is controlled by the sliding failure in bottom of the walls, and for soils with bad self-sustaining performance, it is better to use reinforced retaining walls.

並列關鍵字

Geotechnical bag retaining walls ； Direct shear test ； nonwoven bags ； gunnies ； PE bags ； Interface strength

參考文獻

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