Performance of encased granular columns considering shear-induced volumetric dilation of the fill material

doi:10.1680/gein.12.00029

機構典藏 > College of Engineering > Graduate Institute & Department of Civil Engineering > Journal Article > Item 987654321/80325

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Title:	Performance of encased granular columns considering shear-induced volumetric dilation of the fill material
Other Titles:	考慮受剪引致體積膨脹之外包加勁礫石椿的性能研究
Authors:	Hong, Y. S.
Contributors:	淡江大學土木工程學系
Keywords:	Geosynthetics;Sand column;Numerical analysis;Encased;Triaxial compression test;地工合成材;砂石椿;數值分析;外包;三軸壓縮試驗
Date:	2012-12-01
Issue Date:	2013-01-22 11:32:41 (UTC+8)
Publisher:	London: ICE Publishing
Abstract:	This numerical study investigates the behaviour of geosynthetic-encased sand columns. Based on an elastic-plastic constitutive model used with the non-associated flow rule, the prominent expansive behaviour of medium to dense sands is characterised. Numerical analysis results are verified via laboratory triaxial tests on encased sand columns, where the sand mechanical properties are extracted from simple experimental tests. The tested sand columns in the experiments consist of two sands, encased by sleeves fabricated from two geotextiles. This verification demonstrates that the sand volumetric strain profoundly affects the induced confining pressure of an encased column. Exactly how the encasement stiffness, strength and diameter of the granular column influence encased column response is also studied using numerical analyses. Numerical results indicate that the encasement induces additional confining pressure, subsequently preventing strength yield in the encased columns before the encasement reaches its yield strength. These results further demonstrate that the ratio of encasement stiffness to column diameter significantly affects the response of a granular column. Moreover, it may be unnecessary to encase a small-diameter column with a stiff encasement, whereas encasing a large diameter column with a low-stiffness encasement may produce a limited reinforcing effect. 本文基於彈塑性組成模式結合非諧合流法則，詮釋中至緊砂受剪引致體積膨脹之外包加勁礫石椿的承載性能。研究方法以數值模擬為主，探討影響外包加勁礫石椿力學行為的因素。數值模型藉由三軸壓縮試驗結果經塑性分析，獲取砂石材料之彈-塑性參數；且透過兩種不同砂石及兩種不同加勁材所構成的外包加勁砂柱試驗結果，驗證數值分析模式的正確性。研究結果證實砂石材料的體積應變，對於加勁材作用於礫石椿所引致的圍束應力具有決定性的影響；而較簡易的雙曲線模式雖能精準掌握砂石的應力-應變行為，但卻無法闡述砂石材料於降伏前即有的膨脹行為，導致嚴重低估外包加勁礫石椿的承載性能。此外，也進一步探討外包加勁材的勁度與強度，以及椿體直徑對於外包加勁礫石椿力學反應的影響。分析結果顯示外包加勁材引致的圍束應力增量，於加勁材達降伏強度前抑制外包礫石椿可能產生的降伏現象。另，分析也顯示外包加勁材勁度與椿體直徑的比值，顯著的影響椿體的行為。採用高勁度加勁材包裹小直徑礫石椿，將產生極高的圍束應力，工程應用上可能不需要；然而，採用低勁度加勁材包裹大直徑礫石椿，將因圍束應力增量小而導致有限的加勁效果。
Relation:	Geosynthetics International 19(6), pp.438 –452
DOI:	10.1680/gein.12.00029
Appears in Collections:	[Graduate Institute & Department of Civil Engineering] Journal Article

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