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    Please use this identifier to cite or link to this item: http://tkuir.lib.tku.edu.tw:8080/dspace/handle/987654321/87845

    Title: 軟弱黏土層外包加勁砂柱承載行為之模型試驗
    Other Titles: Model tests of geosynthetic-encased sand columns on loading-settlement behavior in soft clay
    Authors: 余易昇;Yu, Yi-Sheng
    Contributors: 淡江大學土木工程學系碩士班
    洪勇善;Hung, Yung-Shan
    Keywords: 軟弱黏土;砂柱;外包;地工合成材;模型試驗;Soft clay;sand column;Encased;geosynthetic;Model test
    Date: 2013
    Issue Date: 2013-04-13 11:48:00 (UTC+8)
    Abstract: 軟弱地盤為了增加土壤承載力常採用土壤改良方法,而砂柱具備施工快且經濟的地盤改善優勢。近幾十年來,已證實除了可提高土壤承載力、加速黏土層壓密沉陷外,亦可以有效地降低地盤液化的潛能。傳統砂柱雖然可承受上方構造物給予的軸力及剪力,但砂柱應用於軟弱黏土層時,砂柱樁體上部分易因周圍軟弱土壤提供的束制力不足而產生腫脹破壞。利用具有抗張特性的地工合成材包裹砂柱外圍,以增大砂柱的束縛應力,提升砂柱承載能力,即為可行且有效的解決方法。
    In order to increase the bearing capacity is often used the soil improvement methods in soft ground. The sand column is a rapid and cost-effective construction method for improvement of weak soils. In recent decades, the sand column has been verified can effectively providing higher load-carrying capacity, accelerating soil consolidation, and reducing the liquefaction potential. However, insufficient lateral support at a shallow column depth often caused bulging failure in the top portion of the column. The bearing capacity of a sand column is increased by encapsulating the column with geosynthetics that is feasible and effective solution.
    In this study, the model tests on single geosynthetic-encased sand columns installed in very soft clay was used. In order to the model test results correspond with the field columns behavior. Selecting the appropriate modeling material through dimensional analysis method of model similar law is used. The model tests were conducted on five different stiffness reinforcement for encased sand columns. The clay layer, sand layer, and un-reinforcement column for load - deformation behavior was also evaluated.
    The model test results show that encased sand columns can be significantly to enhance the bearing capacity on soft clay. The higher stiffness of the reinforcement caused the smaller the lateral expansion of the column and the larger carrying capacity. The relative assessment of the load-carrying capacity for different reinforcement and a contrasting evaluation of column failure mechanism in the different cases, are salient features of this study.
    In addition, exactly how to get the variation of confining stress in soft clay layer is interpret based on the theory of cavity expansion. The increase in axial deformation causes lateral column expansion and compression of the surrounding soft clay, subsequently causing circumferential stress from the reinforcement; meanwhile, compression of the surrounding clay induces additional earth pressure to act on the column. The analytical results close to the experimental observations. This study provides the estimation of bearing capacity for encased sand columns in soft clay layer.
    Appears in Collections:[Graduate Institute & Department of Civil Engineering] Thesis

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