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    Title: 變圍壓三軸試驗對外包加勁砂柱行為之模擬研究
    Other Titles: Triaxial test simulation on geosynthetic-encapsulated sand column behavior
    Authors: 孫強森;Sun, Chiang-Sen
    Contributors: 淡江大學土木工程學系碩士班
    吳朝賢;Wu, Cho-Hsien
    Keywords: 尺寸效應;砂石樁;外包加勁;地工合成材;三軸試驗;變圍壓;Size Effect;granular column;reinforced;geosynthetic;triaxial test;converted confining pressure
    Date: 2012
    Issue Date: 2013-04-13 11:47:41 (UTC+8)
    Abstract: 砂石樁通常用於土壤改良,目的為使基地土壤足以承受上部載重。而眾多土壤改良工法當中,砂石樁改良法施工迅速,除了可以傳遞荷重外,並能加速地盤排水及減少土壤沉陷。砂石樁雖可承受軸向力,但於樁體上部容易因束制力不足而產生破壞。一直以來工程師不斷的尋求對砂樁土體加勁的方式,以提高砂石樁之承載能力。地工合成材具有柔性和抗張能力,多年來已逐漸被應用於砂石樁之加勁用途,研究結果顯示以地工合成物加勁砂石樁後,可有效提高砂石樁之承載力,並減少樁體的側向膨脹。
    本研究利用三軸試驗,探討以變化圍壓的方式代替外包加勁材料於砂柱試體的可行性。本試驗對三種直徑試體(5、7和10 公分),進行外包加勁材料後於固定艙壓下施加軸力;及對未加勁試體於變化圍壓下施加軸力。變化之圍壓乃是從外包加勁試體進行三軸試驗中,所量測之體積應變推估所得。把推估的束縛應力視成加勁材的效應,並依據每軸應變階段之束縛應力增量,施加到未加勁的試體中,試驗當中量測軸差應力與體積應變,最後與外包加勁試驗結果做比較,以觀察變圍壓試驗是否可以模擬外包加勁試驗之應力-應變及體積關係。
    研究結果顯示,隨著初始艙壓由20 kPa增到200 kPa,變圍壓試驗之軸應力比外包加勁結果由高估到低估,最大高估值與最大低估值分別都在直徑5公分試體,以軸應變25%為基準,最大相對差異為 33%。體積應變則均可模擬相同趨勢,以外包加勁三軸試驗之體積應變為基準,其相對差異在9%以內。試體直徑越大,以變圍壓方式模擬外包加勁砂柱之效果越好,在25%軸應變時,直徑10 公分試體之軸應力差異皆小於14%。由此顯示變圍壓方式可代替對外包加勁試體進行三軸試驗,試體直徑越大其試驗結果之代表性越好。
    Encasing the cylindrical granular column with tensile resistant material is proven an effective practice to improve granular column strength. In the laboratory, the triaxial compression test was employed to conduct tests on encased granular column to study the reinforcing effect of the tensile resistant material. This study explores the behavior of geosynthetic-encased sand columns using simplified approach to reduce laborious experimental efforts. The encased column behavior is simulated by applying persistently increased chamber pressure to the column specimen. Triaxial compression tests were conducted on three diameters of column specimens, 5, 7 and 10 cm to study scale effect. The test results indicate that the simplified approach simulates larger diameter encased column well.
    Appears in Collections:[土木工程學系暨研究所] 學位論文

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