地中壁抗液化行為之數值分析

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题名:	地中壁抗液化行為之數值分析
作者:	楊雁翎;Yang,Yen-Ling
贡献者:	土木工程學系
关键词:	格子狀地中壁;FLAC2D;土壤液化;剪變形;沉陷;grid-wall ground improvement;FLAC2D;soil liquefaction;shear deformation;settlement
日期:	2016-08-24
上传时间:	2016-10-13 12:13:27 (UTC+8)
出版者:	國立中央大學
摘要:	格子狀地盤改良工法為日本近年來所研發的地盤改良工法，利用地中壁將土壤圍束以減少土壤之剪變形與沉陷達到地盤改良之效果。本研究以FLAC2D有限差分軟體分析改變地中壁設計參數對束制土壤剪變形之效果。藉由改變地中壁模型之地中壁間距、壁厚、地中壁有無剛接頂板，以及地中壁有無貫入堅硬承載層之情況，討論地中壁參數對土壤剪變形與沉陷的束制效果。　　研究結果顯示，當地中壁間距小於5公尺時，才有較明顯的束制效果，增加地中壁壁厚，能提高地中壁剛性，故能增加地中壁的束制效果。若地中壁無剛接頂板，圍束區近地表土壤之剪變形反而會大於自由場，究其原因為地中壁與土壤之變形行為不同所致，若加入地中壁剛接頂板，則能有效改善圍束區近地表之剪變形至與自由場相同。在所有情況下，若地中壁有貫入堅硬承載層則能有效提升地中壁對壁內土壤剪變形與沉陷之束制效果。若地中壁內有設置建物之情況，發現設置地中壁能有效改善建物之沉陷傾斜，若地中壁貫入堅硬承載層則建物不會發生沉陷傾斜。 ;Recently, Japanese engineers developed a new ground improvement method, which is called grid-wall ground improvement. The method adopts underground walls to constrain the dynamic shear deformation of soil during earthquake to prevent soil liquefaction. This research uses a two-dimensional explicit finite difference program, FLAC2D to analyze the constraint effect of shear deformation of soil by the underground walls. The design parameters are the spacing, the thickness, the rigidity of the underground walls, and the bearing layer. 　　The result shows that only when the spacing of underground walls is smaller than 5 m, the constraint effect of the shear deformation of soil becomes obvious. The thicker the underground walls, the higher the rigidity of underground walls, the more the constraint effect. In the case of underground walls without top slab, the shear deformation of soil in shallow depth constrained by the walls is greater than the shear deformation of soil in the free field. The reason is the large deformation created at the top of walls which causes surrounding shallow soil having larger shear deformation. In the case of walls with top slab, the shear deformations of shallow soil is more or less the same as the shallow soil in the free field. This is because the top slab constrains the large deformation at the top of walls during shaking. In all the conditions, the underground walls can constrain the dynamic shear deformation of soil very well when the bottom of underground walls are in the bearing layer. If build a construction on the underground walls, it can decrease the settlement and the tilt of the building obviously.
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