打樁引致非均質土層地表振動數值之模擬

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題名:	打樁引致非均質土層地表振動數值之模擬
作者:	趙友瑋;Yu-Wei Chao
貢獻者:	土木工程研究所
關鍵詞:	彈塑性分析;黏滯邊界;彈性分析;viscous boundary;inelastic analysis;elastic analysis
日期:	2004-06-23
上傳時間:	2009-09-18 17:14:56 (UTC+8)
出版者:	國立中央大學圖書館
摘要:	本論文主要研究內容為以三維有限元素法之打樁程式模擬在不同性質的土層打樁過程。土層的底部假設為堅硬的岩盤，土層側向則假設延伸至無窮遠處，並以黏滯邊界模擬之。土壤以八節點的塊狀元素模擬，而樁基礎則是用三維梁元素來模擬，至於土壤的非線性行為則假設遵循Mohr-Coulomb降伏準測。藉著對打樁造成周圍地盤受震歷時反應和速度等高線分佈情況的歸納分析,本研究獲致如下的結論： (1)打樁時使用彈性分析則有偏於保守的情形，當樁貫入土壤越深時或離樁越遠時，使用彈性分析與彈塑性分析的結果會很相似的。 (2)土層構造對打樁引致的地表震動特性會有影響，所以在使用衰減公式時，需了解工址土層的性質特性。 (3) 若打樁時鄰近土層中含有岩石，則在樁遠離岩塊處的一側會出現反射現象，大部份的能量會分佈於此，而樁與岩石間速度變化極為複雜，但其速度反應皆會比均質土層的反應還要小。 Adopting a three-dimensional nonlinear finite element model, this study investigates the ground motions induced by pile-driving process in different ground conditions.The soil stratum in underlain by a rigid bedrock and the lateral infinite extent of soil is simulated by viscous boundary. The soil is described using 8-node brick element and pile modeled as 3-D beam element .The nonlinear soil behavior is assumed to follow Mohr-Coulomb criteria . Through the analyses of time history of ground motion and contour of velocity on the surface obtained from parametric study, the following conclusions can be drawn. (1)The result obtained using elastic analysis is conservative. However, as the pile penetrates deeper and the distance from the pile becomes longer, the differences between elastic and inelastic analysis are negligible. (2)The structure of soil stratum has significant effects on the pile-driving induced ground motion, and it is important to choose the empirical formula that is similar to the site. (3)If there is a rock near the pile-driving site, the side opposite to the rock will have larger energy because of reflection of energy due to existence of rock. The change of velocity between pile and rock is complicated but the velocity is smaller than that of soil stratum without rock.
顯示於類別:	[土木工程研究所] 博碩士論文

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