打樁引致地盤振動之數值模擬; Numerical simulation of ground vibration due to pile driving

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Title:	打樁引致地盤振動之數值模擬;Numerical simulation of ground vibration due to pile driving
Authors:	莊家瑄;Chia-Hsuan Chuang
Contributors:	土木工程研究所
Keywords:	數值模擬;衰減;地盤振動;打樁;pile driving;ground vibration;attenuation;numerical analysis
Date:	2003-06-18
Issue Date:	2009-09-18 17:10:20 (UTC+8)
Publisher:	國立中央大學圖書館
Abstract:	台灣地區地狹人稠，發生因施工振動或地盤變位致使鄰近結構物損壞之案例時有所聞，而各種施工振動中，以打樁引致之地盤振動最顯著，對鄰近結構物影響也最大，因此成為最被關心的研究重點。蒐集整理海埔新生地與沖積地盤之打樁振動量測記錄，建立振動量隨距離衰減之統計經驗關係以及結構物之彈性設計反應譜，結合打樁振動管理值與振動量衰減關係，本研究建議出初步的打樁安全距離供參考。結合各振動方向之結構物損害準則與設計反應譜以及振動量衰減關係，提出一打樁振動對建築結構物影響之反應譜分析模式，以更準確地決定打樁安全距離，供工程界參考應用。相對於現場全尺度振動量測資料相當稀少珍貴，且試驗結果常因地因施工而異，較難提供打樁引致地盤振動機制的基本瞭解，數值分析方法是提供對打樁引致地盤振動機制瞭解的另一種選擇。本研究主要分析工具為ABAQUS有限元素分析軟體，將打樁振動問題模擬成單樁承受垂直向衝擊荷載，將應力波傳至週遭地盤之動力問題。此類問題可簡化成為軸對稱二維動力分析模式，大量簡化計算工作量。經由適當地選擇邊界條件、樁、土之參數性質，可相當程度地反應現地之行為。分析結果顯示打樁時距離樁身越近及貫入深度越深，其能量越集中在某一頻率範圍，即顯著頻率範圍越明顯，多在10?20Hz之間。由加速度反應譜可知道打樁振動峰值偏低週期處，此部分與文獻中實地量測結果相同，打樁振動對一般低層結構物與牆的影響較大。 With the cramped spaces and the high population in Taiwan, the structures near the construction site are probably damaged by constructing vibration or the ground deformation. In the various kinds of constructing vibration, the vibration of pile driving is the most important one and has a conspicuous effect to the nearby structures. That’s the reason why a lot of researches focused on this issue. The vibration records of pile driving in the hydraulically reclaimed and alluvial grounds were collected and analyzed to derive the vibration attenuation relations and the response spectra. Based on the criterion and relations, we obtain the safe pile driving distances for the various structures. Incorporating the structural damage criteria for vertical and horizontal vibration directions, the design response spectra and the attenuation relations, a response spectral analysis method was proposed to more accurately determine the safe pile driving distances. The numerical analysis is another choice to understand the ground vibration caused by pile driving in addition to the rare data of full-scale vibration measurement. The analysis tool we use is ABAQUS, which is a finite-elements program. By using this program, the pile driving vibration, which is caused by the vertical impact loading exerted on the top a single pile, propagating to nearby ground is simulated. Therefore, the problem can be simplified to a 2D axis-symmetric dynamic analysis model to reduce the computing work. After choosing appropriate boundary conditions and material properties of piles and soil, the behaviors of ground vibrations are reasonably displayed. The analysis results of ground vibration caused by pile driving are that the vibration energy obviously focuses on some frequency bands when driving pile at near distance and at deeper depth. It means that in these cases, predominant frequency is more significant, and the frequency range is within 10~20 Hz. From the normalized response spectrum, we know that the peak value of spectrum value for pile driving occurs at shorter period. The result is the same that measured at field site. This causes a greater damage potential to lower structures and walls that have shorter fundamental vibration periods.
Appears in Collections:	[Graduate Institute of Civil Engineering] Electronic Thesis & Dissertation

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