基樁減振器幾何尺寸變化之減振變形特性

吳建宏(Chien-hung Wu)

指導教授 ： 張惠文

國立中央大學/工學院/土木工程學系/碩士(2015年)

摘要

本研究嘗試設置液壓減振器於基樁樁頭，改變基樁承載瞬間載重之機制，讓基樁承受瞬間載重的衝擊減少，降低基樁的永久沉陷量，而進行了一系列的室內模型試驗。以峴港砂與礫石填充於圓桶形土槽中模擬現地情況，並在砂土中央放置模型樁至承載層，用不同高度的落錘衝擊樁頭，模擬車輛或是列車的瞬間衝擊力與靜載重，並於砂土層與礫石層中之不同深度埋設加速度計，以量測樁周土壤之振動，設置兩支LVDT量測樁身永久沉陷量和減振器上部的動態變位量。由前人的研究可知液壓減振器具有良好的最大動態變位量不大，及基樁之靜載重大小會影響其極限支承力，為了在最大動態位移量可接受的範圍內求得較好的減振效果，故控制其體積大小，本研究改變液壓減振器之幾何尺寸，探討減振與變形的關係，並進行一系列的模型試驗。由試驗結果得知，當減振器之直徑加大，其土壤振動與基樁永久沉陷量皆會減小，而當減振器高度增加時，僅能夠減小其基樁永久沉陷量，減振效果卻未見增大，故加大減振器之直徑為一較好的改良方法。

關鍵字

模型樁 ； 液壓減振器 ； 加速度 ； 動態變位量 ； 永久沉陷量

並列摘要

This research tried to set a shock absorber on pile head to improve the transfer mechanism of shock loading, and expect to reduce the vibration on soil and settlement of pile foundation. A series of model pile tests were performed in laboratory. In these tests, Danang sand and gravel were filled in a cylindrical test pit to simulate sand layer and a steel pipe was set at the center of this test pit as model pile. Drop a steel hammer with various heights on the head of model pile to simulate the shock or loading of passing vehicle or train. The acceleration data was measured with accelerometers set at various depth. And the permanent settlement of pile shaft and dynamic displacement of shock absorber were measured with two sets of LVDT. According to the previous studies, it is understood that the dynamic displacement of hydraulic shock-absorber is not apparent and the static load on pile will influence the value of ultimate load. In order to obtain the best damping effect within the acceptable dynamic displacement, this research changed the diameter and height of shock absorber to perform a series of experiments. The experimental results showed that a shock absorber with larger diameter will achieve a better result of vibration suppression and smaller permanent settlement. The a shock absorber with larger height can reduce the maximum amount of permanent settlement, but has no effect to vibration suppression.

並列關鍵字

model pile ； hydraulic shock-absorber ； acceleration ； dynamic displacement ； permanent settlement

參考文獻

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