台灣公路與鐵路遍佈各地，為了保護鄰近區域之環境與行車安全，甚多區段採用橋樑結構，並由墩柱和基樁支撐，當車輛或是列車駛過橋梁時，對橋面版施加衝擊能量，此類能量透過橋墩傳遞至樁基礎，使基樁和周圍的土壤發生振動與沉陷。本研究嘗試設置減振器於基樁樁頭，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，降低基樁的沉陷量，而進行了一系列的室內模型試驗。以峴港砂填充於圓桶形土槽中模擬現地情況，並在砂土中央貫入模型樁，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，並於砂土層中之不同深度埋設加速度計量測樁周土壤振動，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。研究結果顯示，在樁頭加設減振器可獲得良好的改良效果，例如未改良模型樁受落錘衝擊時，樁身永久沉陷量為0.0610mm，採用液壓減振器，則基樁永久沉陷量可降至0.0135mm，且減振器之最大動態變位量只有0.0879mm，在規範的容許範圍之內，同時也有效降低模型樁各深度的振動量。 The nets of highway and railway are extending to everywhere in Taiwan. To protect the environment of the surrounding area or to keep the safety of transportation, many parts of these traffic constructions maybe designed as bridge which may be supported by pier and pile foundations. When vehicles or trains pass through these constructions, some impact or vibration loading will be caused. This kind of loading energy maybe transferred to the piers and the piles. This may cause vibration of the surrounding soil layer or settlement of the pile foundation. 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, the Danang sand was 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 imbedded depth of model pile. And the permanent settlement of pile shaft and dynamic displacement of shock absorber were measured with two sets of LVDT. The experimental results showed that an excellent improvement effect is obtained by setting a shock absorber on pile head. For instance, the permanent settlement of model pile improved with shock absorber is reduced to 0.0135mm, while the value of the untreated model pile is 0.061mm. Moreover, the maximum dynamic displacement of shock absorber is 0.0879mm which is smaller than the value limited by the design code. It is also observed that the vibrations at various depths of soil are reduced effectively.
