砂土中減振模型基樁之動態性質

歐韋麟(Wei-lin O)

指導教授 ： 張惠文

國立中央大學/工學院/土木工程學系/碩士(2007年)

摘要

交通運輸工具行經高架橋或橋樑時，可能引致振動，此振動經由橋墩傳遞至樁基，藉由基樁傳遞至承載層，再通過承載層傳遞至鄰近結構物或精密廠房之基礎，以致產生不良影響。本研究旨在探討上述振波之傳遞行為及降低此振波的方法。
為降低由基樁傳遞至承載層所產生之振波對鄰近結構物或精密廠房之振動影響，且考慮避免因減振過程造成基樁整體變位量過大，本研究於基樁上加裝兩不同減振器，分別為新型複合勁度減振彈簧與油壓彈簧阻尼器，進行一系列模型試驗。藉由模型試驗探討兩不同減振器加裝於基樁上時，對於樁尖在承載層中產生振波之減振成效、未改良樁與改良樁之樁周土壤中振波波傳衰減行為、衝擊加速度和彈簧勁度與減振器最大動態變位量之關係。
由試驗結果可知，樁身所承受之衝擊能量係藉由樁身傳遞至樁尖，再以樁尖為主要振源，向土層四周傳遞能量。而未改良樁與改良樁之樁周土壤中波傳衰減行為之衰減趨勢兩者十分相似，大約隨距樁尖距離越遠呈比例性的衰減消散。透過減振彈簧之作用，改良樁樁尖之振波能量至少衰減至未改良樁尖振波能量之40%以下，改良過的新型複合勁度彈簧減振器具有明顯的降低基樁整體的變位量之效果。

關鍵字

樁基礎 ； 位移量 ； 阻尼器 ； 減振彈簧 ； 地表振動

並列摘要

Transportation vehicles pass through viaduct or bridge may cause vibration. This vibration may transmit from pier to pile foundation, and then transmit to the bearing stratum. The wave propagation from the bearing stratum may cause damages to the adjacent structures or high-tech production facilities. This research investigated the transmission behaviors of waves mentioned above and the reducing method of this kind of vibration.

To reduce the vibration that may cause some detrimental effects to the residences, adjacent structures or high-tech production facilities, and considered to prevent too large displacement caused by vibration suppression, this research installed two different shock absorbing devices at the pile head. One is the new-type composite stiffness shock-absorbing spring and spring damping device with oil pressure. A series of model pile tests were carried out in the laboratory to investigate the effect of vibration mitigation in bearing stratum, behaviors of the attenuation of wave propagation around model pile in the soil and the relationships among dynamic displacement, impact acceleration and spring constant.

From the results of experiments, it was revealed that the impact energy is transferred from pile shaft to pile tip, and then transmit the energy to the surrounding soil layers from the pile tip. For the two kinds of model piles with shock-absorbing device set at pile head, the behaviors of attenuation of wave propagation approach are similar and attenuate gradually in proportion with distance. With the function of shock-absorbing spring, the vibration energy generated at the tip of the improved pile is at least 40%. It is also revealed that the new-type composite stiffness shock-absorbing spring can improve the problem of too large displacement caused by vibration suppression.

並列關鍵字

pile foundation ； displacement ； damper ； shock-absorbing spring ； vibration of ground surface

參考文獻

7.沈怡君、顏彬任、倪勝火，「高速鐵路引致地盤振動之地工防治對策探討」，地工技術雜誌，第八十八期，第15~22頁 (2001)。

18.曾乙哲，「複合勁度減振彈簧對砂土中模型樁動態性質之影響」，碩士論文，國立中央大學土木工程研究所，中壢 (2006)。

20.黃富雄，「原型填充槽溝對波傳阻隔效果之試驗研究」，碩士論文，國立成功大學土木工程研究所，台南 (2004)。

17.曾祥岳，「捷運列車引致振動之衰減模式之分析」，碩士論文，國立成功大學土木工程研究所，臺南 (2002)。

8.町田富士夫, Dynamic response of concrete railway bridges, Japan (2000)。