通隧引致隧道上方短樁之反應; Short pile responses caused by tunneling

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Title:	通隧引致隧道上方短樁之反應;Short pile responses caused by tunneling
Authors:	黃信富;Hsin-Fu Huang
Contributors:	土木工程研究所
Keywords:	樁載重試驗;砂土;土壤漏失;隧道;基樁;Pile loading test;Sandy ground;Ground loss;Pile;Tunnel
Date:	2006-12-15
Issue Date:	2009-09-18 17:20:18 (UTC+8)
Publisher:	國立中央大學圖書館
Abstract:	本研究利用離心模型試驗，探討於飽和砂土層中進行隧道掘進導致之地盤變位對隧道上方既存基樁之影響。以體積控制方式模擬土壤漏失量，分別探討（1）於固定土壤漏失量且改變基樁距隧道中心不同距離以及於隧道中心軸正上方，在不同土壤漏失量下，進行基樁載重試驗，以觀察地中應力場改變時基樁承載力的變化。（2）於鄰旁隧道以不同工作載重比且改變基樁距隧道中心不同距離，觀察通隧引致既存基樁之反應。研究結果顯示，於新挖隧道正上方進行基樁載重試驗，在土壤漏失量為2%的時候，基樁承載力減少60%，其樁尖承載力減少95%。通隧引致鄰近基樁之荷重傳遞行為，會受到下列因素影響：（1）通隧引致隧道之土壤漏失量，（2）基樁距隧道中心軸之水平距離，（3）樁頭所含工作載重的大小。通隧引致隧道之土壤漏失量大小會影響樁身軸向力、樁身表皮摩擦力與樁頭沉陷量。當土壤漏失量開始產生時，樁身軸向力會因為樁尖點承力減小而隨著減少，使得樁身表面摩擦力逐漸發揮作用。隨著土壤漏失量增加，樁頭沉陷量也會逐漸增加。基樁距隧道中心軸之水平距離逐漸拉大，則樁身軸向力分布、樁身表面摩擦力的變化量與樁頭沉陷量會逐漸變小，當基樁距隧道中心軸之距離為10m時，則基樁受到的影響不大。於隧道中心軸正上方，在樁頂加載為工作載重比0.5時，樁尖與樁周的土壤會提供較大的阻抗，則土壤漏失量產生時該樁身表面摩擦力為正摩擦力，於樁頂加載為工作載重比0.3，則土壤漏失量產生時樁身表面摩擦力為負摩擦力。 A series of centrifuge model tests were performed to assess tunneling-induced ground deformations in sandy ground and their effects on adjacent pile foundations. Two topics have been investigated by modeling the ground loss with the way of volume control in this study. First of all, the pile loading test has been analyzed in the different conditions, including the ground loss and the distance between the pile and the tunnel center. Secondly, the load transfer mechanism of the piles has been analyzed in the different conditions, including ground losses, the load on the pile head, and the distance between the pile and the tunnel center. According to the result in the research, the loss of the ultimate bearing capacity and of the pile end bearing capacity were 60% and 95%, respectively. When the ground loss reached 2% during the pile loading test conducted above the tunnel center. Load transfer behaviors on a pile caused by adjacent tunneling mainly depended on the followed factors: (1) ground loss, (2) the horizontal distance between the pile and the tunnel center, (3)the axial load of the pile head. Ground loss caused by tunneling would affect the distribution of axial force, the skin friction on a pile, and the settlement of pile head. The distribution of axial force along a pile will decrease with decreasing pile point bearing capacity if the ground loss increased. The settlement of pile head will also increase with increasing the ground loss. The increase in the horizontal distance between the pile and the tunnel center will lead to the decrease in the settlement of pile head and the axial force and the skin friction on a pile. The tunneling will not affect the pile if the horizontal distance between the pile and the tunnel center was larger than 10m. When the working load ratio on pile head was 0.5, the soil around the pile will provide the resistance for the pile, and the skin friction along a pile was positive as ground loss occurred; however, that was negative under the condition of 0.3 of working load ratio on the pile.
Appears in Collections:	[Graduate Institute of Civil Engineering] Electronic Thesis & Dissertation

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