侧向流动地基单桩基础离心机振动台试验研究
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摘要
该文在清华大学土工离心机振动台上开展了倾斜可液化地基中刚性单桩基础的试验研究,观测了地基的加速度、位移、孔压和桩基础的弯矩等响应。研究结果显示:地震中地基浅层部分较快达到液化状态,不同深度超静孔隙水压力的累积与消散并不相同;砂土的液化使得地基的加速度响应发生变化,有效地过滤了地震波的部分高频段;地震过程中桩身弯矩峰值出现在浅层地基达到初始液化后,且最大弯矩出现在桩头;倾斜地基使得桩身产生了较大的残余弯矩。由此表明在侧向流动地基中,液化前、液化后大变形和地震后永久位移三个不同阶段桩的受力并不相同。在进行可液化地基中桩基础的研究中,应考虑这三个不同阶段桩基础的受力要求。该研究加深了对倾斜液化地基中桩基础的地震响应的理解,有助于进一步的揭示地震过程中可液化地基桩基础的震损机理。
Dynamic centrifuge model tests on single pile foundation in sloping liquefiable ground were conducted to investigate the behavior of pile foundations in liquefiable soil during earthquakes.Acceleration and excess pore pressure of the foundation and moment of the pile were measured and recorded during the test.Test results showed the top of the ground liquefied and excess pore pressure patterns varied with the depth.Upon liquefaction,soil filtered out high frequency contents of the earthquake,reducing the maximum acceleration of the earthquake.The maximum moment of the pile occurred after initial liquefaction at the pile head.Relatively large residual moment was observed in the pile after the excitation.These results indicate that the response of piles varies in the three different stages including pre-liquefaction,post-liquefaction and lateral ground displacement after earthquakes,and further studies should consider these differences.This research enhanced the understanding of pile responses during earthquake,and would provide basis for further investigation into the soil-pile-structure interaction mechanism in liquefiable soil.
Dynamic centrifuge model tests on single pile foundation in sloping liquefiable ground were conducted to investigate the behavior of pile foundations in liquefiable soil during earthquakes.Acceleration and excess pore pressure of the foundation and moment of the pile were measured and recorded during the test.Test results showed the top of the ground liquefied and excess pore pressure patterns varied with the depth.Upon liquefaction,soil filtered out high frequency contents of the earthquake,reducing the maximum acceleration of the earthquake.The maximum moment of the pile occurred after initial liquefaction at the pile head.Relatively large residual moment was observed in the pile after the excitation.These results indicate that the response of piles varies in the three different stages including pre-liquefaction,post-liquefaction and lateral ground displacement after earthquakes,and further studies should consider these differences.This research enhanced the understanding of pile responses during earthquake,and would provide basis for further investigation into the soil-pile-structure interaction mechanism in liquefiable soil.
引文
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[14]Zeng X,Wu J,Young B A.Influence of viscous fluidson properties of sand[J].Geotechnical Testing Journal,1998,21(1):45―51.
[15]李培振,任红梅,吕西林,程磊.液化地基自由场振动台模型试验研究[J].地震工程与工程振动,2008,28(2):171―178.Li Peizhen,Ren Hongmei,Lv Xilin,Cheng Lei.Shakingtable test on free field considering soil liquefaction[J].Journal of Earthquake Engineering and EngineeringVibration,2008,28(2):171―178.(in Chinese)
[16]王睿,张建民,张嘎.离心机振动台试验中地基侧向流动位移分析方法研究[J].世界地震工程,2010,26(增刊):225―229.Wang Rui,Zhang Jianmin,Zhang Ga.Lateral spreadingground displacement analysis method in centrifugeshaking table tests[J].World Earthquake Engineering,2010,26(Suppl):225―229.(in Chinese)
[17]张建民.水平地基液化后大变形对桩基础的影响[J].建筑结构学报,2001,22(5):75―78.Zhang Jianmin.Influence of large deformation inhorizontal ground on pile foundations[J].Journal ofBuilding Structures,2001,22(5):75―78.(in Chinese)
[2]Hamada M.Large ground deformations and their effectson lifelines:1964 Niigata Earthquake.Case Studies ofLiquefaction and Lifelines Performance during PastEarthquake[R].Buffalo,NY,USA:National Centre forEarthquake Engineering Research,1992.
[3]Yoshida N,Watanabe H,Yasuda S.Liquefaction-induced ground failure and related damageto structures during 1991 Telire-Limon,Costa Rica,earthquake[C].Hawaii:NCEER,1992.
[4]Tokimatsu K.Behaviour and design of pile foundationssubjected to earthquakes[C].Singapore:WorldScientific,2003.
[5]Hamada M,Wakamatsu K.Liquefaction,grounddeformaion and their related damage to structures[R].Tokyo,Japan:Committee of Earthquake Engineering,Japan Society of Civil Engineers,1996.
[6]Ashford S A,Juirnarongrit T.Performance of lifelinessubjected to lateral spreading[R].San Diego,USA:Pacific Earthquake Engineering Research Center,2006.
[7]苏栋,李相菘.可液化土中单桩地震响应的离心机试验研究[J].岩土工程学报,2006,28(4):423―427.Su Dong,Li Xiangsong.Centrifuge investigation onseismic response of single pile in liquefiable soil[J].Chinese Journal of Geotechnical Engineering,2006,28(4):423―427.(in Chinese)
[8]Berrill J,Yasuda S.Liquefaction and piled foundations:Some issues[J].Journal of Earthquake Engineering,2002,6(Suppl 1):1―41.
[9]Yoshida N,Tazoh T,Wakamatsu K,Yasuda S,TowhataI,Nakazawa H,Kiku H.Causes of Showa bridgecollapse in the 1964 Niigata earthquake based oneyewitness testimony[J].Soils and Foundations,2007,47(6):1075―1087.
[10]Bhattacharya S,Madabhushi S P G,Bolton M D.Analternative mechanism of pile failure in liquefiabledeposits during earthquakes[J].Geotechnique,2005,55(3):259―263.
[11]张建民,于玉贞,濮家骝,殷昆亭,黄生月,张秀英.电液伺服控制离心机振动台系统研制[J].岩土工程学报,2004,26(6):843―845.Zhang Jianmin,Yu Yuzhen,Pu Jialiu,Yin Kunting,Huang Shengyue,Zhang Xiuying.Development of ashaking table in electro-hydraulic servo-controlcentrifuge[J].Chinese Journal of GeotechnicalEngineering,2004,26(6):843―845.(in Chinese)
[12]刘晶波,刘祥庆,王宗纲,王文晖.砂土地基自由场离心机振动台模型试验[J].清华大学学报(自然科学版),2009,49(9):1463―1466.Liu Jingbo,Liu Xiangqing,Wang Zonggang,WangWenhui.Dynamic centrifuge model test of an unconfinedsandy foundation[J].Journal of Tsinghua University(Science&Technology),2009,49(9):1463―1466.(in Chinese)
[13]周景星,李广信,虞石民,王洪瑾.基础工程[M].第2版.北京:清华大学出版社,2007:16―17.Zhou Jingxing,Li Guangxin,Yu Shimin,Wang Hongjin.Foundation engineering[M].2nd ed.Beijing:TsinghuaUniversity Press,2007:16―17.(in Chinese)
[14]Zeng X,Wu J,Young B A.Influence of viscous fluidson properties of sand[J].Geotechnical Testing Journal,1998,21(1):45―51.
[15]李培振,任红梅,吕西林,程磊.液化地基自由场振动台模型试验研究[J].地震工程与工程振动,2008,28(2):171―178.Li Peizhen,Ren Hongmei,Lv Xilin,Cheng Lei.Shakingtable test on free field considering soil liquefaction[J].Journal of Earthquake Engineering and EngineeringVibration,2008,28(2):171―178.(in Chinese)
[16]王睿,张建民,张嘎.离心机振动台试验中地基侧向流动位移分析方法研究[J].世界地震工程,2010,26(增刊):225―229.Wang Rui,Zhang Jianmin,Zhang Ga.Lateral spreadingground displacement analysis method in centrifugeshaking table tests[J].World Earthquake Engineering,2010,26(Suppl):225―229.(in Chinese)
[17]张建民.水平地基液化后大变形对桩基础的影响[J].建筑结构学报,2001,22(5):75―78.Zhang Jianmin.Influence of large deformation inhorizontal ground on pile foundations[J].Journal ofBuilding Structures,2001,22(5):75―78.(in Chinese)
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