可液化场地桥梁群桩基础地震响应振动台试验研究
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摘要
针对上覆黏土层、下部饱和砂层结构的可液化场地条件,采用2×2低承台群桩—独柱墩结构,完成了可液化场地群桩–土–桥梁结构地震相互作用振动台试验。试验表明:在小幅震动阶段孔压仅有少量积累,孔压积累主要发生在强烈振动段;孔压随震动幅值增大、持时延长而变得更高;最强烈液化作用滞后于峰值加速度时刻。砂层加速度反应受场地液化影响较大;随着砂层液化的发展,土层位移峰值时刻与输入地震波峰值时刻、土层加速度峰值时刻之间表现出明显的时滞特征,而土层位移对桩的弯矩反应起着越来越明显的作用,且液化砂层位移对桩土相互作用力影响效应已凸显;完全液化砂层的承载力并未全部丧失;无论砂层液化与否,桩与砂层加速度反应规律保持一致;地震中土层分界附近桩的加速度、弯矩出现突变。振动台试验无疑为可液化场地桥梁群桩抗震性能研究提供必要铺垫。
Shaking table test on seismic low-cap pile groups-soil-bridge structure interaction in liquefiable ground with the overlying clay layer and the lower saturated sand layer is completed.The test indicates that pore pressure caused by the slight vibration during earthquake is only a small amount of accumulation,and pore pressure accumulation mainly occurs at the stage of strong vibration.The pore pressure gradually increases as the input motion amplitude becomes larger and the shaking duration becomes longer.It’s obtained that the strongest liquefaction lags behind the peak acceleration time.Acceleration of the sand is remarkably influenced by soil liquefaction.With the development of soil liquefaction,the time-delay characteristics between the peak soil displacement time and the peak input motion time,and the peak acceleration time of soil are significantly displayed,and soil displacement plays an increasingly prominent role in the bending moment of the pile.Similarly,the displacement of liquefied sand has a specially obvious effect on pile-soil interaction.The fully liquefied sand doesn’t completely lose the bearing capacity.Whether the sand is liquefied or not,the acceleration law of the pile and the sand maintains consistent.During the earthquake,the jump reaction of the acceleration and the bending moment on the pile is observed near the soil interface.It’s no doubt that the shaking table test provides the necessary groundwork to study seismic performance of pile groups of bridges.
Shaking table test on seismic low-cap pile groups-soil-bridge structure interaction in liquefiable ground with the overlying clay layer and the lower saturated sand layer is completed.The test indicates that pore pressure caused by the slight vibration during earthquake is only a small amount of accumulation,and pore pressure accumulation mainly occurs at the stage of strong vibration.The pore pressure gradually increases as the input motion amplitude becomes larger and the shaking duration becomes longer.It’s obtained that the strongest liquefaction lags behind the peak acceleration time.Acceleration of the sand is remarkably influenced by soil liquefaction.With the development of soil liquefaction,the time-delay characteristics between the peak soil displacement time and the peak input motion time,and the peak acceleration time of soil are significantly displayed,and soil displacement plays an increasingly prominent role in the bending moment of the pile.Similarly,the displacement of liquefied sand has a specially obvious effect on pile-soil interaction.The fully liquefied sand doesn’t completely lose the bearing capacity.Whether the sand is liquefied or not,the acceleration law of the pile and the sand maintains consistent.During the earthquake,the jump reaction of the acceleration and the bending moment on the pile is observed near the soil interface.It’s no doubt that the shaking table test provides the necessary groundwork to study seismic performance of pile groups of bridges.
引文
[1]FINN W D L,FUJITA N.Piles in liquefiable soils:seismic analysis and design issues[J].Soil Dynamics and Earthquake Engineering,2002,22:731–742.
[2]刘惠珊,乔太平.可液化土中桩基设计计算方法的探讨[J].工业建筑,1983(4):19–24.(LIU Hui-shan,QIAO Tai-ping.Discussion of computation method on piles design in liquefied soil[J].Industrial Construction,1983(4):19–24.(in Chinese))
[3]WILSON D W.Soil–pile–superstructure interaction in liquefying and soft clay[D].California:University of California,1998.
[4]李雨润,袁晓铭.液化场地上土体侧向变形对桩基影响研究评述[J].世界地震工程,2004,20(2):17–22.(LI Yu-run,YUAN Xiao-ming.State-of-art of study on influences of liquefaction-induced soil spreading over pile foundation response[J].World Earthquake Engineering,2004,20(2):17–22.(in Chinese))
[5]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 Jian-min.Effect of large horizontal post-liquefaction deformation of level ground on pile foundation[J].Journal of Building Structures,2001,22(5):75–78.(in Chinese))
[6]王建华,冯士伦.液化土层中桩基水平承载特性分析[J].岩土力学,2005,26(10):1597–1601.(WANG Jian-hua,FENG Shi-lun.Research on lateral resistance of pile foundation in liquefaction strata[J].Rock and Soil Mechanics,2005,26(10):1597–1601.(in Chinese))
[7]凌贤长,王东升.液化场地桩–土–桥梁结构动力相互作用振动台试验研究进展[J].地震工程与工程振动,2002,22(4):51–59.(LING Xian-zhang,WANG Dong-sheng.Study on shaking table test for seismic interaction of pile-soil-bridge structure in case of soil liquefaction caused by earthquake[J].Earthquake Engineering and Engineering Vibration,2002,22(4):51–59.(in Chinese))
[8]KAGAWA T,MINOWA C,MIZUNO H,et al.Shaking table testing on piles in liquefying sand[C]//Proc of 5th US National Conf on Earthq Eng,Chicago,1994:107–116.
[9]TAMURA S,SUZUKI Y,TSUCHIYA T,et al.Dynamic response and failure mechanisms of a pile foundation during soil liquefaction by shaking table test with a large-scale laminar shear box(CD ROM paper No 0903)[C]//12WCEE.New Zealand,2000.
[10]范立础.桥梁抗震[M].上海:同济大学出版社,1997.(FAN Li-chu.Seismic design of highway bridges[M].Shanghai:Tongji University Press,1997.(in Chinese))
[11]凌贤长,王东升,王志强,等.液化场地桩–土–桥梁结构动力相互作用大型振动台模型试验研究[J].土木工程学报,2004,37(11):67–72.(LING Xian-zhang,WANG Dong-sheng,WANG Zhi-qiang,et al.Large-scale shaking table model test of dynamic soil-pile-bridge structure interaction in ground of liquefaction[J].China Civil Engineering Journal,2004,37(11):67–72.(in Chinese))
[12]凌贤长,王臣,王成,等.液化场地桩–土–桥梁结构动力相互作用振动台试验模型相似设计方法[J].岩石力学与工程学报,2004,23(3):450–456.(LING Xian-zhang,WANG Chen,WANG Cheng.Scale modeling method of shaking table test of dynamic interaction of pile-soil-bridge structure in ground of soil liquefaction[J].Chinese Journal of Rock Mechanics and Engineering,2004,23(3):450–456.(in Chinese))
[13]伍小平,孙利民,胡世德,等.振动台试验用层状剪切变形土箱的研制[J].同济大学学报,2002,30(7):781–785.(WU Xiao-ping,SUN Li-min,HU Shi-de,et al.Development of laminar shear box used in shaking table test[J].Journal of Tongji University,2002,30(7):781–785.(in Chinese))
[14]吕西林,陈跃庆,陈波.结构–地基动力相互作用体系振动台模拟试验研究[J].地震工程与工程振动,2000,20(4):20–29.(LüXi-lin,CHEN Yue-qing,CHEN Bo,et al.Shaking table testing of dynamic soil-structure interaction system[J].Earthquake Engineering and Engineering Vibration,2000,20(4):20–29.(in Chinese))
[2]刘惠珊,乔太平.可液化土中桩基设计计算方法的探讨[J].工业建筑,1983(4):19–24.(LIU Hui-shan,QIAO Tai-ping.Discussion of computation method on piles design in liquefied soil[J].Industrial Construction,1983(4):19–24.(in Chinese))
[3]WILSON D W.Soil–pile–superstructure interaction in liquefying and soft clay[D].California:University of California,1998.
[4]李雨润,袁晓铭.液化场地上土体侧向变形对桩基影响研究评述[J].世界地震工程,2004,20(2):17–22.(LI Yu-run,YUAN Xiao-ming.State-of-art of study on influences of liquefaction-induced soil spreading over pile foundation response[J].World Earthquake Engineering,2004,20(2):17–22.(in Chinese))
[5]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 Jian-min.Effect of large horizontal post-liquefaction deformation of level ground on pile foundation[J].Journal of Building Structures,2001,22(5):75–78.(in Chinese))
[6]王建华,冯士伦.液化土层中桩基水平承载特性分析[J].岩土力学,2005,26(10):1597–1601.(WANG Jian-hua,FENG Shi-lun.Research on lateral resistance of pile foundation in liquefaction strata[J].Rock and Soil Mechanics,2005,26(10):1597–1601.(in Chinese))
[7]凌贤长,王东升.液化场地桩–土–桥梁结构动力相互作用振动台试验研究进展[J].地震工程与工程振动,2002,22(4):51–59.(LING Xian-zhang,WANG Dong-sheng.Study on shaking table test for seismic interaction of pile-soil-bridge structure in case of soil liquefaction caused by earthquake[J].Earthquake Engineering and Engineering Vibration,2002,22(4):51–59.(in Chinese))
[8]KAGAWA T,MINOWA C,MIZUNO H,et al.Shaking table testing on piles in liquefying sand[C]//Proc of 5th US National Conf on Earthq Eng,Chicago,1994:107–116.
[9]TAMURA S,SUZUKI Y,TSUCHIYA T,et al.Dynamic response and failure mechanisms of a pile foundation during soil liquefaction by shaking table test with a large-scale laminar shear box(CD ROM paper No 0903)[C]//12WCEE.New Zealand,2000.
[10]范立础.桥梁抗震[M].上海:同济大学出版社,1997.(FAN Li-chu.Seismic design of highway bridges[M].Shanghai:Tongji University Press,1997.(in Chinese))
[11]凌贤长,王东升,王志强,等.液化场地桩–土–桥梁结构动力相互作用大型振动台模型试验研究[J].土木工程学报,2004,37(11):67–72.(LING Xian-zhang,WANG Dong-sheng,WANG Zhi-qiang,et al.Large-scale shaking table model test of dynamic soil-pile-bridge structure interaction in ground of liquefaction[J].China Civil Engineering Journal,2004,37(11):67–72.(in Chinese))
[12]凌贤长,王臣,王成,等.液化场地桩–土–桥梁结构动力相互作用振动台试验模型相似设计方法[J].岩石力学与工程学报,2004,23(3):450–456.(LING Xian-zhang,WANG Chen,WANG Cheng.Scale modeling method of shaking table test of dynamic interaction of pile-soil-bridge structure in ground of soil liquefaction[J].Chinese Journal of Rock Mechanics and Engineering,2004,23(3):450–456.(in Chinese))
[13]伍小平,孙利民,胡世德,等.振动台试验用层状剪切变形土箱的研制[J].同济大学学报,2002,30(7):781–785.(WU Xiao-ping,SUN Li-min,HU Shi-de,et al.Development of laminar shear box used in shaking table test[J].Journal of Tongji University,2002,30(7):781–785.(in Chinese))
[14]吕西林,陈跃庆,陈波.结构–地基动力相互作用体系振动台模拟试验研究[J].地震工程与工程振动,2000,20(4):20–29.(LüXi-lin,CHEN Yue-qing,CHEN Bo,et al.Shaking table testing of dynamic soil-structure interaction system[J].Earthquake Engineering and Engineering Vibration,2000,20(4):20–29.(in Chinese))
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