地震动持时压缩比对可液化地基地震反应影响的振动台试验
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摘要
在与可液化场地相关的振动台模型试验中,地震动持时按照时间相似比压缩后,所输入地震动的持时、频率、能量等特性均发生改变,这将对液化地基在地震荷载下的动力响应产生显著影响。以持时压缩比例为研究的唯一变量,依托小型振动台试验,分析了各组试验中可液化地基土在地震中的宏观现象、加速度反应、孔压比发展等,针对与可液化场地相关振动台试验设计中的地震动持时按照时间相似比压缩后对液化场地动力响应影响的问题进行研究。试验结果表明:地震动记录按照很小的相似比压缩后持时太短,地震动峰值一定时,可液化场地则有可能不发生液化;地震动持时越长,地震动能量越大,超孔隙水压力随地震动的输入积累迅速,场地土液化现象越明显,土体中加速度反应也表现出不同规律。根据得到的试验结果,建议在涉及可液化场地的振动台模型试验中,所输入的地震记录采用原始持时地震动记录或按照较大时间相似比压缩的地震动记录。
In the shaking table model test on liquefiable sandy soil, the duration, frequency, energy and other characteristics of ground motion have changed after the seismic record time is compressed according to the time similarity ratio, and it will have a significant impact on the dynamic response of liquefiable foundation under seismic loading. The time compression ratio is the only variable in this series of shaking table model tests, and the effects are analysed by the characteristics, such as macroscopic phenomena, acceleration, pore water pressure. The effect of dynamic response of liquefied site in the shaking table tests with seismic record after time holding compression is researched in this paper. Results show that when the PGA of the input ground motion is similar, liquefied site may not be liquefied if the seismic record time is compressed. The longer the duration, and the greater the energy of the ground motion, excess pore water pressure accumulates rapidly, and the phenomenon of soil liquefaction and the filter isolation effects are obvious. According to the results of the tests, it is suggested that the original ground motion could be directly adopted by the shaking table tests regarding liquefaction as research objective.
In the shaking table model test on liquefiable sandy soil, the duration, frequency, energy and other characteristics of ground motion have changed after the seismic record time is compressed according to the time similarity ratio, and it will have a significant impact on the dynamic response of liquefiable foundation under seismic loading. The time compression ratio is the only variable in this series of shaking table model tests, and the effects are analysed by the characteristics, such as macroscopic phenomena, acceleration, pore water pressure. The effect of dynamic response of liquefied site in the shaking table tests with seismic record after time holding compression is researched in this paper. Results show that when the PGA of the input ground motion is similar, liquefied site may not be liquefied if the seismic record time is compressed. The longer the duration, and the greater the energy of the ground motion, excess pore water pressure accumulates rapidly, and the phenomenon of soil liquefaction and the filter isolation effects are obvious. According to the results of the tests, it is suggested that the original ground motion could be directly adopted by the shaking table tests regarding liquefaction as research objective.
引文
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[12]杜修力,李霞,陈国兴,等.悬挂式层状多向剪切模型箱的设计分析及试验验证[J].岩土工程学报,2012,34(3):424-432.DU Xiu-li,LI Xia,CHEN Guo-xing,et al.Design and test verification of suspension multidirectional laminar shear box[J].Chinese of Geotechnical Engineering,2012,34(3):424-432.
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[14]ARIAS A.A measure of earthquake intensity,in seismic design for nuclear power plants[R].Cambridge:MITPress,1970.
[2]IAI S.Similitude for shaking table tests on soil-structure-fluid model in 1g gravitational field[J].Soils and Foundations,1989,29(1):105-118.
[3]IAI S,TOBITA T,NAKAHARA T.Generalised scaling relations for dynamic centrifuge tests[J].Geotechnique,2005,55(5):355-362.
[4]HWANG J I.Behavior of piles subjected to flow of liquefied soil and verification of similitude law for 1g shaking table tests[D].Seoul:Seoul National University,2004.
[5]RAMON V.Comparing liquefaction phenomena observed during the 2010 Maule,Chile earthquake and 2011 Great East Japan[C]//Proceedings of the International Symposium on Engineering Lessons Learned from the2011 Great East Japan Earthquake.Tokyo:[s.n.],2010:707-718.
[6]李振宝,李晓亮,唐贞云,等.土-结构动力相互作用的振动台试验研究综述[J].震灾防御技术,2010,5(4):439-450.LI Zhen-bao,LI Xiao-liang,TANG Zhen-yun,et al.Review of shaking table test of soil structure dynamic interaction[J].Technology for Earthquake Disaster Prevention,2010,5(4):439-450.
[7]HIROKO S,KOHJI T,MASAYOSHI S,et al.Factor affecting horizontal subgrade reaction of piles during soil liquefaction and lateral spreading[C]//Seismic Performance and Simulation of Pile Foundations,ASCE.Davis:[s.n.],2006:1-10.
[8]TSUKAMOTO Y,ISHIHARA K,SAWADA S,et al.Settlement of rigid circular foundations during seismic shaking in shaking table tests[J].International Journal of Geomechanics,2012,12(4):462-470.
[9]CHEN C H,UENG T S.Behavior of model piles in a liquefiable soil in shaking table tests[C]//Proceedings of the 10th National Conference on Earthquake Engineering.Anchorage:[s.n.],2014.
[10]唐亮,凌贤长,徐鹏举,等.可液化场地高承台群桩-土-桥梁结构地震相互作用振动台试验[J].中国公路学报,2010,23(4):51-57.TANG Liang,LING Xian-chang,XU Peng-ju,et al.Shaking table test for seismic interaction of pile groups-soil-bridge structure with elevated cap in liquefiable ground[J].China Journal of Highway and Transport,2010,23(4):51-57.
[11]唐亮,凌贤长,徐鹏举,等.可液化场地桥梁群桩-独柱墩结构地震反应振动台试验研究[J].土木工程学报,2009,42(11):102-107.TANG Liang,LING Xian-chang,XU Peng-ju,et al.Shaking table tests for seismic response of pile-supported bridge structure with single-column pier in liquefiable ground[J].China Civil Engineering Journal,2009,42(11):102-107.
[12]杜修力,李霞,陈国兴,等.悬挂式层状多向剪切模型箱的设计分析及试验验证[J].岩土工程学报,2012,34(3):424-432.DU Xiu-li,LI Xia,CHEN Guo-xing,et al.Design and test verification of suspension multidirectional laminar shear box[J].Chinese of Geotechnical Engineering,2012,34(3):424-432.
[13]陈国兴,王志华,左熹,等.振动台试验叠层剪切型土箱的研制[J].岩土工程学报,2010,32(1):89-97.CHEN Guo-xing,WANG Zhi-hua,ZUO Xi,et al.Development of laminar shear soil container for shaking table tests[J].Chinese Journal of Geotechnical Engineering,2010,32(1):89-97.
[14]ARIAS A.A measure of earthquake intensity,in seismic design for nuclear power plants[R].Cambridge:MITPress,1970.