自由液化场加速度反应数值试验
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摘要
场地液化除引起场地失稳和沉降外,也会对场地加速度反应产生重要作用。基于Finn模型实现自由场液化数值模拟试验,研究典型液化场加速度反应问题。研究结果表明:液化场加速度反应幅值与输入加速度幅值有关,液化场加速度放大倍数随输入地震动的增大而减小;液化场加速度反应大小与输入频率有很大关系,可液化场加速度反应的频率特征为:低频输入加速度反应幅值放大、高频输入反应幅值缩小,低频强化效应明显大于高频弱化效应;干砂弹性场也有低频放大高频滤波效应,但没有液化场显著;对于低频激振,若可液化场加速度经过放大且场地发生液化,场地加速度则衰减,若可液化场加速度经过放大但场地仍然未液化,场地加速度则维持稳态受迫振动状态;弹性场加速度反应从下到上逐渐增大,地表面放大最显著,液化场加速度放大在场地腰部最显著;高幅值输入易掩盖液化场加速度反应频率特性,低加速度幅值、低频输入下液化场的频率特性较明显。液化场地下结构抗震设计采用常规弹性场加速度反应系数,则会导致地下结构处于不安全状态。研究成果为液化场地下结构动力分析提供理论及试验基础。
Soil liquefaction would make ground failure and have effect on ground acceleration in addition.The liquefaction numerical simulation experiment of free field by the Finn model is realized;and the acceleration response question of liquefaction field has been studied.The study results indicate that:the liquefaction field acceleration response amplitude has relations with input acceleration amplitude,the acceleration magnification factor in liquefaction field decreases along with the increasing input seismic amplitude.The acceleration response essential feature of liquefaction field is low-frequency amplification,high-frequency reduction,the low-frequency amplification effect is higher than the high frequency reduction effect obviously.The dry sand elastic field also has the low-frequency amplification and high-frequency filter effect,but the effect of liquefaction field is more remarkable than that of elastic field.Regarding the low frequency excitation,if the liquefaction field acceleration enlarges,and the field have liquefied,then the field acceleration weakens.If the liquefaction field acceleration enlarged,but the field had still not liquefied,then the field acceleration maintained the stable forced oscillation condition.The elastic field acceleration response increased gradually from field bottom to top,the acceleration magnification in field surface is most remarkable,the acceleration magnification of liquefaction field is most remarkable in the field middle spot.The acceleration response frequency characteristic is not bright with high amplitude input,the liquefaction field acceleration response frequency characteristic is quite obvious with the low acceleration amplitude and low frequency input.If the acceleration magnification factor in conventional elastic field is used to anti-seismic design of underground structure,it will lead the underground structure to be unstable.Research results will provide a theoretical and experimental basis for the dynamic analysis of underground structures passing through liquefied soil layer.
Soil liquefaction would make ground failure and have effect on ground acceleration in addition.The liquefaction numerical simulation experiment of free field by the Finn model is realized;and the acceleration response question of liquefaction field has been studied.The study results indicate that:the liquefaction field acceleration response amplitude has relations with input acceleration amplitude,the acceleration magnification factor in liquefaction field decreases along with the increasing input seismic amplitude.The acceleration response essential feature of liquefaction field is low-frequency amplification,high-frequency reduction,the low-frequency amplification effect is higher than the high frequency reduction effect obviously.The dry sand elastic field also has the low-frequency amplification and high-frequency filter effect,but the effect of liquefaction field is more remarkable than that of elastic field.Regarding the low frequency excitation,if the liquefaction field acceleration enlarges,and the field have liquefied,then the field acceleration weakens.If the liquefaction field acceleration enlarged,but the field had still not liquefied,then the field acceleration maintained the stable forced oscillation condition.The elastic field acceleration response increased gradually from field bottom to top,the acceleration magnification in field surface is most remarkable,the acceleration magnification of liquefaction field is most remarkable in the field middle spot.The acceleration response frequency characteristic is not bright with high amplitude input,the liquefaction field acceleration response frequency characteristic is quite obvious with the low acceleration amplitude and low frequency input.If the acceleration magnification factor in conventional elastic field is used to anti-seismic design of underground structure,it will lead the underground structure to be unstable.Research results will provide a theoretical and experimental basis for the dynamic analysis of underground structures passing through liquefied soil layer.
引文
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[10]孙锐,袁晓铭,李雨润,等.循环荷载下液化对土层水平往返变形的影响[J].西北地震学报,2009,31(1):8–14.(SUN Rui,YUANXiaoming,LI Yurun,et al.Effect of liquefaction on cyclic deformationof soil layers under cyclic loads[J].Northwestern SeismologicalJournal,2009,31(1):8–14.(in Chinese))
[11]何剑平,陈卫忠.自由场典型液化特征数值模拟试验[J].地震工程与工程振动,2011,31(2):162–169.(HE Jianping,CHENWeizhong.Numerical simulation experiment of typical liquefactioncharacteristics for free field[J].Earthquake Engineering and EngineeringVibration,2011,31(2):162–169.(in Chinese))
[12]CLOUGH R W,PENZIEN J.结构动力学[M].北京:高等教育出版社,2006:17–29.(CLOUGH R W,PENZIEN J.Dynamics ofstructures[M].Beijing:Higher Education Press,2006:17–29.(in Chinese))
[2]吕西林,任红梅,李培振,等.液化场地自由场体系的数值分析及振动台试验验证[J].岩石力学与工程学报,2009,28(增2):4046–4 053.(LU Xilin,REN Hongmei,LI Peizhen,et al.Numerical analysisof free field system in liquefiable site and validation of shaking tabletests[J].Chinese Journal of Rock Mechanics and Engineering,2009,28(Supp.2):4 046–4 053.(in Chinese))
[3]孙锐,袁晓铭.场地液化对反应谱影响评价[J].应用基础与工程科学学报,2010,18(增1):173–180.(SUN Rui,YUAN Xiaoming.Evaluation of effect of site liquefaction on response spectrum[J].Journal of Basic Science and Engineering,2010,18(Supp.1):173–180.(in Chinese))
[4]MARTIN P P,SEED H B.One-dimensional dynamic ground responseanalyses[J].Journal of the Geotechnical Engineering Division,ASCE,1982,108(7):935–952
[5]陈国兴.岩土地震工程学[M].北京:科学出版社,2007:296–324.(CHEN Guoxing.Geotechnical earthquake engineering[M].Beijing:Science Press,2007:296–324.(in Chinese))
[6]MARTIN G R,FINN W D L,SEED H B.Fundamentals ofliquefaction under cyclic loading[J].Journal of the GeotechnicalEngineering Division,1975,101(5):423–438.
[7]SEED H B,SLIVER M L.Settlement of dry sands duringearthquakes[J].Journal of the Soil Mechanics and Foundation Division,ASCE,1972,98(4):381–397.
[8]BYRNE P M.A cyclic shear-volume coupling and pore pressuremodel for sand[C]//Proceedings of the 2nd International Conferenceon Recent Advances in Geotechnical Earthquake Engineering and SoilDynamics.Missouri,USA:[s.n.],1991:47–55.
[9]陈育民,徐鼎平.FLAC/FLAC3D基础与工程实例[M].北京:中国水利水电出版社,2009:296–324.(CHEN Yumin,XU Dingping.Foundation and project example of FLAC/FLAC3D[M].Beijing:ChinaWater Power Press,2009:296–324.(in Chinese))
[10]孙锐,袁晓铭,李雨润,等.循环荷载下液化对土层水平往返变形的影响[J].西北地震学报,2009,31(1):8–14.(SUN Rui,YUANXiaoming,LI Yurun,et al.Effect of liquefaction on cyclic deformationof soil layers under cyclic loads[J].Northwestern SeismologicalJournal,2009,31(1):8–14.(in Chinese))
[11]何剑平,陈卫忠.自由场典型液化特征数值模拟试验[J].地震工程与工程振动,2011,31(2):162–169.(HE Jianping,CHENWeizhong.Numerical simulation experiment of typical liquefactioncharacteristics for free field[J].Earthquake Engineering and EngineeringVibration,2011,31(2):162–169.(in Chinese))
[12]CLOUGH R W,PENZIEN J.结构动力学[M].北京:高等教育出版社,2006:17–29.(CLOUGH R W,PENZIEN J.Dynamics ofstructures[M].Beijing:Higher Education Press,2006:17–29.(in Chinese))
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