桩板式抗滑挡墙地震响应的振动台试验研究
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摘要
汶川地震路基震害调查表明,在顺层或堆积体边坡中的桩板式抗滑挡墙具有良好的抗震性能。为了更好地了解该结构的抗震性能和优化抗震设计方法,以大型振动台模型试验为手段对其进行研究。为明确地震作用下桩板式抗滑挡墙的地震响应特性,试验采用缩尺的卧龙台站实测地震波对模型激励。试验结果揭示了土压力沿桩身分布规律、桩体位移和边坡岩土体加速度的地震响应特征。研究表明,地震土压力沿桩身呈非线性分布,竖向地震荷载对水平加速度有放大效果。所以,双向加载时的地震土压力比水平单向加载时大,但二者差距在地震基本烈度Ⅶ、Ⅷ度区域不显著。滑坡推力、滑床对桩的土体抗力和桩身位移均与输入地震动峰值加速度成正比,即随着地震动峰值加速度的增加,加速度放大比增大;滑动面材料剪切强度折减,滑坡推力、土体抗力和抗身位移均增大,且增大速率加快。此外,结合试验成果,建议了桩板式抗滑挡墙设计时地震综合影响系数Cz的合理取值,对应地震基本烈度Ⅶ、Ⅷ、Ⅸ度区分别为0.2、0.35、0.4。试验结果有助于揭示该结构抗震机制,也为其抗震设计提供了可靠依据。
From the investigation of seismic hazards of subgrade in Wenchuan earthquake,the anti-sliding sheet pile wall has been proven to be an excellent seismic structure in bedding or accumulation slopes.In order to understand the seismic performance better and optimize the seismic design,large shaking table test is performed.In order to ascertain the seismic response characteristics of anti-sliding sheet pile wall,acceleration histories recorded at Wolong station in Wenchuan earthquake are scaled and used to excite the model.The test results reveal the distribution pattern of earth pressure along the pile,seismic response of displacement and accelerations in slopes under ground shaking.The research demonstrates that the distribution of seismic earth pressure is nonlinear along the pile;and vertical seismic load has amplification effect on horizontal acceleration.Therefore,the seismic earth pressure under bidirectional loads is larger than that under unidirectional horizontal load.However,the difference between them is not obvious in seismic zones of basic intensity Ⅶ and Ⅷ.Furthermore,landslide thrust,soil resistance of sliding bed,and displacement of pile are proportional to the input seismic peak acceleration.It means that,with the increase of input peak seismic acceleration,the amplification ratio of acceleration increases and the material shear strength of sliding surface reduces.The landslide thrust,soil resistance and pile displacement increase;and the increment rates become larger.In addition,based on the test results,reasonable values of seismic coefficient Czare proposed for the structure;and the values of Cz are 0.2,0.35 and 0.4 in the seismic zones of basic intensity Ⅶ,Ⅷ and Ⅸ respectively.The test results are helpful to reveal the seismic mechanism and can provide reliable basis for seismic design of anti-sliding sheet pile wall.
From the investigation of seismic hazards of subgrade in Wenchuan earthquake,the anti-sliding sheet pile wall has been proven to be an excellent seismic structure in bedding or accumulation slopes.In order to understand the seismic performance better and optimize the seismic design,large shaking table test is performed.In order to ascertain the seismic response characteristics of anti-sliding sheet pile wall,acceleration histories recorded at Wolong station in Wenchuan earthquake are scaled and used to excite the model.The test results reveal the distribution pattern of earth pressure along the pile,seismic response of displacement and accelerations in slopes under ground shaking.The research demonstrates that the distribution of seismic earth pressure is nonlinear along the pile;and vertical seismic load has amplification effect on horizontal acceleration.Therefore,the seismic earth pressure under bidirectional loads is larger than that under unidirectional horizontal load.However,the difference between them is not obvious in seismic zones of basic intensity Ⅶ and Ⅷ.Furthermore,landslide thrust,soil resistance of sliding bed,and displacement of pile are proportional to the input seismic peak acceleration.It means that,with the increase of input peak seismic acceleration,the amplification ratio of acceleration increases and the material shear strength of sliding surface reduces.The landslide thrust,soil resistance and pile displacement increase;and the increment rates become larger.In addition,based on the test results,reasonable values of seismic coefficient Czare proposed for the structure;and the values of Cz are 0.2,0.35 and 0.4 in the seismic zones of basic intensity Ⅶ,Ⅷ and Ⅸ respectively.The test results are helpful to reveal the seismic mechanism and can provide reliable basis for seismic design of anti-sliding sheet pile wall.
引文
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[12]蒋良潍,姚令侃,王建.基于振动性态和破坏相似的边坡振动台模型实验相似律[J].交通科学与工程,2009,25(2):1-7.JIANG Liang-wei,YAO Ling-kan,WANG Jian.Similitude for shaking table model test on side sloperelating to dynamic characteristics and strength[J].Journal of Transport Science and Engineering,2009,25(2):1-7.
[13]楼梦麟,王文剑,马恒春,等.土-桩-结构相互作用体系的振动台模型试验[J].同济大学学报,2001,29(7):763-768.LOU Meng-lin,WANG Wen-jian,MA Heng-chun,et al.Study of soil-pile-structure interaction system by shakingtable model test[J].Journal of Tongji University,2001,29(7):763-768.
[2]铁道部第二勘测设计院.抗滑桩设计与计算[M].北京:中国铁道出版,1983.
[3]张建经,冯君,肖世国,等.支挡结构抗震设计的两个关键技术问题[J].西南交通大学学报,2009,44(3):321-326.ZHANG Jian-jing,FENG Jun,XIAO Shi-guo,et al.Discussions on two key technical problems for seismicdesign of retaining structures[J].Journal of SouthwestJiaotong University,2009,44(3):321-326.
[4]姚令侃,冯俊德,杨明.汶川地震路基震害分析及对抗震规范改进的启示[J].西南交通大学学报,2009,44(3):301-311.YAO Ling-kan,FENG Jun-de,YANG Ming.Damageanalysis of subgrade engineering in Wenchuan earthquakeand recommendations for improving seismic designcode[J].Journal of Southwest Jiaotong University,2009,44(3):301-311.
[5]周德培,张建经,汤涌.汶川地震中道路边坡工程震害分析[J].岩石力学与工程学报,2010,29(3):565-576.ZHOU De-pei,ZHANG Jian-jing,TANG Yong.Seismicdamage analysis of road slopes in Wenchuanearthquake[J].Chinese Journal of Rock Mechanics andEngineering,2010,29(3):565-576.
[6]The Bromeliad Society International.Eurocode 8:Designof structures for earthquake resistance Part 5:Foundations,retaining structures and geotechnical aspects[S].Brussel:European Committee for Standardization,1998.
[7]SATOH H,OHBO N,YOSHIZAKO K.Dynamic test onbehavior of pile during lateral ground flow[C]//Centrifuge98.Rotterdam:A.A.Balkema,1998:327-332.
[8]ABDOUN T,DOBRY R.Pile response to lateral spreads:Centrifuge modeling[J].Journal of Geotechnical andGeoenvironmental Engineering,2003,129(10):869-878.
[9]TAKAHASHI A,TAKEMURA J,KAWAGUCHIY,et al.Stability of piled pier subjected to lateral flow of soilsduring earthquake[C]//Centrifuge 98.Rotterdam:A.A.Balkema,1998:365-370.
[10]陶云辉.地震条件下桩板结构受力分析[D].成都:西南交通大学,2008.
[11]魏宏.玉蒙铁路路堤桩板墙振动台模型试验研究[D].成都:西南交通大学,2010.
[12]蒋良潍,姚令侃,王建.基于振动性态和破坏相似的边坡振动台模型实验相似律[J].交通科学与工程,2009,25(2):1-7.JIANG Liang-wei,YAO Ling-kan,WANG Jian.Similitude for shaking table model test on side sloperelating to dynamic characteristics and strength[J].Journal of Transport Science and Engineering,2009,25(2):1-7.
[13]楼梦麟,王文剑,马恒春,等.土-桩-结构相互作用体系的振动台模型试验[J].同济大学学报,2001,29(7):763-768.LOU Meng-lin,WANG Wen-jian,MA Heng-chun,et al.Study of soil-pile-structure interaction system by shakingtable model test[J].Journal of Tongji University,2001,29(7):763-768.
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