软弱地基浅埋地铁区间隧洞的地震反应分析
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摘要
针对南京地铁建设的实际背景和南京软弱地基的特点,以某典型软弱地基浅埋地铁区间隧洞为研究对象,对该软弱场地土的动参数进行了室内外试验研究,给出了各类土的剪切模量比G/Gmax和阻尼比λ与剪应变幅值γ之间的关系曲线,以及各土层的剪切波速;同时,采用等效线性化模型描述土的非线性性能,考虑地基土与地下浅埋隧洞动力相互作用的影响,采用二维有限元整体分析法对软弱地基浅埋隧洞的地震反应进行了数值模拟。计算结果表明:软土地基上的浅埋隧洞在中强地震发生时,在衬砌内引起很大的轴向力、剪力和弯矩,使得软土地基上浅埋隧洞在地震荷载作用下距离洞顶和洞底±35°左右的地方很容易发生剪切和弯剪破坏,这与已有地下隧道的震害是非常吻合的,因此该计算结果对地下区间隧道的抗震设计具有重要的参考价值。
By considering the characteristics of soft soils in Nanjing city,a representative soft foundation is selected to be investigated.Firstly,the curves of dynamic shear modulus ratio G/Gmax and damping ratio versus dynamic strain γ of the soils in this site are obtained by GZZ-1 free vibration column test system improved by Nanjing University of Technology.Secondly,as far as the Nanjing Subways are concerned,the earthquake response of shallow subway tunnels in soft foundation is analyzed by 2D finite element method.In the calculation model,the effect of soil-tunnel dynamic interaction and the nonlinear behavior of soil are considered by the equivalent linear method.It is shown that the force induced by middle and strong ground motions are very large.The damages are very likely to occur at places with central angles of ±35° or so to the top and bottom of the tunnels.These conclusions are in good agreement with records of seismic damage of subway.
By considering the characteristics of soft soils in Nanjing city,a representative soft foundation is selected to be investigated.Firstly,the curves of dynamic shear modulus ratio G/Gmax and damping ratio versus dynamic strain γ of the soils in this site are obtained by GZZ-1 free vibration column test system improved by Nanjing University of Technology.Secondly,as far as the Nanjing Subways are concerned,the earthquake response of shallow subway tunnels in soft foundation is analyzed by 2D finite element method.In the calculation model,the effect of soil-tunnel dynamic interaction and the nonlinear behavior of soil are considered by the equivalent linear method.It is shown that the force induced by middle and strong ground motions are very large.The damages are very likely to occur at places with central angles of ±35° or so to the top and bottom of the tunnels.These conclusions are in good agreement with records of seismic damage of subway.
引文
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[2]刘钊,佘才高,周振强.地铁工程设计与施工[M].北京:人民交通出版社,2004.(Liu Zhao,She Caigao,Zhou Zhenqiang.Design and Construction of Metro Engineering[M].Beijing:China Communications Press,2004.(in Chinese))
[3]Hong S H,Lee F H,Yong K Y.Three-dimensional pile-soil interaction in soldier-piled excavations[J].Computers and Geotechnics,2003,30(1):81-107.
[4]Spyrakos C,Loannidis G.Seismic behavior of a post-tensioned integral bridge including soil-structure interaction(SSI)[J].Soil Dynamics and Earthquake Engineering,2003,23(1):53-63.
[5]Ostadan F,Penzien J.Seismic design of cut-and-cover section of the bay area rapid transit extension to San Francisco Airport[A].In:Proceedings of2nd US-Japan SSI Workshop[C].Japan,Tsukuba:[s.n.],2001.1-16.
[6]Huo H B,Bobet A.Seismic design of cut and cover rectangular tunnels-evaluation of observed behavior of Dakai station during Kobe earthquake,1995[A].In:Proceedings of1st World Forum of Chinese Scholars in Geotechnical Engineering[C].Shanghai:[s.n.],2003.456-466.
[7]Nishioka T,Unjoh S.A simplified seismic design method for underground structure based on the shear strain transmitting characteristics[R].Minamihara,Tsukuba:Public Works Research Institute,2000.
[8]刘雪珠.南京及其邻近地区新近沉积土的动力特性和砂土震动液化研究[博士学位论文][D].南京:南京工业大学,2003.(Liu Xuezhu.The study and test on dynamic properties of recently deposited soils and vibratory liquidation of sands in Nanjing area and its neighbor[Ph.D.Thesis][D].Nanjing:Nanjing University of Technology,2003.(in Chinese))
[9]陈国兴,杨伟林,严新育.南京河西地区软土场地地震动参数研究[J].南京工业大学学报(自然科学版),2002,24(1):35-40.(Chen Guoxing,Yang Weiling,Yan Xinyu.A study of design ground motion parameters in Hexi area of Nanjing city[J].Journal of Nanjing University of Technology(Natural Science Edition),2002,24(1):35-40.(in Chinese))
[10]陈国兴.土体-结构体系抗震性能整体分析方法与程序开发研究[J].南京建筑工程学院学报,1997,(2):1-7.(Chen Guoxing.An integrated system analysis procedure and development of software package for analyzing the seismic behavior of the soil-structure system[J].Journal of Nanjing Architectural and Civil Engineering Institute,1997,(2):1-7.(in Chinese))
[11]季倩倩,杨林德.地下铁道震害与震后修复措施[J].灾害学,2001,16(2):31-36.(Ji Qianqian,Yang Linde.Seismic damage and restoration measures of subway[J].Journal of Catastrophology,2001,16(2):31-36.(in Chinese))
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