基于耦合方法的挡土墙地震响应的数值模拟
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摘要
为有效描述动力灾变过程中挡土墙附近土体的细观特性,并大量减小离散元模拟的颗粒数目,节省计算时间,利用离散-连续耦合动力数值模型,模拟了已有离心机试验中重力式挡土墙的地震响应。靠近挡土墙的土体区域用相互作用的离散颗粒模拟,远离挡土墙的土体采用连续模型模拟,编写结构的动力有限元程序并嵌入离散元软件中来模拟挡土墙。通过离散元软件PFC2D和有限差分软件FLAC2D的交互运算实现耦合过程。耦合方法的核心在于:①在离散-连续土体的交界面保证连续性;②模拟中离散区域土体的宏观性质与连续土体模型一致。为进一步满足以上两点,分别提出了新的边界耦合力提取方法和自振柱模拟方法。研究表明耦合方法可以从细观尺度上有效描述土体与结构的相互作用和关心区域的土体特性。
In order to depict the discrete properties near the retaining wall on the meso-scale,while efficiently reduce particle numbers and save computation time,based on coupled discrete-continuous approach,a retaining wall under seismic excitation in centrifuge model test is simulated. Particle flow code(PFC),which is based on discrete element method,is used to simulate sands near the retaining wall,while the domain containing particles away from the retaining wall is simulated as continuous media by the fast Lagrange analysis of continua (FLAC). The motion of the retaining wall is governed by a self-edited dynamic finite element program which is added to PFC. Coupling is achieved by interchanging data between the two software during each time step. The essence of the coupled approach includes two parts:(1) fulfilling the continuity between the discrete and continuous domains; (2) the macro parameters of the granular material should be in accordance with those used in continuous model. A new approach for picking up coupled forces and a free-vibration column simulation method are presented as supplements to satisfy the two above mentioned requirements respectively. It is shown that,on the meso-scale,the coupled method can well describe the concerned zone and the interaction between the retaining wall and the particles.
In order to depict the discrete properties near the retaining wall on the meso-scale,while efficiently reduce particle numbers and save computation time,based on coupled discrete-continuous approach,a retaining wall under seismic excitation in centrifuge model test is simulated. Particle flow code(PFC),which is based on discrete element method,is used to simulate sands near the retaining wall,while the domain containing particles away from the retaining wall is simulated as continuous media by the fast Lagrange analysis of continua (FLAC). The motion of the retaining wall is governed by a self-edited dynamic finite element program which is added to PFC. Coupling is achieved by interchanging data between the two software during each time step. The essence of the coupled approach includes two parts:(1) fulfilling the continuity between the discrete and continuous domains; (2) the macro parameters of the granular material should be in accordance with those used in continuous model. A new approach for picking up coupled forces and a free-vibration column simulation method are presented as supplements to satisfy the two above mentioned requirements respectively. It is shown that,on the meso-scale,the coupled method can well describe the concerned zone and the interaction between the retaining wall and the particles.
引文
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[2]周健,彭述权,樊玲.刚性挡土墙主动土压力颗粒流模拟[J].岩土力学,2008,29(3):629-638.ZHOU Jian,PENG Shu-quan,FAN Ling.Particle flow simulation of active earth pressure distribution on rigid retaining wall[J].Rock and Soil Mechanics,2008,29(3):629-638.
[3]曾庆有,周健.不同墙体位移方式下被动土压力的颗粒流模拟[J].岩土力学,2005,26(增刊):43-47.ZENG Qing-you,ZHOU Jian.Analysis of passive earth pressure due to various wall movement by particle flow code(2D)[J].Rock and Soil Mechanics,2005,26(Supp.):43-47.
[4]CUNDALL P A.PFC user manual[M].Minneapolis:Itasca Consulting Group Inc.,2004.
[5]周健,史旦达,贾敏才,等.循环加荷条件下饱和砂土液化细观数值模拟[J].水利学报,2007,38(6):697-703.ZHOU Jian,SHI Dan-da,JIA Min-cai,et al.Micro-mechanical simulation of liquefaction behavior of saturated sand under cyclic loading[J].Journal of Hydraulic Engineering,2007,38(6):697-703.
[6]LUBEN I.TODOROVSKI.An experimental study on the kinetics of a free-standing retaining wall under seismic excitation[D].[S.l].:College Station,Texas A&M University,1998.
[7]姜朴.现代土工测量技术[M].北京:中国水利水电出版社,1996.
[8]BRAJA M DAS.土动力学原理[M].吴世明,顾尧章译.杭州:浙江大学出版社,1984.
[9]LI Xiang-song.Laboratory determination of shearmodulus and damping of soils using a microcomputer based instrumentation system[D].Davis:University of California at Davis,1982.
[10]顾尧章,李相崧,沈智刚.土动力学中的自振柱试验[J].土木工程学报,1984,17(2):39-47.GU Yao-zhang,LI Xiang-son,SHEN C K.A free-vibrating column test in soil dynamics[J].China Civil Engineering Journal,1984,17(2):39-47.
[11]皱泾湘.结构动力学[M].哈尔滨:哈尔滨工业大学出版社,1996.
[12]徐稼轩,郑铁生.结构动力分析的数值方法[M].西安:西安交通大学出版社,1993.
[13]CUNDALL P A.FLAC user manual[M].Minneapolis:Itasca Consulting Group Inc.,1998.
[14]YOKOYAMA T.Vibration of a hanging Timoshenko beam under gravity[J].Journal of Sound and Vibration,1990,151(2):245-258.
[15]ZIENKIEWICZ O C,TAYOR R L.Finite element method volume1-the basis[M].Butterworth:Heinemann,2000.
[16]LECHOSLAW G BIERAWSKI,SHIRO MAENO.DEM-FEM model of hightly saturated soil motion due to seepage force[J].Journal of Waterway,Port,Coastal and Ocean Engineering,2006,132(5):401-409.
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