土石坝拟静力抗震稳定分析的强度折减有限元法
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摘要
基于拟静力抗震设计概念,提出利用强度折减有限单元法分析土石坝的抗震稳定性,给出了两种确定地震惯性力的方法:(1)依据《水工建筑物抗震设计规范》[1],并结合有关土石坝动态分布系数计算了沿坝高分布的地震惯性力;(2)直接利用土石坝有限元地震动力反应分析得到的单元节点加速度反应,依据建议的方法确定坝体各单元节点的地震惯性力。将上述计算确定的地震惯性力与其他形式的外荷载共同作用到土石坝上,采用强度折减有限元法确定土石坝坝体的拟静力抗震安全系数。对于稳定渗流期,水位降落期等不同工况,或需要考虑振动孔隙水压力作用的饱和无黏性土填筑坝等不同计算条件,给出了使用折减强度有限元法分析坝体抗震稳定性的实现途径和方法。研究表明,有限元法对边界条件、复杂断面条件和材料分区及荷载组合均具有较强的适应能力,因此,使用有限元法分析土石坝抗震稳定性具有显著的优越性。
An analysis procedure based on shear strength reduction finite element method for pseudo-static seismic stability calculation of earth and rockfill dam(ERFD) is presented.In the proposed procedure,two methods are proposed to determine the seism-induced inertia force:(1) the inertia forces are computed with the same method adopted in the pseudo-static limit equilibrium slices method;(2) with the absolute acceleration response of element nodes obtained from the finite element dynamic response analysis of the dam,the inertia forces corresponding to the node acceleration are computed with the proposed empirical method.With the inertia forces achieved above,the self-gravity,and/or the forces corresponding to the seepage force or dynamic pore water pressure,the elastoplastic finite element analysis is conducted to achieve the pseudo-static factor of safety of the dam by reducing the effective shear strength parameters of soil until the limit equilibrium is reached.Finally,numerical computations are conducted to illustrate the proposed analysis method;and the results are compared with those obtained from the pseudo-static limit equilibrium method.It is concluded that the utilization of the finite element method for aseismic stability analysis of ERFD is feasible.
An analysis procedure based on shear strength reduction finite element method for pseudo-static seismic stability calculation of earth and rockfill dam(ERFD) is presented.In the proposed procedure,two methods are proposed to determine the seism-induced inertia force:(1) the inertia forces are computed with the same method adopted in the pseudo-static limit equilibrium slices method;(2) with the absolute acceleration response of element nodes obtained from the finite element dynamic response analysis of the dam,the inertia forces corresponding to the node acceleration are computed with the proposed empirical method.With the inertia forces achieved above,the self-gravity,and/or the forces corresponding to the seepage force or dynamic pore water pressure,the elastoplastic finite element analysis is conducted to achieve the pseudo-static factor of safety of the dam by reducing the effective shear strength parameters of soil until the limit equilibrium is reached.Finally,numerical computations are conducted to illustrate the proposed analysis method;and the results are compared with those obtained from the pseudo-static limit equilibrium method.It is concluded that the utilization of the finite element method for aseismic stability analysis of ERFD is feasible.
引文
[1]中国水电水利科学研究院.SL203-97水工建筑物抗震设计规范[S].北京:中国水利水电出版社,1997.
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[8]刘金龙,栾茂田,赵少飞,等.关于强度折减有限元方法中边坡失稳判据的讨论[J].岩土力学,2005,26(8):1345-1348.LIU Jin-long,LUAN Mao-tian,ZHAO Shao-fei,et al.Discussion on criteria for evaluating stability of slope inelastoplastic FEM based on shear strength reductiontechnique[J].Rock and Soil Mechanics,2005,26(8):1345-1348.
[9]李湛,栾茂田,刘占阁,等.渗流作用下边坡稳定性分析的强度折减弹塑性有限元法[J].水利学报,2006,(5):554-559.LI Zhan,LUAN Mao-tian,LIU Zhan-ge,et al.Elasto-plastic finite element method based on the technique ofshear strength reduction for stability analysis of dams andembankments under seepage[J].Journal of HydraulicEngineering,2006,(5):554-559.
[10]顾淦臣.土石坝地震工程[M].南京:河海大学出版社,1990.
[11]徐志英,沈珠江.地震液化的有效应力二维动力分析方法[J].华东水利学院学报,1981,9(3):1-14.XU Zhi-ying,SHEN Zhu-jiang.Two-dimensionaleffective-stress dynamic analysis method of earthquakeinduced liquefaction[J].Journal of Eastern ChinaHydraulic Engineering College,1981,9(3):1-14.
[12]TANIGUCHI E,WHITMAN R V,MARR W A.Predic-tion of earthquake induced deformation of earth dams[J].Soils and Foundations,1983,23(4):126-132.
[2]DONALD I B.Finite element assessment of slopestability[R].Melbourne,Australia:Dept.of CivilEngineering,Monash University,1993:1-18.
[3]BISHOP A W.The use of the slip circle in stabilityanalysis of slope[J].Geotechnique,1955,5(1):7-17.
[4]ZIENKIEWICZ O C,HUMPHESON C,LEWIS R W.Associated and non-associated visco-plasticity andplasticity in soil mechanics[J].Geotechnique,1975,25(4):671-689.
[5]GRIFFITHS D V,LANE P A.Slope stability analysis byfinite elements[J].Geotechnique,1999,49(3):387-403.
[6]郑颖人,赵尚毅,孔位学,等.极限分析有限元法讲座——Ⅰ岩土工程极限分析有限元法[J].岩土力学,2005,26(1):163-168.ZHENG Ying-ren,ZHAO Shang-yi,KONG Wei-xue,et al.Geotechnical engineering limit analysis using finiteelement method[J].Rock and Soil Mechanics,2005,26(1):163-168.
[7]赵尚毅,郑颖人,张玉芳.极限分析有限元法讲座——Ⅱ有限元强度折减法中边坡失稳的判据探讨[J].岩石力学与工程学报,2005,26(2):332-336.ZHAO Shang-yi,ZHENG Ying-ren,ZHANG Yu-fang.Study on slope failure criterion in strength reduction finiteelement method[J].Chinese Journal of Rock Mechanicsand Engineering,2005,26(2):332-336.
[8]刘金龙,栾茂田,赵少飞,等.关于强度折减有限元方法中边坡失稳判据的讨论[J].岩土力学,2005,26(8):1345-1348.LIU Jin-long,LUAN Mao-tian,ZHAO Shao-fei,et al.Discussion on criteria for evaluating stability of slope inelastoplastic FEM based on shear strength reductiontechnique[J].Rock and Soil Mechanics,2005,26(8):1345-1348.
[9]李湛,栾茂田,刘占阁,等.渗流作用下边坡稳定性分析的强度折减弹塑性有限元法[J].水利学报,2006,(5):554-559.LI Zhan,LUAN Mao-tian,LIU Zhan-ge,et al.Elasto-plastic finite element method based on the technique ofshear strength reduction for stability analysis of dams andembankments under seepage[J].Journal of HydraulicEngineering,2006,(5):554-559.
[10]顾淦臣.土石坝地震工程[M].南京:河海大学出版社,1990.
[11]徐志英,沈珠江.地震液化的有效应力二维动力分析方法[J].华东水利学院学报,1981,9(3):1-14.XU Zhi-ying,SHEN Zhu-jiang.Two-dimensionaleffective-stress dynamic analysis method of earthquakeinduced liquefaction[J].Journal of Eastern ChinaHydraulic Engineering College,1981,9(3):1-14.
[12]TANIGUCHI E,WHITMAN R V,MARR W A.Predic-tion of earthquake induced deformation of earth dams[J].Soils and Foundations,1983,23(4):126-132.
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