土石坝拟静力抗震稳定性分析与坝坡地震滑移量估算
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摘要
单独采用拟静力抗震稳定性安全系数,并不能准确地评价土石坝的动力稳定性,Newmark等采用刚塑体滑移量或永久变形评价土石坝地震稳定性的建议得到了逐步认同,但土石坝地震永久变形或滑移量的估算尚缺乏合理方法。为此,将土石坝地震动力响应分析和拟静力极限平衡分析相结合,提出了合理地估算坝坡上潜在滑坡体地震滑移量的数值计算方法。首先,根据土石坝地震动力响应分析,针对圆弧滑动面和非圆弧光滑渐变曲面形式滑动面,分别采用简化Bishop法及改进的简化Bishop法计算坝坡上潜在滑动体的各个时刻拟静力安全系数。随后,对其中安全系数小于1的瞬时超载阶段,通过时间积分确定潜在滑动体的滑移量。最后,结合算例并通过具体数值计算与分析探讨了竖向地震动分量、滑坡体竖向地震响应、振动孔隙水压力等各种因素对土石坝地震位移及抗震性能的影响。
It has been well recognized that the safety of embankments during earthquake cannot be evaluated solely by the safety factor of the pseudo-static stability.It is suggested by Newmark that the seismic stability of embankment should be assessed by using the seism-induced sliding movements or permanent deformations instead of the overall safety factor.However,the rational evaluation of sliding movements or residual deformations induced during earthquake cannot be made in a perfect manner.In this paper,a numerical procedure is proposed for evaluating the sliding movements of embankments based on the step-by-step dynamic response analysis and the pseudo-static limit-equilibrium analysis.In the proposed method,the dynamic responses of embankments to earthquake shaking are first predicted by FEM-based numerical analysis.The simplified Bishop’s procedure and modified simplified Bishop’s procedure of limit equilibrium are employed to evaluate the transient safety factors of potential sliding mass of embankment slopes respectively for circle slip surface and for smoothed non-circle slip surface.For the overloading in which the transient safety factor is lower than unity;the transient sliding movement can be assessed by double integration with respect to time.For the example case,the parametric computations and comparative studies are made to examine the effect of vertical component of ground motions,vertical seismic response of potential sliding mass,shaking-induced pore water pressure and other related factors on the sliding movement and earthquake-resistant behavior of embankments.
It has been well recognized that the safety of embankments during earthquake cannot be evaluated solely by the safety factor of the pseudo-static stability.It is suggested by Newmark that the seismic stability of embankment should be assessed by using the seism-induced sliding movements or permanent deformations instead of the overall safety factor.However,the rational evaluation of sliding movements or residual deformations induced during earthquake cannot be made in a perfect manner.In this paper,a numerical procedure is proposed for evaluating the sliding movements of embankments based on the step-by-step dynamic response analysis and the pseudo-static limit-equilibrium analysis.In the proposed method,the dynamic responses of embankments to earthquake shaking are first predicted by FEM-based numerical analysis.The simplified Bishop’s procedure and modified simplified Bishop’s procedure of limit equilibrium are employed to evaluate the transient safety factors of potential sliding mass of embankment slopes respectively for circle slip surface and for smoothed non-circle slip surface.For the overloading in which the transient safety factor is lower than unity;the transient sliding movement can be assessed by double integration with respect to time.For the example case,the parametric computations and comparative studies are made to examine the effect of vertical component of ground motions,vertical seismic response of potential sliding mass,shaking-induced pore water pressure and other related factors on the sliding movement and earthquake-resistant behavior of embankments.
引文
[1]李湛,栾茂田.土工建筑物地震永久滑移简化计算方法研究进展评述[J].防灾减灾工程学报,2005,25(2):227-234.LI Zhan,LUAN Mao-tian.State-of-the-art review on simplified procedures for evaluation of seismically-induced sliding deformation of earth structures[J].Journal of Disaster Prevention and Mitigation Engineering,2005,25(2):227-234.
[2]Newmark N M.Effects of earthquakes on dams and embankments[J].Geotechnique,1965,15(2):139-160.
[3]Makdisi F I,Seed H B.Simplified procedure for estimation dam and embankment earthquake induced deformations[J].Journal of the Geotechnical Eng-ineering,Division,ASCE,1978,104(7):849-868.
[4]Chang C J,Chen W F,Yao James T P.Seismic displacement in slopes by limit analysis[J].Journal of the Geotechnical Engineering Division,ASCE,1984,110(7):860-874.
[5]Luan Maotian,Jin Chongpan,Lin Gao.Evaluation technique for earthquake-induced movements and dynamic stability of embankments[A].In:Luan Maotian,Keizo Ugai ed.Proceeding of the Special Sino-Japanese Forum on Performance and Evaluation of Soil Slopes under Earthquakes and Rainstorms[C].Dalian:Dalian University of Technology Press,1998.116-131.
[6]Sarma S K.Seismic stability of earth dams and embankments[J].Geotechnique,1975,25(4):74-761.
[7]Biondi G,Cascone G,Maugeri M.Flow and deformation failure of sandy slopes[J].Soil Dynamics and Ear-thquake Engineering,2002,22(9-12):1 103-1 114.
[8]Lin J S,Whiteman R V.Decoupling approximation to the evaluation of earthquake-induced plastic slip in earth dams[J].Earthquake Engineering and Structural Dynamics,1983,11(5):667-678.
[9]Gazetas G,Uddin N.Permanent deformation on preexisting sliding surfaces in dams[J].Journal of Geotechnical Engineering,ASCE,1994,120(11):2 041-2 061.
[10]Wartman J,Bray J D,Seed R B.Shaking table experimental of a model slope subjected to a pair of repeated ground motions[A].Proceedings of Fourth International Conference on Recent Advance in Geotechnical Earthquake Engineering and Soil Dynamics[C].California:San Diego,2001.5-14.
[11]Kramer S L,Smith M W.Modified Newmark model for seismic displacements of compliant slopes[J].Journal of Geotechnical and Geoenvironmental Engineering,ASCE,1997,123(7):635-644.
[12]Rathje E M,Bray J D.Nonlinear coupled seismic analysis of earth structures[J].Journal of Geotechnical and Geoenvironmental Engineering,ASCE,2000,126(11):1 002-1 015.
[13]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.2-D dynamic analysis of effective stresses of seismic liquefaction[J].Journal of East China College of Hydraulic Engineering,1981,9(3):1-14.
[14]张天宝.土坡稳定分析和土工建筑物的边坡设计[M].成都:成都科技大学出版社,1987.
[15]张鲁渝,郑颖人.简化Bishop法的扩展及其在非圆弧滑面中的应用[J].岩土力学,2004,25(6):927-934.ZHANG Lu-yu,ZHENG Ying-ren.An extension of simplified Bishop method and its application to non-circular slip surface for slope stability analysis[J].Rock and Soil Mechanics,2004,25(6):927-934.
[16]李湛,栾茂田.考虑强度退化效应的堤坝抗震稳定性评价方法[J].岩土力学,2004,25(增刊2):409-413.LI Zhan,LUAN Mao-tian.Evaluation of aseismic stability of soil embankments considering cyclic degradation of soil strength[J].Rock and Soil Mechanics,2004,25(Supp2.):409-413.
[17]Stamatopoulos C A.Sliding system predicting large permanent co-seismic movements of slopes[J].Earthquake Engineering and structural Dynamics,1996,25(10):1 075-1 093.
[18]Ambraseys N,Srbulov M.Earthquake induced displacements of slopes[J].Soil Dynamics and Earthquake Engineering,1995,14(1):59-71.
[19]汪闻韶,金崇磐,王克成.土石坝的抗震计算和模型实验及原型观测[J].水利学报,1987,(12):1-15.WANG Wen-shao,JIN Chong-pan,WANG Ke-cheng.Aseismatic calculation,model and prototype experiments and field monitoring of earth-rock dams[J].Journal of Hydraulic Engineering,1987,(12):1-15.
[2]Newmark N M.Effects of earthquakes on dams and embankments[J].Geotechnique,1965,15(2):139-160.
[3]Makdisi F I,Seed H B.Simplified procedure for estimation dam and embankment earthquake induced deformations[J].Journal of the Geotechnical Eng-ineering,Division,ASCE,1978,104(7):849-868.
[4]Chang C J,Chen W F,Yao James T P.Seismic displacement in slopes by limit analysis[J].Journal of the Geotechnical Engineering Division,ASCE,1984,110(7):860-874.
[5]Luan Maotian,Jin Chongpan,Lin Gao.Evaluation technique for earthquake-induced movements and dynamic stability of embankments[A].In:Luan Maotian,Keizo Ugai ed.Proceeding of the Special Sino-Japanese Forum on Performance and Evaluation of Soil Slopes under Earthquakes and Rainstorms[C].Dalian:Dalian University of Technology Press,1998.116-131.
[6]Sarma S K.Seismic stability of earth dams and embankments[J].Geotechnique,1975,25(4):74-761.
[7]Biondi G,Cascone G,Maugeri M.Flow and deformation failure of sandy slopes[J].Soil Dynamics and Ear-thquake Engineering,2002,22(9-12):1 103-1 114.
[8]Lin J S,Whiteman R V.Decoupling approximation to the evaluation of earthquake-induced plastic slip in earth dams[J].Earthquake Engineering and Structural Dynamics,1983,11(5):667-678.
[9]Gazetas G,Uddin N.Permanent deformation on preexisting sliding surfaces in dams[J].Journal of Geotechnical Engineering,ASCE,1994,120(11):2 041-2 061.
[10]Wartman J,Bray J D,Seed R B.Shaking table experimental of a model slope subjected to a pair of repeated ground motions[A].Proceedings of Fourth International Conference on Recent Advance in Geotechnical Earthquake Engineering and Soil Dynamics[C].California:San Diego,2001.5-14.
[11]Kramer S L,Smith M W.Modified Newmark model for seismic displacements of compliant slopes[J].Journal of Geotechnical and Geoenvironmental Engineering,ASCE,1997,123(7):635-644.
[12]Rathje E M,Bray J D.Nonlinear coupled seismic analysis of earth structures[J].Journal of Geotechnical and Geoenvironmental Engineering,ASCE,2000,126(11):1 002-1 015.
[13]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.2-D dynamic analysis of effective stresses of seismic liquefaction[J].Journal of East China College of Hydraulic Engineering,1981,9(3):1-14.
[14]张天宝.土坡稳定分析和土工建筑物的边坡设计[M].成都:成都科技大学出版社,1987.
[15]张鲁渝,郑颖人.简化Bishop法的扩展及其在非圆弧滑面中的应用[J].岩土力学,2004,25(6):927-934.ZHANG Lu-yu,ZHENG Ying-ren.An extension of simplified Bishop method and its application to non-circular slip surface for slope stability analysis[J].Rock and Soil Mechanics,2004,25(6):927-934.
[16]李湛,栾茂田.考虑强度退化效应的堤坝抗震稳定性评价方法[J].岩土力学,2004,25(增刊2):409-413.LI Zhan,LUAN Mao-tian.Evaluation of aseismic stability of soil embankments considering cyclic degradation of soil strength[J].Rock and Soil Mechanics,2004,25(Supp2.):409-413.
[17]Stamatopoulos C A.Sliding system predicting large permanent co-seismic movements of slopes[J].Earthquake Engineering and structural Dynamics,1996,25(10):1 075-1 093.
[18]Ambraseys N,Srbulov M.Earthquake induced displacements of slopes[J].Soil Dynamics and Earthquake Engineering,1995,14(1):59-71.
[19]汪闻韶,金崇磐,王克成.土石坝的抗震计算和模型实验及原型观测[J].水利学报,1987,(12):1-15.WANG Wen-shao,JIN Chong-pan,WANG Ke-cheng.Aseismatic calculation,model and prototype experiments and field monitoring of earth-rock dams[J].Journal of Hydraulic Engineering,1987,(12):1-15.
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