水平向与竖向地震动的时间遇合模式对边坡动力安全系数的影响
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摘要
通过沿滑面的应力积分法和动力时程分析法,研究了水平向、竖向地震动单独作用对边坡动安全系数的影响,发现竖向地震动与水平向地震动一样也对边坡抗震稳定性有显著的影响。在此基础之上,重点探讨了实际地震的双向地震动同时作用时,其时间遇合模式对动力安全系数的影响,结果表明,常用的加速度峰值遇合模式和随机遇合模式都不能充分体现出竖向地震动与水平向地震动的叠加效应,进而造成对安全系数的高估;文中提出的最大地震作用效应遇合模式才是最危险的遇合模式,其所得稳定性安全系数时程的极值更小。在考虑多向地震的边坡抗震分析中,由于多维地震动的强烈随机性,应考虑出现这种最大地震作用效应遇合的可能性,以得到工程设计中偏于安全的动力稳定性安全系数值。
Firstly,influence of only horizontal or vertical earthquake loading on slope seismic safety factor is examined using stress integration along sliding surface and the dynamic FEM time-history analysis method.It is shown that under most conditions the vertical ground motion has the same significant effect on slope stability as the horizontal earthquake motion.Then,the effects of the time combination pattern of horizontal and vertical accelerograms on the dynamic safety factor are considered.It is concluded from the analysis results that the pattern with peak acceleration values meeting in time domain and the random time combination pattern may lead to over estimation of safety factors because of not giving the most significant superimposing effect for the vertical earthquake loading and the pattern with maximum action effects meeting in time domain is the severest pattern which allows for the minimum value of safety factor to be obtained.Due to the largely unknown behavior and random nature of earthquakes,the possibility for the pattern with maximum action effects meeting in time domain should be considered for slope under multiple-dimensional earthquake action to get the more conservative safety factor for the engineering design.
Firstly,influence of only horizontal or vertical earthquake loading on slope seismic safety factor is examined using stress integration along sliding surface and the dynamic FEM time-history analysis method.It is shown that under most conditions the vertical ground motion has the same significant effect on slope stability as the horizontal earthquake motion.Then,the effects of the time combination pattern of horizontal and vertical accelerograms on the dynamic safety factor are considered.It is concluded from the analysis results that the pattern with peak acceleration values meeting in time domain and the random time combination pattern may lead to over estimation of safety factors because of not giving the most significant superimposing effect for the vertical earthquake loading and the pattern with maximum action effects meeting in time domain is the severest pattern which allows for the minimum value of safety factor to be obtained.Due to the largely unknown behavior and random nature of earthquakes,the possibility for the pattern with maximum action effects meeting in time domain should be considered for slope under multiple-dimensional earthquake action to get the more conservative safety factor for the engineering design.
引文
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[11]刘汉龙,费康,高玉峰.边坡地震稳定性时程分析方法[J].岩土力学,2003,24(4):553-556.LIU Han-long,FEI Kang,GAO Yu-feng.Time history analysis method of slope seismic stability[J].Rock and Soil Mechanics,2003,24(4):553-556.
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[13]中国水利水电科学研究院.DL5073-2000水工建筑物抗震设计规范[S].北京:中国电力出版社,2003.
[14]JOSEPH PENZIEN,MAKOTOWATABE.Characteristics of 3-dimensional earthquake ground motions[J].Earthquake Engineering and Structural Dynamics,1975,3:365-373.
[2]黄润秋.汶川8.0级地震触发崩滑灾害机制及其地质力学模式[J].岩石力学与工程学报,2009,28(6):1239-1249.HUANG Run-qiu.Mechanism and geomechanical modes of landslide hazards triggered by wenchuan8.0earthquake[J].Chinese Journal of Rock Mechanics and Engineering,2009,28(6):1239-1249.
[3]刘红帅,薄景山,刘德东.岩土边坡地震稳定性分析研究评述[J].地震工程与工程振动,2005,25(1):164-171.LIU Hong-shuai,BO Jing-shan,LIU De-dong.Review on study of seismic stability analysis of rock-soil slopes[J].Earthquake Engineering and Engineering Vibration,2005,25(1):164-171.
[4]栾茂田,李湛,范庆林.土石坝拟静力稳定性分析与坝坡地震滑移量估算[J].岩土力学,2007,28(2):224-236.LUAN Mao-tian,LI Zhan,FAN Qing-lai.Analysis and evaluation of pseudo-static aseismic stability and seisminduced sliding movement of earth-rock dams[J].Rock and Soil Mechanics,2007,28(2):224-236.
[5]黄建梁,王威中,薛宏交.坡体地震稳定性的动态分析[J].地震工程与工程振动,1997,17(4):114-122.HUANG Jian-liang,WANG Wei-zhong,XUE Hong-jiao.Dynamic analysis of seismic stability of slopes[J].Earthquake Engineering and Engineering Vibration,1997,17(4):113-122.
[6]LING H I,LESHCHINSKY D,YOSHIYUKI M.Soil slopes under combined horizontal and vertical seismic accelerations[J].Earthquake Engineering and Structural Dynamics,1997,26(12):1231-1241.
[7]李红军,迟世春,钟红,等.考虑时程竖向加速度的Newmark滑块位移法[J].岩土力学,2007,28(11):2385-2390.LI Hong-jun,CHI Shi-chun,ZHONG Hong,et al.Effects of vertical acceleration time-histories on Newmark sliding block analyses[J].Rock and Soil Mechanics,2007,28(11):2385-2390.
[8]ROBERT SHUKHA,RAFAEL BAKER.Design implications of the vertical pseudo-static coefficient in slope analysis[J].Computers and Geotechnics,2008,35:86-96.
[9]ANDRZEJ SAWICKI,WLODZIMIERZ CHYBICKI,MAREK KULCZYKOWSKI.Influence of vertical ground motion on seismic-induced displacements of gravity structures[J].Computers and Geotechnics,2007,34:485-497.
[10]郑宏,田斌,刘德富,等.关于有限元边坡稳定性分析中安全系数的定义问题[J].岩石力学与工程学报,2005,24(13):2225-2230.ZHENG Hong,TIAN Bin,LIU De-fu,et al.On definitions of safety factor of slope stability analysis with finite elem ent method[J].Chinese Journal of Rock Mechanics and Engineering,2005,24(13):2225-2230.
[11]刘汉龙,费康,高玉峰.边坡地震稳定性时程分析方法[J].岩土力学,2003,24(4):553-556.LIU Han-long,FEI Kang,GAO Yu-feng.Time history analysis method of slope seismic stability[J].Rock and Soil Mechanics,2003,24(4):553-556.
[12]STAVROULA Kontoe,LIDIJA Zdravkovic,DAVID M Potts.An assessment of time integration schemes for dynamic geotechnical problems[J].Computers and Geotechnics,2008,35:253-264.
[13]中国水利水电科学研究院.DL5073-2000水工建筑物抗震设计规范[S].北京:中国电力出版社,2003.
[14]JOSEPH PENZIEN,MAKOTOWATABE.Characteristics of 3-dimensional earthquake ground motions[J].Earthquake Engineering and Structural Dynamics,1975,3:365-373.
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