地震作用下裂隙对岩质边坡稳定性影响分析
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摘要
在地震作用下岩质边坡内部裂隙可能开裂扩展,对边坡稳定造成不利影响。利用扩展有限元法模拟岩质边坡内部裂隙在地震作用下的开裂扩展,根据扩展后的裂隙分析边坡潜在滑面,采用矢量和法计算边坡在震前、地震过程及震后的安全系数。结果表明:在汶川地震波作用下LLT1与LLT2裂隙均开裂扩展,开裂方向与水平方向夹角近45°,其中LLT1裂隙顶部开裂至边坡面。震前安全系数为1.75,地震过程中最小安全系数为1.01,震后安全系数为1.05。说明了即便是边坡在震前稳定性较好,但由于地震作用使得裂隙扩展贯通至边坡表面,导致滑体抗滑力降低,边坡震后稳定性显著降低。虽然地震过程中边坡并未失稳破坏,若在震后受到其他外部作用则可能失稳破坏,引发次生灾害。
Internal crack in rock slope may grow under seismic loading, which would have an adverse effect on slope stability. By taking advantage of extended finite element method(XFEM), the development of cracks in a rock slope located in the southwest China under seismic loading is simulated. An analysis of the potential sliding surface is carried out according to the crack after extension, and the factors of safety are calculated with vector sum analysis method(VSAM) before, during and after earthquake. The result shows, under the loading of Wenchuan seismic waves, both crack LLT1 and crack LLT2 grow. The angle between growth-direction and the horizontal is nearly 45 degree, and the crack LLT1 grows to the slope surface. The factors of safety before and after earthquake are 1.75 and 1.05 respectively, and the minimum factor of safety during the earthquake is 1.01. This illustrates that the slope is stable before earthquake, but the anti-sliding force and the slope stability are both reduced because of the growth of crack under the seismic loading. Even if the slope is stable in the process of the earthquake, it may collapse subjected to other forces after earthquake.
Internal crack in rock slope may grow under seismic loading, which would have an adverse effect on slope stability. By taking advantage of extended finite element method(XFEM), the development of cracks in a rock slope located in the southwest China under seismic loading is simulated. An analysis of the potential sliding surface is carried out according to the crack after extension, and the factors of safety are calculated with vector sum analysis method(VSAM) before, during and after earthquake. The result shows, under the loading of Wenchuan seismic waves, both crack LLT1 and crack LLT2 grow. The angle between growth-direction and the horizontal is nearly 45 degree, and the crack LLT1 grows to the slope surface. The factors of safety before and after earthquake are 1.75 and 1.05 respectively, and the minimum factor of safety during the earthquake is 1.01. This illustrates that the slope is stable before earthquake, but the anti-sliding force and the slope stability are both reduced because of the growth of crack under the seismic loading. Even if the slope is stable in the process of the earthquake, it may collapse subjected to other forces after earthquake.
引文
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[18]郭明伟,葛修润,李春光,等.关于矢量和分析方法中整体下滑趋势方向的研究[J].岩土工程学报,2009,31(4):577-583.GUO Ming-wei,GE Xiu-run,LI Chun-guang,et al.Study on potential sliding in slope stability analysis based on vector sum method[J].Chinese Journal of Geotechnical Engineering,2009,31(4):577-583.
[19]李录贤,国松直,王爱琴.无限元方法及其应用[J].力学进展,2007,(2):161-174.LI Lu-xian,KUNIMATSU S,WANG Ai-qin.The infinite element method and its application[J].Advances in Mechanics,2007,37(2):161-174.
[20]HOEK E,BRAY J.Rock slope engineering[M].[S.l.]:Institution of Mining and Metallurgy,1981.
[21]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.
[2]NEWMARK N M.Effects of earthquakes on dams and embankments[J].Geotechnique,1965,15(2):139-160.
[3]薄景山,徐国栋,景立平.土边坡地震反应及其动力稳定性分析[J].地震工程与工程振动,2001,21(2):116-120.BO Jing-shan,XU Guo-dong,JING Li-ping.Seismic response and dynamic stability analysis of soil slopes[J].Earthquake Engineering and Engineering Vibration,2001,21(2):116-120.
[4]罗刚,胡卸文,顾成壮.强震作用下顺层岩质斜坡动力失稳机制及启动速度研究[J].岩土力学,2013,34(2):483-490.LUO Gang,HU Xie-wen,GU Cheng-zhuang.Study of kinetic failure mechanism and starting velocity of consequent rock slopes under strong earthquake[J].Rock and Soil Mechanics,2013,34(2):483-490.
[5]ZHANG C H,PEKAU O A,JIN F,et al.Application of distinct element method in dynamic analysis of high rockslopes and blocky structures[J].Soil Dynamics and Earthquake Engineering,1997,16(6):385-394.
[6]李忠生.国内外地震滑坡灾害研究综述[J].灾害学,2003,18(4):64-70.LI Zhong-sheng.The state of the art of the research on seismic landslide hazard at home and abroad[J].Journal of Catastrophology,2003,18(4):64-70.
[7]WANG F W,CHENG Q G,LYNN H,et al.Preliminary investigation of some large landslides triggered by Wenchuan earthquake in 2008,Sichuan Province,China[J].Landslides,2009,6(1):47-54.
[8]LI X P,SIMING H E.Seismically induced slope instabilities and the corresponding treatments:The case of a road in the Wenchuan earthquake hit region[J].Journal of Mountain Science,2009,6(1):96-100.
[9]许强,黄润秋.5.12汶川大地震诱发大型崩滑灾害动力特征初探[J].工程地质学报,2008,16(6):721-729.XU Qiang,HUANG Run-qiu.Kinetics characteristics of large landslides triggered by May 12th Wenchuan earthquake[J].Journal of Engineering Geology,2008,16(6):721-729.
[10]BELYTSCHKO T,BLACK T.Elastic crack growth in finite elements with minimal remeshing[J].International Journal for Numerical Methods in Engineering,1999,(45):601-620.
[11]郑安兴,罗先启,沈辉.危岩主控结构面变形破坏的扩展有限元模拟分析[J].岩土力学,2013,34(8):2371-2376.ZHENG An-xing,LUO Xian-qi,SHEN Hui.Numerical simulation and analysis of deformation and failure of jointed rock slopes by extended finite element method[J].Rock and Soil Mechanics,2013,34(8):2371-2376.
[12]MOS N,DOLBOW J,BELYTSCHKO T.A finite element method for crack growth without remeshing[J].International Journal for Numerical Methods in Engineering,1999,(46):131-150.
[13]DAUX C,MOS N,DOLBOW J,et al.Arbitrary branched and intersecting cracks with the extended finite element method[J].International Journal for Numerical Methods in Engineering,2000,48:1741-1760.
[14]STAZI F L,BUDYN E,CHESSA J,et al.An extendedfinite element method with higher-order elements for curved cracks[J].Computational Mechanics,2003,31:38-48.
[15]葛修润.用PC型微机对岩体工程课题进行有限元分析[C]//第一届全国计算岩土力学研讨会论文集.成都:西南交通大学出版社,1987:74-85.
[16]刘艳章,葛修润,李春光,等.基于矢量法安全系数的边坡与坝基稳定分析[J].岩石力学与工程学报,2007,26(10):2130-2140.LIU Yan-zhang,GE Xiu-run,LI Chun-guang,et al.Stability analysis of slope and dam foundation based on vector method safety factor[J].Chinese Journal of Rock Mechanics and Engineering,2007,26(10):2130-2140.
[17]葛修润.岩石疲劳破坏的变形控制律、岩土力学试验的实时X射线CT扫描和边坡坝基抗滑稳定分析的新方法[J].岩土工程学报,2008,30(1):1-20.GE Xiu-run.Deformation control law of rock fatigue failure,real-time X-ray CT scanning of geotechnical testing,and new method of stability analysis of slopes and dam foundations[J].Chinese Journal of Geotechnical Engineering,2008,30(1):1-20.
[18]郭明伟,葛修润,李春光,等.关于矢量和分析方法中整体下滑趋势方向的研究[J].岩土工程学报,2009,31(4):577-583.GUO Ming-wei,GE Xiu-run,LI Chun-guang,et al.Study on potential sliding in slope stability analysis based on vector sum method[J].Chinese Journal of Geotechnical Engineering,2009,31(4):577-583.
[19]李录贤,国松直,王爱琴.无限元方法及其应用[J].力学进展,2007,(2):161-174.LI Lu-xian,KUNIMATSU S,WANG Ai-qin.The infinite element method and its application[J].Advances in Mechanics,2007,37(2):161-174.
[20]HOEK E,BRAY J.Rock slope engineering[M].[S.l.]:Institution of Mining and Metallurgy,1981.
[21]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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