正断层诱发砂土中群桩基础破坏及避让距离研究
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摘要
地震中发震断层诱发桩基失效,导致上部结构破坏甚至坍塌,相关破坏机制和避让距离缺乏系统研究。通过离心机试验和数值模拟,针对基岩正断层活动诱发上覆砂土中群桩基础的静力破坏展开研究,考察不同群桩断层相对位置下群桩的破坏特征。试验与计算结果均表明,当群桩跨越断层时,正断层活动使群桩向上盘一侧倾斜,并使基桩弯向上盘一侧。基桩桩顶荷载的重分布进一步使基桩形成受拉和受压两种破坏模式。数值参数分析表明,在不同桩位上,群桩的变形响应可划分为5个特征区域。对于埋深为20.0 m的基岩正断层,群桩在上盘和下盘一侧的安全避让距离分别为23.5 m和15.9 m,其中下盘一侧离开断层7.9 m至上盘一侧离开断层4.1 m的区域需要进行重点避让。
Pile foundation could be severely damaged by active fault during an earthquake, resulting damage and even collapse of superstructures. The pile failure mechanism and setback distance are not yet investigated systematically. Centrifuge and numerical modeling of pile group foundation in sand subjected to normal faulting were conducted. The influences of pile location relative to the bedrock fault on failure mechanism of pile group were investigated. Centrifuge and numerical results consistently show that when the pile group crosses the bedrock fault, the pile tilts to the hanging wall after faulting and is also bent to the hanging wall. Loading redistribution between piles results in two different failure patterns of tension and compression. Numerical parametric study of pile locations show that five characteristic zones could be classified based on different pile responses. For a soil stratum with thickness of20.0 m, the setback distances of pile group at the side of footwall and hanging wall are 15.9 m and 23.5 m, respectively. The area within 7.9 m to the fault line at the footwall and 4.1 m to the fault line at the hanging wall is the most critical setback zone.
Pile foundation could be severely damaged by active fault during an earthquake, resulting damage and even collapse of superstructures. The pile failure mechanism and setback distance are not yet investigated systematically. Centrifuge and numerical modeling of pile group foundation in sand subjected to normal faulting were conducted. The influences of pile location relative to the bedrock fault on failure mechanism of pile group were investigated. Centrifuge and numerical results consistently show that when the pile group crosses the bedrock fault, the pile tilts to the hanging wall after faulting and is also bent to the hanging wall. Loading redistribution between piles results in two different failure patterns of tension and compression. Numerical parametric study of pile locations show that five characteristic zones could be classified based on different pile responses. For a soil stratum with thickness of20.0 m, the setback distances of pile group at the side of footwall and hanging wall are 15.9 m and 23.5 m, respectively. The area within 7.9 m to the fault line at the footwall and 4.1 m to the fault line at the hanging wall is the most critical setback zone.
引文
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[18]ISHIHARA K.Liquefaction and flow failure during earthquakes[J].Geotechnique,1993,43(3):351-451.
[19]NG C W W,LU H.Effects of the construction sequence of twin tunnels at different depths on an existing pile[J].Canadian Geotechnical Journal,2014,51(2):173-183.
[20]SHI J W,WANG Y,CHEN Y H.A simplified method to estimate curvatures of continuous pipelines induced by normal fault movement[J].Canadian Geotechnical Journal,2017,55(3):343-352.
[21]Itasca Consulting Group.FLAC3D-Fast Lagrangian analysis of continua in 3 dimensions[M].Minnesota:Itasca Consulting Group,2012.
[22]CAI Q P,NG C W W.Analytical approach for estimating ground deformation profile induced by normal faulting in undrained clay[J].Canadian Geotechnical Journal,2013,50(4):413-422.
[23]骆冠勇,蔡奇鹏,吴宏伟.地层错动引起的上覆饱和黏土层变形特性的离心试验研究[J].岩土力学,2012,33(10):2985-2991.LUO Guan-yong,CAI Qi-peng,WU Hong-wei.Centrifuge modeling of ground deformations induced by normal fault in saturated clay[J].Rock and Soil Mechanics,2012,33(10):2985-2991.
[24]李赛,汪优,秦志浩,等.基于统计损伤本构模型的改进桩-土接触面模型研究[J].岩土力学,2016,37(7):1947-1955.LI Sai,WANG You,QIN Zhi-hao,et al.An improved constitutive model for pile-soil interface based on a statistical damage constitutive model[J].Rock and Soil Mechanics,2016,37(7):1947-1955.
[2]FACCIOLI E,ANASTASOPOULOS I,GAZETAS G,et al.Fault rupture-foundation interaction:selected case histories[J].Bulletin of Earthquake Engineering,2008,6(4):557-583.
[3]王东升,郭迅,孙治国,等.汶川大地震公路桥梁震害初步调查[J].地震工程与工程震动,2009,29(3):84-94.WANG Dong-sheng,GUO Xun,SUN Zhi-guo,et al.Damage to highway bridges during Wenchuan earthquake[J].Journal of Earthquake Engineering and Engineering Vibration,2009,29(3):84-94.
[4]杜修力,韩强,李忠献,等.5.12汶川地震中山区公路桥梁震害及启示[J].北京工业大学学报,2008,34(12):1270-1279.DU Xiu-li,HAN Qiang,LI Zhong-xian,et al.The seismic damage of bridges in the 2008 Wenchuan earthquake and lessons from its damage[J].Journal of Beijing University of Technology,2008,34(12):1270-1279.
[5]石玉玲,门玉明,彭建兵,等.地裂缝对不同结构形式桥梁桥面的破坏试验研究[J].岩土力学,2009,30(10):2917-2922.SHI Yu-ling,MEN Yu-ming,PENG Jian-bing,et al.Damage test study of different types structures of bridge decks by ground-fissure[J].Rock and Soil Mechanics,2009,30(10):2917-2922.
[6]LOLI M,BRANSBY M F,ANASTASOPOULOS I,et al.Interaction of caisson foundations with a seismically rupturing normal fault:centrifuge testing versus numerical simulation[J].Geotechnique,2012,62(1):29-43.
[7]ANASTASOPOULOS I,KOURKOULIS R,GAZETASG,et al.Interaction of piled foundation with rupturing normal fault[J].Geotechnique,2013,63(12):1042-1059.
[8]CAI Q P,Ng C W W.Centrifuge modeling of pile-sand interaction induced by normal faulting[J].Journal of Geotechnical and Geoenvironmental Engineering,ASCE,2016,142(10):04016046.
[9]徐锡伟,郭婷婷,刘少卓,等.活动断层避让相关问题的讨论[J].地震地质,2016,38(3):477-502.XU Xi-wei,GUO Ting-ting,LIU Shao-zhuo,et al.Discussion on issues associated with setback distance from active fault[J].Seismology and Geology,2016,38(3):477-502.
[10]蔡奇鹏,吴宏伟,陈星欣,等.正断层错动诱发单桩破坏及避让距离研究[J].岩土工程学报,2017,39(4):720-726.CAI Qi-peng,NG C W W,CHEN Xing-xin,et al.Failure mechanism and setback distance of single pile subjected to normal faulting[J].Chinese Journal of Geotechnical Engineering,2017,39(4):720-726.
[11]NG C W W,VAN LAAK P,TANG W H,et al.The Hong Kong geotechnical centrifuge[C]//Proceedings of 3rd International Conference of Soft Soil Engineering.Hong Kong:[s.n.],2001:225-230.
[12]蔡奇鹏,吴宏伟,胡平,等.隐伏裂缝对互层胶结土中正断层扩展影响研究[J].岩土力学,2017,38(7):2015-2021.CAI Qi-peng,NG C W W,HU Ping,et al.Effects of pre-existing fracture on propagation of normal fault ruptures in layered cemented soil[J].Rock and Soil Mechanics,2017,38(7):2015-2021.
[13]WHITE D J,TAKE W A,BOLTON M D.Soil deformation measurement using particle image velocimetry(PIV)and photogrammetry[J].Geotechnique,2003,53(7):619-631.
[14]FUGLSANG L D,OVESEN N K.The application of the theory of modeling to centrifuge studies[C]//Proceedings of International Conference of on Geotechnical Centrifuge Modeling.Rotterdam:Balkema,1988:119-138.
[15]ANASTASOPOULOS I,GAZETAS G,BRANSBY M F,et al.Fault rupture propagation through sand:finiteelement analysis and validation through centrifuge experiments[J].Journal of Geotechnical and Geoenvironmental Engineering,ASCE,2007,133(8):943-958.
[16]NG C W W,CAI Q P,HU P.Centrifuge and numerical modeling of normal fault-rupture propagation in clay with and without a preexisting fracture[J].Journal of Geotechnical and Geoenvironmental Engineering,ASCE,2012,138(12):1492-1502.
[17]CAI Q P,NG C W W.Effects of the tip depth of a pre-existing fracture on surface fault ruptures in cemented clay[J].Computers and Geotechnics,2014,56:181-190.
[18]ISHIHARA K.Liquefaction and flow failure during earthquakes[J].Geotechnique,1993,43(3):351-451.
[19]NG C W W,LU H.Effects of the construction sequence of twin tunnels at different depths on an existing pile[J].Canadian Geotechnical Journal,2014,51(2):173-183.
[20]SHI J W,WANG Y,CHEN Y H.A simplified method to estimate curvatures of continuous pipelines induced by normal fault movement[J].Canadian Geotechnical Journal,2017,55(3):343-352.
[21]Itasca Consulting Group.FLAC3D-Fast Lagrangian analysis of continua in 3 dimensions[M].Minnesota:Itasca Consulting Group,2012.
[22]CAI Q P,NG C W W.Analytical approach for estimating ground deformation profile induced by normal faulting in undrained clay[J].Canadian Geotechnical Journal,2013,50(4):413-422.
[23]骆冠勇,蔡奇鹏,吴宏伟.地层错动引起的上覆饱和黏土层变形特性的离心试验研究[J].岩土力学,2012,33(10):2985-2991.LUO Guan-yong,CAI Qi-peng,WU Hong-wei.Centrifuge modeling of ground deformations induced by normal fault in saturated clay[J].Rock and Soil Mechanics,2012,33(10):2985-2991.
[24]李赛,汪优,秦志浩,等.基于统计损伤本构模型的改进桩-土接触面模型研究[J].岩土力学,2016,37(7):1947-1955.LI Sai,WANG You,QIN Zhi-hao,et al.An improved constitutive model for pile-soil interface based on a statistical damage constitutive model[J].Rock and Soil Mechanics,2016,37(7):1947-1955.
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