地层错动引起的上覆砂层变形特性的离心试验研究
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摘要
地层错动引起的基岩上覆土体变形对地表的建筑物、地下管线和隧道的安全带来潜在危险。为减小这种危险给人们的生命财产带来的损失,掌握地层错动引起的上覆土层的变形行为规律,通过土工离心试验,采用PIV图片测距技术,研究不同基岩错动量下竖向正断层错动造成的地表变形特点和断层裂缝在砂层中传播的规律。通过分析试验得到位移和应变场,得到以下几点认识:(1)不均匀沉降地表宽度(剪切区)并不随基岩错动位移的增大而线性增大,尤其在下盘,其宽度增大幅度很小;(2)基岩向下错动给上盘带来的干扰和破坏大于下盘;(3)裂缝传播整体传播方向偏于上盘。主裂缝的总体传播方向与断层平面的夹角约等于土体在土层平均围压下的剪胀角。当裂缝传至土体上部时,传播角会向上盘偏转而变大。
Ground deformation induced by fault rupture gives a potential threat to the safety of infrastructures,pipe line systems and tunnels.In this paper,two centrifugal tests with different bedrock faulting displacements were conducted to investigate the static permanent responses of a sandy soil overlaying an active normal fault with a dip angle of 90°.Emphasis was placed on the results of engineering concerns:(1) the range of the significant distortion zone;(2) the characteristics of the ground deformation;and(3) the fault rupture propagation pattern in soil.Through analysis of the displacement vector and the deviatoric strain obtained by geotechnical PIV technique,the following conclusions are drawn:(1) the range of significant distortion zone does not increase linearly as the increase in bedrock displacement,especially on the foot wall block;(2) the fault rupture brings more disturbance on the hanging wall side than on the foot wall block;and(3) the fault rupture propagates toward the hanging wall block in a bending line.The propagation angle of the principal fault rupture through soil equals the dilation angle of the soil under the mean confining pressure.When approaching the upper part of stratum,the rupture bends towards the hanging wall block with a larger angle.
Ground deformation induced by fault rupture gives a potential threat to the safety of infrastructures,pipe line systems and tunnels.In this paper,two centrifugal tests with different bedrock faulting displacements were conducted to investigate the static permanent responses of a sandy soil overlaying an active normal fault with a dip angle of 90°.Emphasis was placed on the results of engineering concerns:(1) the range of the significant distortion zone;(2) the characteristics of the ground deformation;and(3) the fault rupture propagation pattern in soil.Through analysis of the displacement vector and the deviatoric strain obtained by geotechnical PIV technique,the following conclusions are drawn:(1) the range of significant distortion zone does not increase linearly as the increase in bedrock displacement,especially on the foot wall block;(2) the fault rupture brings more disturbance on the hanging wall side than on the foot wall block;and(3) the fault rupture propagates toward the hanging wall block in a bending line.The propagation angle of the principal fault rupture through soil equals the dilation angle of the soil under the mean confining pressure.When approaching the upper part of stratum,the rupture bends towards the hanging wall block with a larger angle.
引文
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[2]COLE J D A,LADE P V.Influence zones in alluvium over dip-slip faults[J].Journal of Geotechnical Engineering,1984,110(5):599-615.
[3]LADE P V,COLE D A,CUMMINGS D.Multiple failure surfacesover dip-slip faults[J].Journal of Geotechnical Engineering,1984,110(5):616-627.
[4]郭恩栋,冯启民,薄景山,等.覆盖土层场地地震断裂试验[J].地震工程与工程振动,2001,21(3):145-149.(GUO Endong,FENG Qimin,BO Jingshan,et al.Seismic test of soil site ruptures under fault displacmenet[J].Earthquake Engineering and Engineering Vibration,2001,21(3):145-149.(in Chinese))
[5]刘学增,滨田政则.活断层破坏在土体中传播的试验研究[J].岩土工程学报,2004,26(3):425-427.(LIU Xuezeng,MASANORI H.Experiments on rupture propagation of active faults in soil[J].Chinese Journal of Geotechnical Engineering,2004,26(3):425-427.(in Chinese))
[6]BRAY J D,SEED R B,CLUFF L S,et al.Earthquake fault rupture propagation through soil[J].Journal of Geotechnical Engineering,ASCE,1994,120(3):543-61.
[7]ANASTASOPOULOS I,GAZETAS G,ASCE M,et al.Fault rupture propagation through sand:finite element analysis and validation through centrifuge experiments[J].Journal of Geotechnical and Geoenvironmental Engineering,2007,133(8):943-58.
[8]STONE K J L,MUIR W D.Effects of dilatancy and particle size observed in model tests on sand[J].Soils and Foundations,1992,32(4):43-57.
[9]COSTA YD,ZORNBERG JG,BUENO BS,et al.Failure mechanisms in sand over a deep active trapdoor[J].Journal of Geotechnical and Geoenvironmental Engineering,2009,135(11):1741-53.
[10]MUIR W D.Soil behaviour and critical state soil mechanics[M].Cambridge,UK:Cambridge University Press,1991.
[11]LEE J W,HAMADA M.An experimental study of earthquake fault rupture propagation through a sandy soil deposit[J].Structural Engineering/Earthquake Engineering,2005,22(1):1-13.
[12]ROTH W H,SCOTT R F,AUSTIN I.Centrifuge modelling of fault propagation through alluvial soils[J].Geophysical Research Letters,1981,8(6):561-64.
[13]SCHOFIELD A N.Cambridge geotechnical centrifuge operations[J].Geotechnique,1980,30(3):227-68.
[14]TAYLOR R N E.Geotechnical centrifuge technology glasgow[M].[S.l.]:Blackie Academic and Professional,1994.
[15]WHITE DJ,TAKE W A,BOLTON M D.Soil deformation measurement using particle image velocimetry(PIV)and photo-grammetry[J].Geotechnique,2003,53(7):619-631.
[16]JEWELl R A,WROTH C P.Direct shear tests on reinforced sand[J].Geotechnique,1987,37(1):53-68.
[17]MITCHELL J K,SOGA K.Fundamentals of soil behavior[M].3rd ed.New York:John Wiley and Sons Ltd.,2005.
[18]NG C W W,VAN LAAK P,TANG W H,et al.The Hong Kong geotechnical centrifuge[C]//Proceedings of the3rd Int.Conf.Soft Soil Engineering.Hong Kong:[s.n.],2001:225-230.
[19]ERSLEV E A.Trishear fault-propagation folding[J].Geology,1991,19(6):617-620.
[20]BRANSBY M F,DAVIES M C R,NAHAS A E.Centrifuge modelling of normal fault-foundation interaction[J].Bulletin of Earthquake Engineering,2008,6(4):1-21.
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