考虑沉桩效应的群桩非线性荷载-沉降解析
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摘要
考虑沉桩效应对桩周土体力学特性的影响,采用指数函数型荷载传递曲线分别建立了静压桩的桩侧和桩端荷载传递模型。在此基础上,根据群桩加载过程中桩周土体的变形模式,基于荷载传递法描述桩-土界面的非线性行为,采用剪切位移法考虑群桩之间的相互作用,提出了考虑沉桩效应的群桩非线性荷载-沉降混合计算方法。通过开展离心模型试验对该计算方法解答进行了验证,研究了沉桩效应和桩-土界面非线性特征对群桩承载特性的影响。研究结果表明,沉桩效应对桩周土体起到挤密作用,使得桩周土体的强度和刚度增大,从而提高了群桩的承载特性。群桩加载过程中桩-土界面刚度随沉降变形而逐渐减小,使得群桩荷载-沉降曲线呈现出明显的非线性特征。
Considering the effects of the pile installation on the properties of the soils surrounding the piles, the load transfer models for pile shaft and pile base are established using the exponential function type load transfer curve. Then, according to the deformation mode of the soil around the piles, the stress transfer method is adopted to model the nonlinear behaviour at the pile-soil interface and the shear displacement method is used to evaluate the pile-pile interaction effects. A hybrid calculation method is proposed for assessing the nonlinear load-settlement behaviour of pile groups. The proposed method is verified by the centrifuge model test. Investigations are conducted on the effects of pile installation and nonlinear behaviour on bearing performance of pile groups. The results show that, the strength and stiffness of the soil around the piles are significantly enhanced by the pile installation due to the squeeze effects, which greatly improves the bearing performance of the pile group. The stiffness of pile-soil interface decreases with the increase of the settlement, and hence the pile group exhibits apparent nonlinear behaviour during the loading process.
Considering the effects of the pile installation on the properties of the soils surrounding the piles, the load transfer models for pile shaft and pile base are established using the exponential function type load transfer curve. Then, according to the deformation mode of the soil around the piles, the stress transfer method is adopted to model the nonlinear behaviour at the pile-soil interface and the shear displacement method is used to evaluate the pile-pile interaction effects. A hybrid calculation method is proposed for assessing the nonlinear load-settlement behaviour of pile groups. The proposed method is verified by the centrifuge model test. Investigations are conducted on the effects of pile installation and nonlinear behaviour on bearing performance of pile groups. The results show that, the strength and stiffness of the soil around the piles are significantly enhanced by the pile installation due to the squeeze effects, which greatly improves the bearing performance of the pile group. The stiffness of pile-soil interface decreases with the increase of the settlement, and hence the pile group exhibits apparent nonlinear behaviour during the loading process.
引文
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[11]MYLONAKIS G,GAZETAS G.Settlement and additional internal forces of grouped piles in layered soil[J].Géotechnique,1998,48(1):55-72.
[12]SAID I,DE G V,FRANK R.Axisymmetric finite element analysis of pile loading tests[J].Computers and Geotechnics,2009,36(1):6-19.
[13]杜家庆,杜守继,赵丹蕾,等.竖向荷载下群桩-土-承台相互作用数值分析[J].岩土力学,2013,34(8):2414-2420.DU Jia-qing,DU Shou-ji,ZHAO Dan-lei,et al.Numerical analysis of interaction of pile group-soil-raft under vertical load[J].Rock and Soil Mechanics,2013,34(8):2414-2420.
[14]张乾青,张忠苗.群桩沉降简化计算方法[J].岩土力学,2012,33(2):382-432.ZHANG Qian-qing,ZHANG Zhong-miao.A simplified calculation approach for settlement of pile groups[J].Rock and Soil Mechanics,2012,33(2):382-432.
[15]O'NEILL M W,HAWKINS R A,MAHAR L J,et al.Load transfer mechanism in piles and pile groups[J].Journal of Geotechnical and Geoenvironmental Engineering,1982,108(12):1605-1623.
[16]LEE K M,XIAO Z R.A simplified nonlinear approach for pile group settlement analysis in multilayered soils[J].Canadian Geotechnical Journal,2001,38(5):1063-1080.
[17]SHEN W Y,CHOW Y K,YONG K Y.A variational approach for the analysis of pile group-pile cap interaction[J].Géotechnique,2000,50(4):349-357.
[18]POULOS H G.Pile raft foundations design and applications[J].Géotechnique,2001,51(2):95-113.
[19]YANG M.Study on reducing-settlement pile foundation based on controlling settlement principle[J].Chinese Journal of Geotechnical Engineering,2000,22(4):481-486.
[20]SHEIL B B,MCCABE B A.An analytical approach for the prediction of single pile and pile group behaviour in clay[J].Computers and Geotechnics,2016,75:145-158.
[21]RANDOLPH M F,WROTH C P.Application of the failure state in undrained simple shear to the shaft capacity of driven piles[J].Géotechnique,1981,31(1):143-157.
[22]LI L,LI J P,SUN D A.Anisotropically elasto-plastic solution to undrained cylindrical cavity expansion in K0-consolidated clay[J].Computers and Geotechnics,2016,73(1):83-90.
[23]WOOD D M.Soil behaviour and critical state soil mechanics[M].Cambridge,UK:Cambridge University Press,1990.
[24]LEUNG Y F,SOGA K,LEHANE B M,et al.Role of linear elasticity in pile group analysis and load test interpretation[J].Journal of Geotechnical and Geoenvironmental Engineering,2010,136(12):1686-1694.
[25]COOKE R W,PRICE G,TARR K,et al.Jacked piles in London clay:Interaction and group behaviour under working conditions[J].Géotechnique,1980,30(2):97-136.
[26]ZHANG Q Q,LI S C,LIANG F Y,et al.Simplified method for settlement prediction of single pile and pile group using a hyperbolic model[J].International Journal of Civil Engineering,2014,12(2):146-156.
[27]中国建筑科学研究院.JGJ 106―2014建筑基桩检测技术规范[S].北京:中国建筑工业出版社,2014.China Academy of Building Research.JGJ 106―2014Technical code for testing of building foundation piles[S].Beijing:China Architecture&Building Press,2014.
[2]秋仁东,刘金砺,高文生,等.群桩基础沉降计算中的若干问题[J].岩土工程学报,2011,33(增刊2):15-23.QIU Ren-dong,LIU Jin-li,GAO Wen-sheng,et al.Some problems on settlement calculation of pile group foundation[J].Chinese Journal of Geotechnical Engineering,2011,33(Supp.2):15-23.
[3]赵明华,邹丹,邹新军.基于荷载传递法的高承台桩基沉降计算方法研究[J].岩石力学与工程学报,2005,24(13):2310-2314.ZHAO Ming-hua,ZOU Dan,ZOU Xin-jun.Settlement calculation of pile foundations with elevated caps by load transfer method[J].Chinese Journal of Rock Mechanics and Engineering,2005,24(13):2310-2314.
[4]CASTELLI F,MAUGERI M.Simplified nonlinear analysis for settlement prediction of pile groups[J].Journal of Geotechnical and Geoenvironmental Engineering,2002,128(1):76-84.
[5]LEE S,CHUNG C.An experimental study of the interaction of vertically loaded pile groups in sand[J].Canadian Geotechnical Journal,2005,42(5):1485-1493.
[6]SHEIL B B,MCCABE B A,HUNT C E,et al.A practical approach for the consideration of single pile and pile group installation effects in clay:Numerical modeling[J].Journal of Geo-Engineering Sciences,2015,2:119-42.
[7]MCCABE B A,LEHANE B M.Behavior of axially loaded pile groups driven in clayey silt[J].Journal of Geotechnical and Geoenvironmental Engineering,2006,132(3):401-410.
[8]LI L,LI J P,SUN D A,et al.Analysis of time-dependent bearing capacity of a driven pile in clayey soils by total stress method[J].International Journal of Geomechanics,2016,27(7).DOI:10.1061/(ASCE)GM.1943-5622.0000860.
[9]POULOS H G,DAVIS E H.Pile foundation analysis and design[M].New York:John Wiley and Sons,1980.
[10]RANDOLPH M F,WROTH C P.An analysis of the vertical deformation of pile groups[J].Géotechnique,1979,29(4):423-439.
[11]MYLONAKIS G,GAZETAS G.Settlement and additional internal forces of grouped piles in layered soil[J].Géotechnique,1998,48(1):55-72.
[12]SAID I,DE G V,FRANK R.Axisymmetric finite element analysis of pile loading tests[J].Computers and Geotechnics,2009,36(1):6-19.
[13]杜家庆,杜守继,赵丹蕾,等.竖向荷载下群桩-土-承台相互作用数值分析[J].岩土力学,2013,34(8):2414-2420.DU Jia-qing,DU Shou-ji,ZHAO Dan-lei,et al.Numerical analysis of interaction of pile group-soil-raft under vertical load[J].Rock and Soil Mechanics,2013,34(8):2414-2420.
[14]张乾青,张忠苗.群桩沉降简化计算方法[J].岩土力学,2012,33(2):382-432.ZHANG Qian-qing,ZHANG Zhong-miao.A simplified calculation approach for settlement of pile groups[J].Rock and Soil Mechanics,2012,33(2):382-432.
[15]O'NEILL M W,HAWKINS R A,MAHAR L J,et al.Load transfer mechanism in piles and pile groups[J].Journal of Geotechnical and Geoenvironmental Engineering,1982,108(12):1605-1623.
[16]LEE K M,XIAO Z R.A simplified nonlinear approach for pile group settlement analysis in multilayered soils[J].Canadian Geotechnical Journal,2001,38(5):1063-1080.
[17]SHEN W Y,CHOW Y K,YONG K Y.A variational approach for the analysis of pile group-pile cap interaction[J].Géotechnique,2000,50(4):349-357.
[18]POULOS H G.Pile raft foundations design and applications[J].Géotechnique,2001,51(2):95-113.
[19]YANG M.Study on reducing-settlement pile foundation based on controlling settlement principle[J].Chinese Journal of Geotechnical Engineering,2000,22(4):481-486.
[20]SHEIL B B,MCCABE B A.An analytical approach for the prediction of single pile and pile group behaviour in clay[J].Computers and Geotechnics,2016,75:145-158.
[21]RANDOLPH M F,WROTH C P.Application of the failure state in undrained simple shear to the shaft capacity of driven piles[J].Géotechnique,1981,31(1):143-157.
[22]LI L,LI J P,SUN D A.Anisotropically elasto-plastic solution to undrained cylindrical cavity expansion in K0-consolidated clay[J].Computers and Geotechnics,2016,73(1):83-90.
[23]WOOD D M.Soil behaviour and critical state soil mechanics[M].Cambridge,UK:Cambridge University Press,1990.
[24]LEUNG Y F,SOGA K,LEHANE B M,et al.Role of linear elasticity in pile group analysis and load test interpretation[J].Journal of Geotechnical and Geoenvironmental Engineering,2010,136(12):1686-1694.
[25]COOKE R W,PRICE G,TARR K,et al.Jacked piles in London clay:Interaction and group behaviour under working conditions[J].Géotechnique,1980,30(2):97-136.
[26]ZHANG Q Q,LI S C,LIANG F Y,et al.Simplified method for settlement prediction of single pile and pile group using a hyperbolic model[J].International Journal of Civil Engineering,2014,12(2):146-156.
[27]中国建筑科学研究院.JGJ 106―2014建筑基桩检测技术规范[S].北京:中国建筑工业出版社,2014.China Academy of Building Research.JGJ 106―2014Technical code for testing of building foundation piles[S].Beijing:China Architecture&Building Press,2014.