循环荷载作用下单桩动力模型试验与桩土界面特性研究
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摘要
通过开展红黏土中单桩轴向循环振动模型试验,研究不同循环荷载比和加载频率对桩长期动力特性的影响,从桩侧土剪切刚度和侧阻退化两方面出发,对循环荷载作用下桩顶累积沉降机制进行分析。在FLAC3D中,实现能够反映剪切刚度疲劳退化的修正Hardin-Drnevich(H-D)模型,并对常法向刚度(CNS)循环剪切下侧阻退化进行数值模拟。试验发现,循环荷载幅值是桩顶累积沉降变化的重要影响因素;桩顶动刚度在加载初期要先经历一个迅速降低的短暂过渡阶段,之后则不随振次的增加而改变;桩身振动在桩周土中引起的超孔压较小,有效应力的降低不足于使侧阻力发生较大程度的退化;随着加载速度的增大,桩顶动刚度和加速度均随之增大。采用修正H-D模型得到的理论滞回曲线与数值结果基本吻合,验证了程序编制的正确性。
The performance of small-scale model piles embedded into red clay and tested under cyclic axial loadings is presented in this paper.The influences of cyclic loading levels and rates on long-term dynamic behaviors of pile are observed,and the mechanics of accumulated settlement is analyzed from the views of shear stiffness softening and skin friction degradation.Furthermore,the modified Hardin-Drnevich(H-D) model,being capable of reflecting the fatigue degradation of shear stiffness,is achieved in the FLAC3D,and the behavior of shear resistance degradation during quasi-static cyclic shearing under constant normal stiffness(CNS) condition is numerically investigated.Results indicate that the growth pattern of the permanent deformation is significantly affected by the cyclic loading amplitude;and the pile dynamic stiffness experiences a significant decrease in a short transition period,after which it remains invariable with cycles.The excess pore pressure caused by the shaft vibration is rather small;and the induced effective stress reduction can not sufficiently result in large friction degradation.The dynamic stiffness and acceleration of pile top increase simultaneously with the loading rates.With the modified H-D model re-developed in FLAC3D,the hysteresis curve of an easy case is well consistent with the theoretical result,which verifies the credibility of the program.
The performance of small-scale model piles embedded into red clay and tested under cyclic axial loadings is presented in this paper.The influences of cyclic loading levels and rates on long-term dynamic behaviors of pile are observed,and the mechanics of accumulated settlement is analyzed from the views of shear stiffness softening and skin friction degradation.Furthermore,the modified Hardin-Drnevich(H-D) model,being capable of reflecting the fatigue degradation of shear stiffness,is achieved in the FLAC3D,and the behavior of shear resistance degradation during quasi-static cyclic shearing under constant normal stiffness(CNS) condition is numerically investigated.Results indicate that the growth pattern of the permanent deformation is significantly affected by the cyclic loading amplitude;and the pile dynamic stiffness experiences a significant decrease in a short transition period,after which it remains invariable with cycles.The excess pore pressure caused by the shaft vibration is rather small;and the induced effective stress reduction can not sufficiently result in large friction degradation.The dynamic stiffness and acceleration of pile top increase simultaneously with the loading rates.With the modified H-D model re-developed in FLAC3D,the hysteresis curve of an easy case is well consistent with the theoretical result,which verifies the credibility of the program.
引文
[1]杨龙才,郭庆海,周顺华,等.高速铁路桥桩在轴向循环荷载长期作用下的承载和变形特性试验研究[J].岩石力学与工程学报,2005,24(13):2362-2368.YANG Long-cai,GUO Qing-hai,ZHOU Shun-hua,et al.Dynamic behaviors of pile foundation of high-speedrailway bridge under long-term cyclic loading in softsoil[J].Chinese Journal of Rock Mechanics andEngineering,2005,24(13):2362-2368.
[2]朱斌,任宇,陈仁朋,等.竖向下压循环荷载作用下单桩承载力及累积沉降特性模型试验研究[J].岩土工程学报,2009,31(2):186-193.ZHU Bin,REN Yu,CHEN Ren-peng,et al.Model test onbearing capacity and accumulated settlement of singlepile subjected to axial cyclic loading[J].Chinese Journalof Geotechnical Engineering,2009,31(2):186-193.
[3]黄雨,柏炯,周国鸣,等.单向循环荷载作用下饱和砂土中单桩沉降模型试验研究[J].岩土工程学报,2009,31(9):1440-1444.HUANG Yu,BAI Jiong,ZHOU Guo-ming,et al.Modeltests on settlement of a single pile in saturated sand underunilateral cyclic loading[J].Chinese Journal ofGeotechnical Engineering,2009,31(9):1440-1444.
[4]冯大阔,张建民,侯文峻.三维加载条件下粗粒土与结构接触面力学特性的试验研究[J].地震工程与工程振动,2010,30(6):154-161.FENG Da-kuo,ZHANG Jian-min,HOU Wen-jun.Progressive test investigation on 3D behavior of gravelstructure interface[J].Journal of Earthquake Engi-neering and Engineering Vibration,2010,30(6):154-161.
[5]BRIAUD J L,TEXAS A M V,FELIO G Y.Analysis ofexisting cyclic vertical load tests for piles in clay[C]//Offshore Technology Conference.Houston:[s.n.],1986:31-34.
[6]SHELLEY E O.Direct shear tests on Mexico City claywith reference to friction pile behaviour[J].Geotechnicaland Geological Engineering,1995,13:1-16.
[7]YASUHARA K,HYDE A F L,TOYOTA N,et al.Cyclicstiffness of plastic silt with an initial drained shearstress[C]//Proc.Geotechnique Symp.on Pre-failureDeformation of Geomterials.London:Thomas TelfordLtd.,1998:373-382.
[8]YASUHARA K,MURAKAMI S,SONG B W.Postcyclicdegradation of strength and stiffness for low plasticitysilt[J].Journal of Geotechnical and GeoenvironmentalEngineering,ASCE,2003,129(8):756-769.
[9]DESAI C S,NAGARAJ B K.Modeling for cyclic normaland shear behavior of interfaces[J].Journal ofEngineering Mechanics,ASCE,1988,114(7):1191-1217.
[10]DAVID W A,RIADH H A D,HARRY G P.Estimation ofpile friction degradation from shearbox tests[J].Geotechnical Testing Journal,ASTM,1992,15(4):388-392.
[11]JASDN T D,MARK F R,DAVID J W.Interface loadtransfer degradation during cyclic loading:A microscaleinvestigation[J].Soils and Foundations,2003,43(4):81-93.
[12]JASDN T D,DAVID J W,MARK F R.Microscaleobservation and modeling of soil-structure interfacebehavior using particle image velocimetry[J].Soils andFoundations,2006,46(1):15-28.
[13]TEJCHMAN J,BAUER E.FE-modeling of shearresistance degradation in granular materials during cyclicshearing under CNS condition[J].Computers andGeotechnics,2009,36:249-263.
[14]TEJCHMAN J.Finite element investigations of granularmaterial behaviour during cyclic wall shearing under aconstant normal stiffness condition[J].CanadianGeotechnical Journal,2010,47:982-998.
[15]HARDIN B O,DRNEVICH V P.Shear modulus anddamping in soils:Design equations and curves[J].Journal of the Soil Mechanics and FoundationsDivision,ASCE,1972,98(SM7):667-692.
[16]郭晓霞,迟世春,林皋.基于热力学定律的土体动力Hardin-Drnevich模型再认识[J].岩土力学,2008,29(9):2335-2340.GUO Xiao-xia,CHI Shi-chun,LIN Gao.Recognition ofdynamic Hardin-Drnevich model for soils based ongeneralized thermodynamics[J].Rock and SoilMechanics,2008,29(9):2335-2340.
[17]蒋明镜,沈珠江.结构性黏土剪切带的微观分析[J].岩土工程学报,1998,2(2):102-108.JIANG Ming-jing,SHEN Zhu-jiang.Microscopicanalysis of shear band in structured clay[J].ChineseJournal of Geotechnical Engineering,1998,2(2):102-108.
[2]朱斌,任宇,陈仁朋,等.竖向下压循环荷载作用下单桩承载力及累积沉降特性模型试验研究[J].岩土工程学报,2009,31(2):186-193.ZHU Bin,REN Yu,CHEN Ren-peng,et al.Model test onbearing capacity and accumulated settlement of singlepile subjected to axial cyclic loading[J].Chinese Journalof Geotechnical Engineering,2009,31(2):186-193.
[3]黄雨,柏炯,周国鸣,等.单向循环荷载作用下饱和砂土中单桩沉降模型试验研究[J].岩土工程学报,2009,31(9):1440-1444.HUANG Yu,BAI Jiong,ZHOU Guo-ming,et al.Modeltests on settlement of a single pile in saturated sand underunilateral cyclic loading[J].Chinese Journal ofGeotechnical Engineering,2009,31(9):1440-1444.
[4]冯大阔,张建民,侯文峻.三维加载条件下粗粒土与结构接触面力学特性的试验研究[J].地震工程与工程振动,2010,30(6):154-161.FENG Da-kuo,ZHANG Jian-min,HOU Wen-jun.Progressive test investigation on 3D behavior of gravelstructure interface[J].Journal of Earthquake Engi-neering and Engineering Vibration,2010,30(6):154-161.
[5]BRIAUD J L,TEXAS A M V,FELIO G Y.Analysis ofexisting cyclic vertical load tests for piles in clay[C]//Offshore Technology Conference.Houston:[s.n.],1986:31-34.
[6]SHELLEY E O.Direct shear tests on Mexico City claywith reference to friction pile behaviour[J].Geotechnicaland Geological Engineering,1995,13:1-16.
[7]YASUHARA K,HYDE A F L,TOYOTA N,et al.Cyclicstiffness of plastic silt with an initial drained shearstress[C]//Proc.Geotechnique Symp.on Pre-failureDeformation of Geomterials.London:Thomas TelfordLtd.,1998:373-382.
[8]YASUHARA K,MURAKAMI S,SONG B W.Postcyclicdegradation of strength and stiffness for low plasticitysilt[J].Journal of Geotechnical and GeoenvironmentalEngineering,ASCE,2003,129(8):756-769.
[9]DESAI C S,NAGARAJ B K.Modeling for cyclic normaland shear behavior of interfaces[J].Journal ofEngineering Mechanics,ASCE,1988,114(7):1191-1217.
[10]DAVID W A,RIADH H A D,HARRY G P.Estimation ofpile friction degradation from shearbox tests[J].Geotechnical Testing Journal,ASTM,1992,15(4):388-392.
[11]JASDN T D,MARK F R,DAVID J W.Interface loadtransfer degradation during cyclic loading:A microscaleinvestigation[J].Soils and Foundations,2003,43(4):81-93.
[12]JASDN T D,DAVID J W,MARK F R.Microscaleobservation and modeling of soil-structure interfacebehavior using particle image velocimetry[J].Soils andFoundations,2006,46(1):15-28.
[13]TEJCHMAN J,BAUER E.FE-modeling of shearresistance degradation in granular materials during cyclicshearing under CNS condition[J].Computers andGeotechnics,2009,36:249-263.
[14]TEJCHMAN J.Finite element investigations of granularmaterial behaviour during cyclic wall shearing under aconstant normal stiffness condition[J].CanadianGeotechnical Journal,2010,47:982-998.
[15]HARDIN B O,DRNEVICH V P.Shear modulus anddamping in soils:Design equations and curves[J].Journal of the Soil Mechanics and FoundationsDivision,ASCE,1972,98(SM7):667-692.
[16]郭晓霞,迟世春,林皋.基于热力学定律的土体动力Hardin-Drnevich模型再认识[J].岩土力学,2008,29(9):2335-2340.GUO Xiao-xia,CHI Shi-chun,LIN Gao.Recognition ofdynamic Hardin-Drnevich model for soils based ongeneralized thermodynamics[J].Rock and SoilMechanics,2008,29(9):2335-2340.
[17]蒋明镜,沈珠江.结构性黏土剪切带的微观分析[J].岩土工程学报,1998,2(2):102-108.JIANG Ming-jing,SHEN Zhu-jiang.Microscopicanalysis of shear band in structured clay[J].ChineseJournal of Geotechnical Engineering,1998,2(2):102-108.
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