可液化土-高层结构振动台试验的土性参数识别
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摘要
基于已进行的可液化地基-桩-高层结构振动台试验,利用参数识别技术对试验记录的土体加速度和孔隙水压力进行分析,研究场地液化机制及土的动力特性。由振动台试验的土体加速度记录,通过剪切梁模型,求出土体的动剪切应力-剪切应变曲线,研究土体的动剪切模量及阻尼特性随动剪切应变的变化关系,并进一步研究土体剪切波速、有效应力路径及桩和土的剪切应变等情况。结果表明:在较强地震激励下,动剪切应力和动剪切应变滞回圈更饱满,表现出更强的滞回特性;土的刚度随着深度的增加而增大;孔压比存在明显的上升,孔隙水压力增长对土的剪切波速有影响,土的刚度随着孔隙水压力的上升而降低;利用参数识别技术得到的土的刚度与土动力性质试验得到的结果比较一致,而阻尼要高于土动力性质试验的结果;群桩内外土体的剪切应变形状相似,外侧土体的剪切应变比内侧土体的剪切应变大。该土性参数识别技术对于研究液化场地及液化场地中结构的抗震设计具有一定的参考价值。
Based on the shaking table tests on liquefiable soil-high-rise buildings interaction system,the site liquefaction mechanism and dynamic characteristics of liquefiable soil during earthquake excitation were analyzed by using parameter identification technique to study the acceleration and water pore pressure records.The time-history curves of cyclic shear stress and shear strain in the soils were evaluated from the acceleration records in the soil by one-dimensional shear beam model.These time-history curves were used to estimate variation in dynamic shear modulus of soil and material damping characteristics with shear strain amplitude.Shear wave velocity,effective stress path and shear strain of pile and soil were discussed further.The analysis result shows that:Under the stronger earthquake excitation,the soil stiffness increases with the increasing depth;the stress-strain loops are rounded and show larger hysteretic damping characteristics for large earthquake excitation;the ratio of pore water pressure to vertical effective consolidation pressure goes up obviously;the increasing pore water pressure has influence on shear wave of soil;soil stiffness and shear strength both decrease with the increase in pore water pressure.Soil stiffness calculated from measured accelerations is consistent with that obtained through independent laboratory tests;but the material damping calculated from measured accelerations is much larger than that measured in laboratory tests,which is smaller than the equivalent damping associated with hysteretic damping.The shear strains in the soils inside and outside the pile group were found to be compatible.However,the amplitude of the shear strain outside the pile group is larger than that inside the pile group.The parameter identification technique of soil properties is useful for studying liquefaction field and practical seismic design of structure in liquefaction field.
Based on the shaking table tests on liquefiable soil-high-rise buildings interaction system,the site liquefaction mechanism and dynamic characteristics of liquefiable soil during earthquake excitation were analyzed by using parameter identification technique to study the acceleration and water pore pressure records.The time-history curves of cyclic shear stress and shear strain in the soils were evaluated from the acceleration records in the soil by one-dimensional shear beam model.These time-history curves were used to estimate variation in dynamic shear modulus of soil and material damping characteristics with shear strain amplitude.Shear wave velocity,effective stress path and shear strain of pile and soil were discussed further.The analysis result shows that:Under the stronger earthquake excitation,the soil stiffness increases with the increasing depth;the stress-strain loops are rounded and show larger hysteretic damping characteristics for large earthquake excitation;the ratio of pore water pressure to vertical effective consolidation pressure goes up obviously;the increasing pore water pressure has influence on shear wave of soil;soil stiffness and shear strength both decrease with the increase in pore water pressure.Soil stiffness calculated from measured accelerations is consistent with that obtained through independent laboratory tests;but the material damping calculated from measured accelerations is much larger than that measured in laboratory tests,which is smaller than the equivalent damping associated with hysteretic damping.The shear strains in the soils inside and outside the pile group were found to be compatible.However,the amplitude of the shear strain outside the pile group is larger than that inside the pile group.The parameter identification technique of soil properties is useful for studying liquefaction field and practical seismic design of structure in liquefaction field.
引文
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[10]LI P Z,REN H M,LU X L,et al.Shaking table tests of dynamic interaction of soil-structure considering soil liquefaction[C]//Proceedings of the 14th World Conference on Earthquake Engineering.Beijing:[s.n.],2008:04-01-0024.
[11]KOGA Y,MATSUO O.Shaking table tests of embankments resting on liquefiable sandy ground[J].Soils and Foundations,1990,30(4):162-174.
[12]ELGAMAL A W,ZEGHAL M,TANG H T,et al.Evaluation of low-strain site characteristics using the Lotung seismic array[J].Journal of Geotechnical Engineering Division,ASCE,1995,121(4):350-362.
[13]ELGAMAL A W,YANG Z H,LAI T,et al.Dynamic response of saturated dense sand in laminated centrifuge container[J].Journal of Geotechnical and Geoenvironmental Engineering,ASCE,2005,131(5):598-609.
[14]RAYHANI M H T,NAGGAR M H E.Centrifuge modeling of seismic response of layered soft clay[J].Bulletin of Earthquake Engineering,2007,5(4):571-589.
[15]ZEGHAL M,ABDEL-GHAFFAR A M.Evaluation of the nonlinear seismic response of an earth dam:nonparametric system identification[J].Journal of Earthquake Engineering,2009,13(3):384-405.
[16]COX B R,STOKOE K H,RATHJE E M.An in situ test method for evaluating the coupled pore pressure generation and nonlinear shear modulus behavior of liquefiable soils[J].Geotechnical Testing Journal,2009,32(1):11-12.
[17]苏栋,李相菘.地震作用下自由场中饱和砂土的应力-应变推导[J].岩土力学,2010,31(1):277-281.(SUN Dong,LI Xiangsong.Derivation of stress and strain of saturated sand in free ground under seismic loading[J].Rock and Soil Mechanics,2010,31(1):277-281.(in Chinese))
[18]ZEGHAL M,ELGAMAL A W,PARRA E.Identification and modeling of earthquake ground response:II.site liquefaction[J].Soil Dynamics and Earthquake Engineering,1996,15(8):523-547.
[19]IWAN W D.On a class of models for the yielding behavior of continuous and composite systems[J].Journal of Applied Mechanics,ASME,1967,34(3):612-617.
[20]MRóZ Z.On the description of anisotropic work hardening[J].Journal of Mechanics and Physics of Solids,1967,15(3):163-175.
[21]ZEGHAL M,KALLOU P V,OSKAY C,et al.Identification and imaging of soil and soil-pile deformation in the presence of liquefaction[J].Earthquake Engineering and Engineering Vibration,2006,5(2),171-182.
[2]ZEGHAL M,ELGAMAL A W.Analysis of site liquefaction using earthquake records[J].Journal of Geotechnical Engineering Division,ASCE,1994,120(6):996-1 017.
[3]TAMURA S,SUZUKI Y,TSUCHIYA T,et al.Dynamic response and failure mechanisms of a pile foundation during soil liquefaction by shaking table test with a large-scale laminar shear box[C]//Proceedings of the 12th World Conference on Earthquake Engineering.Auckland:[s.n.],2000:903.
[4]KAGAWA T,MINOWA C,ABE A.EDUS project(earthquake damage to underground structures)[C]//Proceedings of the 12th World Conference on Earthquake Engineering.Auckland:[s.n.],2000:329.
[5]SUZUKI H,TOKIMATSU K,SATO M,et al.Soil-pile-structure interaction in liquefiable ground through multi-dimensional shaking table tests using E-defense facility[C]//Proceedings of the 14th World Conference on Earthquake Engineering.Beijing:[s.n.],2008:177.
[6]陈跃庆,吕西林,侯建国,等.有建筑物存在的软土地基液化模拟地震振动台试验研究[J].武汉大学学报:工学版,2003,36(1):59-64.(CHEN Yueqing,LU Xilin,HOU Jianguo,et al.Shaking table testing on seismic liquefaction of soft soil under building footing[J].Engineering Journal of Wuhan University,2003,36(1):59-64.(in Chinese))
[7]凌贤长,郭明珠,王东升,等.液化场地桩基桥梁震害响应大型振动台模型试验研究[J].岩土力学,2006,27(1):7-10.(LING Xianzhang,GUO Mingzhu,WANG Dongsheng,et al.Large-scale shaking table model test of seismic response of bridge of pile foundation in ground of liquefaction[J].Rock and Soil Mechanics,2006,27(1):7-10.(in Chinese))
[8]孟上九,刘汉龙,袁晓铭,等.可液化地基上建筑物不均匀震陷机制的振动台试验研究[J].岩石力学与工程学报,2005,24(11):1 978-1 985.(MENG Shangjiu,LIU Hanlong,YUAN Xiaoming,et al.Experimental study on the mechanism of earthquake-induced differential settlement of building on liquescent subsoil[J].Chinese Journal of Rock Mechanics and Engineering,2005,24(11):1 978-1 985.(in Chinese))
[9]冯士伦,王建华,郭金童.液化土层中桩基抗震性能振动台试验研究[J].土木工程学报,2005,38(7):92-95.(FENG Shilun,WANG Jianhua,GUO Jintong.Shaking table test on the seismic resistance of pile foundation in liquefied soil[J].China Civil Engineering Journal,2005,38(7):92-95.(in Chinese))
[10]LI P Z,REN H M,LU X L,et al.Shaking table tests of dynamic interaction of soil-structure considering soil liquefaction[C]//Proceedings of the 14th World Conference on Earthquake Engineering.Beijing:[s.n.],2008:04-01-0024.
[11]KOGA Y,MATSUO O.Shaking table tests of embankments resting on liquefiable sandy ground[J].Soils and Foundations,1990,30(4):162-174.
[12]ELGAMAL A W,ZEGHAL M,TANG H T,et al.Evaluation of low-strain site characteristics using the Lotung seismic array[J].Journal of Geotechnical Engineering Division,ASCE,1995,121(4):350-362.
[13]ELGAMAL A W,YANG Z H,LAI T,et al.Dynamic response of saturated dense sand in laminated centrifuge container[J].Journal of Geotechnical and Geoenvironmental Engineering,ASCE,2005,131(5):598-609.
[14]RAYHANI M H T,NAGGAR M H E.Centrifuge modeling of seismic response of layered soft clay[J].Bulletin of Earthquake Engineering,2007,5(4):571-589.
[15]ZEGHAL M,ABDEL-GHAFFAR A M.Evaluation of the nonlinear seismic response of an earth dam:nonparametric system identification[J].Journal of Earthquake Engineering,2009,13(3):384-405.
[16]COX B R,STOKOE K H,RATHJE E M.An in situ test method for evaluating the coupled pore pressure generation and nonlinear shear modulus behavior of liquefiable soils[J].Geotechnical Testing Journal,2009,32(1):11-12.
[17]苏栋,李相菘.地震作用下自由场中饱和砂土的应力-应变推导[J].岩土力学,2010,31(1):277-281.(SUN Dong,LI Xiangsong.Derivation of stress and strain of saturated sand in free ground under seismic loading[J].Rock and Soil Mechanics,2010,31(1):277-281.(in Chinese))
[18]ZEGHAL M,ELGAMAL A W,PARRA E.Identification and modeling of earthquake ground response:II.site liquefaction[J].Soil Dynamics and Earthquake Engineering,1996,15(8):523-547.
[19]IWAN W D.On a class of models for the yielding behavior of continuous and composite systems[J].Journal of Applied Mechanics,ASME,1967,34(3):612-617.
[20]MRóZ Z.On the description of anisotropic work hardening[J].Journal of Mechanics and Physics of Solids,1967,15(3):163-175.
[21]ZEGHAL M,KALLOU P V,OSKAY C,et al.Identification and imaging of soil and soil-pile deformation in the presence of liquefaction[J].Earthquake Engineering and Engineering Vibration,2006,5(2),171-182.
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