可液化砂土中群桩基础地震响应的振动台试验研究
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摘要
为研究可液化砂土地基中桩基体系在地震力作用下的动力特性,进行室内振动台天然地基、3D、3.5D、4D桩间距桩基加固地基四种工况模型试验。通过布设传感器对各工况下特定深度的初始有效应力、振动过程中超静孔隙水压力时程、沉降时程进行测定,对桩基加固地基振动前后竖向承载力进行分析。结果表明,桩基加固后的地基土发生液化滞后于天然地基,且桩间距为3D、3.5D的加固地基提高抗液化强度较明显。随桩间距的加大,提高程度会减弱;据不同工况振动过程中发生的最大沉降量,3D桩间距加固的桩基竖向动承载力较高;模拟地震力振动达稳定后桩基的竖向承载力均高于振动前同工况竖向承载力。试验分析可对饱和砂土在地震力作用下PSSI效应进一步理解,为桩基优化设计提供参考。
In order to study dynamic characteristics of a pile foundation with liquefiable sandy soil under seismic loading,the four working conditions were studied including natural foundation,pile foundations with 3D,3.5D and 4D(D is the pile diameter) pile spaces by means of indoor shaking table model test.Initial effective stresses,time histories of excess pore water pressure and time histories of settlement during vibrations were determined with sensors.At the same time,the vertical bearing capacities of the pile reinforced foundations after vibrations were compared with those before vibrations.The test results showed that the liquefaction of soil for pile reinforced foundations delays compared with that of the natural foundation,and the pile foundations with 3D and 3.5D can more significantly improve liquefaction resistance;the vertical dynamic bearing capacity of the pile foundation with 3D is higher according to the largest settlement during vibration;all the vertical bearing capacities of pile foundations become larger after vibration.Based on the test,the pilesoil-structure dynamic interaction was understood more deeply during liquefaction of soil.The results provided a reference for optimal design of pile foundations.
In order to study dynamic characteristics of a pile foundation with liquefiable sandy soil under seismic loading,the four working conditions were studied including natural foundation,pile foundations with 3D,3.5D and 4D(D is the pile diameter) pile spaces by means of indoor shaking table model test.Initial effective stresses,time histories of excess pore water pressure and time histories of settlement during vibrations were determined with sensors.At the same time,the vertical bearing capacities of the pile reinforced foundations after vibrations were compared with those before vibrations.The test results showed that the liquefaction of soil for pile reinforced foundations delays compared with that of the natural foundation,and the pile foundations with 3D and 3.5D can more significantly improve liquefaction resistance;the vertical dynamic bearing capacity of the pile foundation with 3D is higher according to the largest settlement during vibration;all the vertical bearing capacities of pile foundations become larger after vibration.Based on the test,the pilesoil-structure dynamic interaction was understood more deeply during liquefaction of soil.The results provided a reference for optimal design of pile foundations.
引文
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[2]Chacko M,Thesis M S.Analysis of dynamic soil-pile-structure interaction[M].Univ.of California,Davis,1995.
[3]Makris N,Tazoh T,Yun X,et al.Prediction of the measured response of a scaled soil-pile-superstructure system[J].Soil Dyn.Earthquake Eng.,1997,16(2):113-124.
[4]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].Proc.,of 12th World Conf.on Earthq.Engrg.,Reference,2000:903.
[5]Tamura S,Minowa C,Tokimastu K,et al.Evaluation of earth pressure acting on embedded pile-cap based on liquefaction test using larger-scale shaking table[M].Japan National Conf.on Geotech.Engrg,2002.
[6]王建华,冯士伦.桩土相互作用的振动台试验研究[J].岩土工程学报,2004,26(5):616-618.WANG Jian-hua,FENG Shi-lun.The shake table test on soilpile interaction[J].Chinese Journal of Geotechnical Engineering,2004,26(5):616-618.
[7]王建华,冯士伦.液化土层中桩基水平承载特性分析[J].岩土力学,2005,26(10):1597-1601.WANG Jian-hua,FENG Shi-lun.Research on lateral resistance of pile foundation in liquefaction strata[J].Rock and Soil Mechanics,2005,26(10):1597-1601.
[8]刘立平.水平地震作用下桩-土-上部结构弹塑性动力相互作用分析[D].重庆:重庆大学,2004.
[9]冯士伦.可液化土层中桩基横向承载特性研究[D].天津:天津大学,2004.
[10]余俊.饱和土地基-桩基-上部结构动力相互作用理论分析与试验研究[D].长沙:湖南大学,2007.
[11]卢华喜.成层地基-桩基-上部结构动力相互作用理论分析与试验研究[D].长沙:湖南大学,2006.
[12]陆建飞,聂卫东.饱和土中单桩在瑞利波作用下的动力响应[J].岩土工程学报,2008,30(2):225-231.LU Jian-fei,NIE Wei-dong.Dynamic response of single pile embedded in half-space saturated soil subjected to rayleigh waves[J].Chinese Journal of Geotechnical Engineering,2008,30(2):225-231.
[13]陈跃庆.结构-地基动力相互作用体系振动台试验研究[D].上海:同济大学,2001.
[14]黄占芳,王显耀,吴植安,等.可液化砂土中单桩地震响应的振动台试验研究[J].振动与冲击,2012,31(20):189-192.HUANG Zhan-fang,WU Xian-yao,WU Zhi-an,et al.Shaking table tests for single pile-soil dynamic interaction in liquefied foundation soil[J].Journal of Vibration and Shock,2012,31(20):189-192.
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