砂土中单桩水平循环累积变形特性模型试验
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摘要
针对典型的浅海风机大直径单桩基础,采用自主设计的水平循环加载装置,在砂土地基中完成了单桩模型试验,揭示了长期水平循环加载下单桩累积变形响应特征。试验结果表明,桩顶水平累积位移随循环次数的变化呈两阶段特征,循环加载短期效应大于长期效应;砂土密实度及循环加载路径对桩顶累积位移特征影响较大;不同初始条件下,单桩水平循环刚度随着循环次数的增大而不断增大;不同密实砂土中循环后单桩水平静承载力的变化与松密砂剪切硬软化机制不完全一致。基于经验公式法,对单桩水平循环累积位移预测模型进行了参数分析。与试验结果对比分析表明,该模型能较好地预测不同循环加载路径下单桩累积位移。
Large-diameter single pile foundation is a typical foundation type for offshore wind turbines. Model tests of large-diameter single pile are conducted using a simple mechanical load rig designed in-house in sand. The cumulative deformation response of a single pile under long-term lateral cyclic loading is discussed. The test results indicate that the cumulative displacement of the pile head presents two phase characteristics with number of cycles, and the short-term effect for lateral cyclic loading is greater than the long-term effect. Sand density and cyclic loading paths greatly influence the displacement characteristics of the pile head. The lateral secant stiffness of the pile head increases with cycling under different initial conditions. The change of horizontal static bearing capacity of single pile after cyclic loading in sands of different densities is not completely consistent with hard-soft mechanism for loose-dense sand subjected to shear. The prediction model parameters for lateral cyclic cumulative displacement of single pile are obtained by use of the empirical formula method. Comparison between the calculation results and the test results show that this model can effectively predict the cumulative displacement of single pile under different cyclic paths.
Large-diameter single pile foundation is a typical foundation type for offshore wind turbines. Model tests of large-diameter single pile are conducted using a simple mechanical load rig designed in-house in sand. The cumulative deformation response of a single pile under long-term lateral cyclic loading is discussed. The test results indicate that the cumulative displacement of the pile head presents two phase characteristics with number of cycles, and the short-term effect for lateral cyclic loading is greater than the long-term effect. Sand density and cyclic loading paths greatly influence the displacement characteristics of the pile head. The lateral secant stiffness of the pile head increases with cycling under different initial conditions. The change of horizontal static bearing capacity of single pile after cyclic loading in sands of different densities is not completely consistent with hard-soft mechanism for loose-dense sand subjected to shear. The prediction model parameters for lateral cyclic cumulative displacement of single pile are obtained by use of the empirical formula method. Comparison between the calculation results and the test results show that this model can effectively predict the cumulative displacement of single pile under different cyclic paths.
引文
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[2]ZHANG C R,WHITE D,RANDOLPH M.Centrifuge modeling of the cyclic lateral response of a rigid pile in soft clay[J].Journal of Geotechnical and Geoenvironmental Engineering,2011,137:717-729.
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[10]LONG J,VANNESTEV G.Effects of cyclic lateral loads on piles in sand[J].Journal of Geotechnical Engineering,1994,120(1):225-244.
[11]VERDURE L,GARNIER J,LEVACHER D.Lateral cyclic loading of single piles in sand[J].Journal of Physical Modelling in Geotechnics,2003(3):17-28.
[12]ROSQUOET F,THOREL L,GARNIER J,et al.Lateral cyclic loading of sand-installed piles[J].Soils and Foundations,2007,47(5):821-832.
[13]罗如平,李卫超,杨敏.水平循环荷载下海上大直径单桩累积变形特性[J].岩土力学,2016,37(增刊2):607-612.LUO Ru-ping,LI Wei-chao,YANG Min.Accumulated response of offshore large-diameter monopile under lateral cyclic loading[J].Rock and Soil Mechanics,2016,37(Suppl.2):607-612.
[14]黄茂松,俞剑,张勋,等.一种模拟长期循环加载的试验系统:中国,ZL 2014 1 0390397.X[P].2016-08-24.HUANG Mao-song,YU Jian,ZHANG Xun,et al.An apparatus for long-term cyclic loading:China,ZL 2014 1 0390397.X[P].2016-08-24.
[15]中华人民共和国国家标准编写组.GB/T 50123―1999土工试验方法标准[S].北京:中国计划出版社,1999.National Standard Compilation Group of the People’s Republic of China.GB/T 50123―1999 Standard for soil test method[S].Beijing:China Planning Press,1999.
[16]TOMLINSON M J.Pile design and construction practice[M].London:Viewpoint Publications,1977:222-236.
[17]TERZAGHI K.Evaluation of coefficient of subgrade reaction[J].Geotechnique,1955,5:297-326.
[18]张勋,黄茂松.水平循环荷载下砂土中沉井加桩基础累积变形特性[J].岩石力学与工程学报,2016,35(6):1256-1272.ZHANG Xun,HUANG Mao-song.Cumulative deformation of a caisson-piles composite foundation in sand subjected to cyclic lateral loading[J].Chinese Journal of Rock Mechanics and Engineering,2016,35(6):1256-1272.
[19]ZHU B,BYRNE B W,HOULSBY G T.Long-term lateral cyclic response of suction caisson foundations in sand[J].Journal of Geotechnical and Geoenvironmental Engineering,2013,139(1):73-83.
[20]张宏博.长期往复荷载作用下无黏性材料累积变形研究[D].上海:同济大学,2006.ZHANG Hong-bo.Long term cumulative deformation of cohesionless material induced by repeated loading[D].Shanghai:Tongji University,2006.
[2]ZHANG C R,WHITE D,RANDOLPH M.Centrifuge modeling of the cyclic lateral response of a rigid pile in soft clay[J].Journal of Geotechnical and Geoenvironmental Engineering,2011,137:717-729.
[3]王富强,荣冰,张嘎,等.水平循环荷载下风电机桩基础离心模型试验研究[J].岩土力学,2011,32(7):1926-1930.WANG Fu-qiang,RONG Bing,ZHANG Ga,et al.Centrifugal model test of pile foundation for wind power unit under cyclic lateral loading[J].Rock and Soil Mechanics,2011,32(7):1926-1930.
[4]朱斌,熊根,刘晋超,等.砂土中大直径单桩水平受荷离心模型试验[J].岩土工程学报,2013,35(10):1807-1815.ZHU Bin,XIONG Gen,LIU Jin-chao,et al.Centrifuge modelling of a large-diameter single pile under lateral loads in sand[J].Chinese Journal of Geotechnical Engineering,2013,35(10):1807-1815.
[5]LEBLANC C,HOULSBY G Y,BYRNE B W.Response of stiff piles in sand to long-term cyclic lateral loading[J].Geotechnique,2010,60(2):79-90.
[6]LIN S S,LIAO J C.Permanent strains of piles in sand due to cyclic lateral loads[J].Journal of Geotechnical and Geoenvironmental Engineering,1999,125(9):798-802.
[7]LESNY K,HINZ P.Investigation of monopile behavior under cyclic lateral loading[C]//Proceedings of the 6th International Conference on Offshore Site Investigation and Geotechnics.London:[s.n.],2007:383-390.
[8]陈仁朋,顾明,孔令刚,等.水平循环荷载下高桩基础受力性状模型试验研究[J].岩土工程学报,2012,34(11):1990-1996.CHEN Ren-peng,GU Ming,KONG Ling-gang,et al.Large-scale model tests on high-rise platform pile groups under cyclic lateral loads[J].Chinese Journal of Geotechnical Engineering,2012,34(11):1990-1996.
[9]LITTLE R L,BRIAUD J L.Full scale cyclic lateral load tests on six single piles in sand[R].Texas:Geotechnical Div.Texas A&M University,College Station,1988.
[10]LONG J,VANNESTEV G.Effects of cyclic lateral loads on piles in sand[J].Journal of Geotechnical Engineering,1994,120(1):225-244.
[11]VERDURE L,GARNIER J,LEVACHER D.Lateral cyclic loading of single piles in sand[J].Journal of Physical Modelling in Geotechnics,2003(3):17-28.
[12]ROSQUOET F,THOREL L,GARNIER J,et al.Lateral cyclic loading of sand-installed piles[J].Soils and Foundations,2007,47(5):821-832.
[13]罗如平,李卫超,杨敏.水平循环荷载下海上大直径单桩累积变形特性[J].岩土力学,2016,37(增刊2):607-612.LUO Ru-ping,LI Wei-chao,YANG Min.Accumulated response of offshore large-diameter monopile under lateral cyclic loading[J].Rock and Soil Mechanics,2016,37(Suppl.2):607-612.
[14]黄茂松,俞剑,张勋,等.一种模拟长期循环加载的试验系统:中国,ZL 2014 1 0390397.X[P].2016-08-24.HUANG Mao-song,YU Jian,ZHANG Xun,et al.An apparatus for long-term cyclic loading:China,ZL 2014 1 0390397.X[P].2016-08-24.
[15]中华人民共和国国家标准编写组.GB/T 50123―1999土工试验方法标准[S].北京:中国计划出版社,1999.National Standard Compilation Group of the People’s Republic of China.GB/T 50123―1999 Standard for soil test method[S].Beijing:China Planning Press,1999.
[16]TOMLINSON M J.Pile design and construction practice[M].London:Viewpoint Publications,1977:222-236.
[17]TERZAGHI K.Evaluation of coefficient of subgrade reaction[J].Geotechnique,1955,5:297-326.
[18]张勋,黄茂松.水平循环荷载下砂土中沉井加桩基础累积变形特性[J].岩石力学与工程学报,2016,35(6):1256-1272.ZHANG Xun,HUANG Mao-song.Cumulative deformation of a caisson-piles composite foundation in sand subjected to cyclic lateral loading[J].Chinese Journal of Rock Mechanics and Engineering,2016,35(6):1256-1272.
[19]ZHU B,BYRNE B W,HOULSBY G T.Long-term lateral cyclic response of suction caisson foundations in sand[J].Journal of Geotechnical and Geoenvironmental Engineering,2013,139(1):73-83.
[20]张宏博.长期往复荷载作用下无黏性材料累积变形研究[D].上海:同济大学,2006.ZHANG Hong-bo.Long term cumulative deformation of cohesionless material induced by repeated loading[D].Shanghai:Tongji University,2006.