砂土中大直径单桩水平受荷离心模型试验
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摘要
大直径桩基在海洋工程中已越来越广泛应用。针对目前API规范p–y曲线对水平受荷大直径单桩的不适用性,通过离心模型试验研究了砂性土中大直径单桩分别在水平静力和循环荷载作用下的受力和变形特性。验证了通过实测桩身弯矩推算桩身变形和桩周土反力的有效性,分别获得了干砂和饱和砂的大直径单桩水平静力p–y曲线。在修正p–y曲线初始刚度的基础上,采用双曲线型p–y曲线分析了水平受荷大直径单桩的内力和变形。揭示了水平单向循环荷载下大直径单桩的桩身变形及内力变化特性,试验结果显示桩身变形和最大弯矩近似与循环次数的对数线性相关。最后,由各循环次数下的桩身弯矩获得了大直径单桩水平循环p–y曲线,提出了循环应力比相关的p–y曲线循环弱化因子,以及相应的桩基变形累积和内力变化分析方法。
Large-diameter pile foundations are more and more widely used in ocean engineering. The current p-y curve approach given in the API code cannot be used for large-diameter piles subjected to lateral loads. To deal with this problem,the behaviors of large-diameter piles in sand under lateral static and cyclic loadings are investigated based on several centrifugal model tests. The calculation approach for lateral displacement of pile shaft and soil reaction force using the measured bending moment of the pile shaft is verified. Static p-y curves of large-diameter piles in both dry and saturated sands are also obtained.By modifying the initial stiffness of p-y curves,a series of hyperbolic p-y curves are adopted to compute internal force and deformation of large-diameter piles. The change of deformation and internal force of large-diameter pile foundations under one-way cyclic loading is released. The test results show that the head displacement and the maximum moment of pile shaft almost linearly increase logarithmically with number of cycles. Finally the cyclic p-y curves of large-diameter pile foundations according to bending moment of the pile shaft in each cycle are obtained. A cyclic degradation factor related to the cyclic stress ratio and a corresponding approach for analyzing cyclic deformation and internal force of the pile shaft are proposed.
Large-diameter pile foundations are more and more widely used in ocean engineering. The current p-y curve approach given in the API code cannot be used for large-diameter piles subjected to lateral loads. To deal with this problem,the behaviors of large-diameter piles in sand under lateral static and cyclic loadings are investigated based on several centrifugal model tests. The calculation approach for lateral displacement of pile shaft and soil reaction force using the measured bending moment of the pile shaft is verified. Static p-y curves of large-diameter piles in both dry and saturated sands are also obtained.By modifying the initial stiffness of p-y curves,a series of hyperbolic p-y curves are adopted to compute internal force and deformation of large-diameter piles. The change of deformation and internal force of large-diameter pile foundations under one-way cyclic loading is released. The test results show that the head displacement and the maximum moment of pile shaft almost linearly increase logarithmically with number of cycles. Finally the cyclic p-y curves of large-diameter pile foundations according to bending moment of the pile shaft in each cycle are obtained. A cyclic degradation factor related to the cyclic stress ratio and a corresponding approach for analyzing cyclic deformation and internal force of the pile shaft are proposed.
引文
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[3]KIM B T,KIM N K,LEE W J,et al.Experimental load-transfer curves of laterally loaded piles in Nak-Dong River sand[J].Journal of Geotechnical and Geoenvironmental Engineering,2004,130(4):416–425.
[4]ASHOUR M,NORRIS G.Modeling lateral soil-pile response based on soil-pile interaction[J].Journal of Geotechnical and Geoenvironmental Engineering,ASCE,2000,126(5):420–427.
[5]REESE L C,MATLOCK H.Non-dimensional solutions for laterally loaded piles with soil modulus assumed proportional to depth[C]//Proceedings of the 8th Texas Conference on Soil Mechanics and Foundation Engineering.Austin:Bureau of Engineering Research,University of Texas,1956.
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[14]朱斌,朱瑞燕,罗军,等.海洋高桩基础水平大变位性状模型试验研究[J].岩土工程学报,2010,32(4):521–530.(ZHU Bin,ZHU Rui-yan,LUO Jun,et al.Model tests on characteristics of ocean and offshore elevated piles with large lateral deflection[J].Chinese Journal of Geotechnical Engineering,2010,32(4):521–530.(in Chinese))
[15]ZHU B,CHEN R P,GUO J F,et al.Large-scale model and theoretical investigations on lateral collisions to elevated piles[J].Journal of Geotechnical and Geoenvironmental Engineering,2012,138(4):461–471.
[16]KIM B T,KIM N K,LEE W J,et al.Experimental load-transfer curves of laterally loaded piles in Nak-Dong River sand[J].Journal of Geotechnical and Geoenvironmental Engineering,2004,130(4):416–425.
[17]TERZAGHI K.Evaluation of coefficient of subgrade reaction[J].Géotechnique,1955,5:297–326.
[18]ZHANG L,SSLVA F,GRISMALA R.Ultimate lateral resistance to piles in cohesionless soils[J].Journal of Geotechnical and Geoenvironmental Engineering,2005,131(1):78–83.
[19]FLEMING W G K,WELTMAN A J,RANDOLPH M F,et al.Piling engineering[M].Glasgow and London:Surrey University Press,1992.
[20]HETTLER A.Verschiebung Starrer und Elastischer Gründungsk rper in Sand bei Monotoner und Zyklischer Belastung[D].Ver”oentlichungen des Institutes für Bodenmechanik und Felsmechanik der Universit t Fridericiana in Karlsruhe,Deutsch-land,1981,Heft 90.(German)
[21]POULOS H G.Single pile response to cyclic lateral load[J].Journal of the Geotechnical Engineering Division,ASCE,1982,108(3):355–375.
[2]YAN L,BYRNE P M.Lateral pile response to monotonic pile head loading[J].Canadian Geotechnical Journal,1992,29:955–970.
[3]KIM B T,KIM N K,LEE W J,et al.Experimental load-transfer curves of laterally loaded piles in Nak-Dong River sand[J].Journal of Geotechnical and Geoenvironmental Engineering,2004,130(4):416–425.
[4]ASHOUR M,NORRIS G.Modeling lateral soil-pile response based on soil-pile interaction[J].Journal of Geotechnical and Geoenvironmental Engineering,ASCE,2000,126(5):420–427.
[5]REESE L C,MATLOCK H.Non-dimensional solutions for laterally loaded piles with soil modulus assumed proportional to depth[C]//Proceedings of the 8th Texas Conference on Soil Mechanics and Foundation Engineering.Austin:Bureau of Engineering Research,University of Texas,1956.
[6]BROMS B.Lateral resistance of piles in cohesionless soil[J].Journal of Soil Mechanics and Foundation Division,ASCE,1964,90(SM3):23–156.
[7]DAVISSON M T.Lateral load capacity of piles[J].Highway Research Record,1970,333:104–112.
[8]LONG J,VANNESTE G.Effects of cyclic lateral loads on piles in sand[J].Journal of Geotechnical Engineering,1994,120(1):225–244.
[9]LITTLE R L,BRIAUD J L.Full scale cyclic lateral load tests on six single piles in sand[R].Miscellaneous Paper GL-88-27,Geotechnical Div Texas A&M Univ,College Station,1988.
[10]ROSQUOET F,THOREL L,GARNIER J,et al.Lateral cyclic loading of sand-installed piles[J].Soils and Foundations,2007,47(5):821–832.
[11]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 Mechanics2011,32(7):1926–1930.(in Chinese))
[12]DYSON G,RANDOLPH M.Monotonic lateral loading of piles in calcareous sand[J].Journal of Geotechnical and Geoenvironmental Engineering,2001,127(4):346–352.
[13]徐光明,章卫民.离心模型中的粒径效应和边界效应研究[J].岩土工程学报,1996,18(3):80–85.(XU Guang-ming,ZHANG Wei-min.A study of size effect and boundary effect in centrifugal tests[J].Chinese Journal of Geotechnical Engineering,1996,18(3):80–85.(in Chinese))
[14]朱斌,朱瑞燕,罗军,等.海洋高桩基础水平大变位性状模型试验研究[J].岩土工程学报,2010,32(4):521–530.(ZHU Bin,ZHU Rui-yan,LUO Jun,et al.Model tests on characteristics of ocean and offshore elevated piles with large lateral deflection[J].Chinese Journal of Geotechnical Engineering,2010,32(4):521–530.(in Chinese))
[15]ZHU B,CHEN R P,GUO J F,et al.Large-scale model and theoretical investigations on lateral collisions to elevated piles[J].Journal of Geotechnical and Geoenvironmental Engineering,2012,138(4):461–471.
[16]KIM B T,KIM N K,LEE W J,et al.Experimental load-transfer curves of laterally loaded piles in Nak-Dong River sand[J].Journal of Geotechnical and Geoenvironmental Engineering,2004,130(4):416–425.
[17]TERZAGHI K.Evaluation of coefficient of subgrade reaction[J].Géotechnique,1955,5:297–326.
[18]ZHANG L,SSLVA F,GRISMALA R.Ultimate lateral resistance to piles in cohesionless soils[J].Journal of Geotechnical and Geoenvironmental Engineering,2005,131(1):78–83.
[19]FLEMING W G K,WELTMAN A J,RANDOLPH M F,et al.Piling engineering[M].Glasgow and London:Surrey University Press,1992.
[20]HETTLER A.Verschiebung Starrer und Elastischer Gründungsk rper in Sand bei Monotoner und Zyklischer Belastung[D].Ver”oentlichungen des Institutes für Bodenmechanik und Felsmechanik der Universit t Fridericiana in Karlsruhe,Deutsch-land,1981,Heft 90.(German)
[21]POULOS H G.Single pile response to cyclic lateral load[J].Journal of the Geotechnical Engineering Division,ASCE,1982,108(3):355–375.