砂土地基中V-H-M组合荷载下单桩分析方法研究
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摘要
海上风力发电机的大直径桩通常会受到多向荷载共同作用。在实践设计中,基础的竖向和水平承载性能是独立分开设计的,但大量研究证明竖向荷载对桩基水平承载性能具有重要的影响。将竖向荷载对大直径单桩水平承载性能的影响划分为3部分:(1)竖向荷载对桩周p–y曲线影响;(2)P–(35)效应;(3)桩侧摩阻力引起的反向弯矩。然后,以楔形体模型为基础考虑竖向荷载对桩侧土抗力极限值pu的影响推导了修正p–y曲线计算公式,在传统水平受荷桩的弹性地基梁方程中引入P–(35)效应和桩侧摩阻力引起反向弯矩,建立了均质砂土中承受水平力、竖向力及弯矩三向组合荷载下的单桩的分析方法。并将该方法应用于既有案例,验证了该理论方法的可行性。
The large-diameter monopiles of offshore wind turbines are always subjected to multiaxial loads. The design criteria for the vertical and lateral bearing behaviors of piles are designed independently, while lots of tests show that the vertical load has a remarkable influence on the lateral bearing capacity. The effect of the vertical load on the lateral behaviors of the large-diameter monopiles can be distinguished into three aspects:(1) the variation of the ultimate resistance pu of p-y curve caused by vertical loads;(2) P-(35) effect;(3) the resisting bending moment MR generated by the uneven distribution of vertical skin friction. Based on the theory of passive wedge failure model as well as the influence of the ultimate soil resistance per unit length pu caused by the vertical loads, the corrected p-y curves for sand are obtained respectively. Furthermore, an analysis method for the monopiles inserted in sand under combined loads, including the lateral load, vertical load and moment, is established, which is based on the elastic-foundation beam theory of the traditional lateral-loaded pile, taking the P-(35) effect and MR effect into considerations. Finally, it is proved that the theoretical results are feasible, applicable and reasonable by analyzing several project cases.
The large-diameter monopiles of offshore wind turbines are always subjected to multiaxial loads. The design criteria for the vertical and lateral bearing behaviors of piles are designed independently, while lots of tests show that the vertical load has a remarkable influence on the lateral bearing capacity. The effect of the vertical load on the lateral behaviors of the large-diameter monopiles can be distinguished into three aspects:(1) the variation of the ultimate resistance pu of p-y curve caused by vertical loads;(2) P-(35) effect;(3) the resisting bending moment MR generated by the uneven distribution of vertical skin friction. Based on the theory of passive wedge failure model as well as the influence of the ultimate soil resistance per unit length pu caused by the vertical loads, the corrected p-y curves for sand are obtained respectively. Furthermore, an analysis method for the monopiles inserted in sand under combined loads, including the lateral load, vertical load and moment, is established, which is based on the elastic-foundation beam theory of the traditional lateral-loaded pile, taking the P-(35) effect and MR effect into considerations. Finally, it is proved that the theoretical results are feasible, applicable and reasonable by analyzing several project cases.
引文
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[2]王卫中.砂土中组合荷载下柔性单桩承载机理研究[D].上海:同济大学,2013.(WANG Wei-zhong.Research on bearing mechanism of single pile under combined loads in sandy ground[D].Shanghai:Tongji University,2013.(in Chinese))
[3]KARTHIGEYAN S,RAMAKRISHNA V V G S T,RAJAGOPAL K.Numerical investigation of the effect of vertical load on the lateral response of piles[J].Journal of Geotechnical and Geoenvironmental Engineering,2007,133(5):512-521.
[4]张静.竖向荷载对大直径管桩水平承载特性影响的数值模拟和模型试验[D].上海:同济大学,2014.(ZHANG Jing.Numerical simulation and modeling test of the influence of vertical load on the lateral response of large-diameter pile[D].Shanghai:Tongji University,2014.(in Chinese))
[5]赵明华.轴向和橫向荷载同时作用下的桩基计算[J].湖南大学学报(自然科学版),1987,14(2):66-81.(ZHAOMing-hua.The calculation of piles under simultaneous axial and lateral loading[J].Journal of Hunan University(Natural Science),1987,14(2):66-81.(in Chinese))
[6]MCCLELLAND B,FOCHT J A.Soil modulus for laterally loaded piles[J].Journal of the Soil Mechanics and Foundations Division,1958,82:1-22.
[7]REESE L C,COX W R,KOOP F D.Analysis of laterally loaded piles in sand[C]//Proceedings of the 6th Annual Offshore Technology Conference.Houston,1974:473-485.
[8]REESE L C,WELCH R C.Lateral loading of deep foundations in stiff clay[J].Journal of the Geotechnical Engineering Division,1975,101(7):633-649.
[9]NORRIS G M.Theoretically based BEF laterally loaded pile analysis[C]//Proceedings of the 3rd International Conference on Numerical Methods in Offshore Piling.London,1986:361-386.
[10]ASHOUR M,NORRIS G M,PILLING P.Lateral loading of a pile in layered soil using the strain wedge model[J].Journal of Geotechnical and Geoenvironmental Engineering,1998,124(4):303-315.
[11]MCVAY M C,NIRAULA L.Development of p-y curves for large diameter piles/drilled shafts in limestone for fbpier[R].Gainesville:University of Florida,2004.
[12]王国粹,杨敏.砂土中水平受荷桩非线性分析[J].岩土力学,2011,32(增刊2):261-267.(WANG Guo-cui,YANGMin.Nonlinear analysis of laterally loaded piles in sand[J].Rock and Soil Mechanics,2011,32(S2):261-267.(in Chinese))
[13]XU L Y,CAI F,WANG G X,et al.Nonlinear analysis of laterally loaded single piles in sand using modified strain wedge model[J].Computers and Geotechnics,2013,51(2):60-71.
[14]REESE L C,COX W R,GRUBBS B R.Lateral load test of instrumented piles in sand at Mustang Island[R].Houston:Shell Development Company,1967.()