设计缺少机理依据。运用FLAC3D软件并基于镇江扬中长江沿岸地区地质条件，对PHC钢管组合桩进行竖向静载数值计算，同时考虑土体软化特性、桩土接触特性及沉降大变形问题，对“接桩部位埋深”、“接桩部位面积”问题进行研究。分析其不同组合下对桩身极限承载力的影响以及桩身轴力、侧摩阻力分布规律。结果表明，镇江扬中长江沿岸地区打入的PHC钢管组合桩是端承摩擦桩；接桩部位埋深与面积会影响极限承载力和桩体失稳后沉降值大小；桩身轴力在接桩部位发生较大衰减；桩侧摩阻力随深度变化较复杂；整桩侧摩阻力极值出现在接桩部位。
关键词：PHC钢管组合桩；FLAC3D软件；静载试验；接桩部位埋深；接桩部位面积；轴力；桩侧摩阻力
中图分类号：TU473.1 文献标志码：A 文章编号：16721683（2016）01013607
Investigation of vertical load transfer mechanism for PHCsteel composite pile
HU Junwen1，ZOU Yuguang2，TANG Lei1，WANG Haijun1，GUAN Fuhai1
（1.Nanjing Hydraulic Research Institute，Nanjing 210024，China；
2.Harbor Construction Project of Zhenjiang，Zhenjiang 212004，China）
Abstract：PHCsteel composite pile，with corrosion resistance and good penetration properties，has been popularized in highpile wharf.However，there are always some difference of their diameter，modulus of elasticity and density between PHC pipe pile in the upper part and steel pipe pile in the lower part，and the load transfer of composite pile was significantly different in its upper and lower part.The traditional method can not be applied directly to calculate the vertical bearing capacity，thus the load transfer mechanisms were not investigated.Therefore，the design of composite pile lacked mechanism basis.Based on geological conditions of the Yangtze River region of Zhenjiang Yangzhong，and considering softening of soil，the contact characteristics of pilesoil and great settlement deformation，simulation test of vertical static loading of PHCsteel composite pile was conducted by using FLAC3D software，then the effect of “depth of joint”，“area of joint” on ultimate bearing capacity and the axial force and pile lateral friction resistance were analyzed.The results indicated that the PHCsteel composite pile which driven in Yangtze River region of Zhenjiang Yangzhong is endbearing friction pile；the area and depth of joint affects the ultimate bearing capacity and settlement value of unstable pile；the greater attenuation of axial force occurs in the joint；the pile lateral friction resistance changes intricately with increasing depth；the ultimate pile lateral friction resistance occurs in the joint.
Key words：PHC steel composite pile；FLAC3D；vertical static loading test；depth of joint；area of joint；axial force；pile lateral friction resistance
PHC钢管组合桩是由上部预应力高强度混凝土管桩（简称PHC管桩）与下部开口钢管桩组合拼接而成，其构成见图1，该桩型具有抗腐蚀、优良的贯入性能以及较低的后期维护费用等优点。