PHC-钢管组合桩竖向荷载传递机理研究

Investigation of vertical load transfer mechanism for PHC-steel composite pile

PHC-钢管组合桩因抗腐蚀、贯入性能好,在高桩码头开始推广使用。但是其上部是PHC管桩,下部是钢管桩,两者桩径不同,弹性模量和密度等差异很大,荷载在桩体中的传递呈现出不同的作用机理,传统计算方法无法直接应用于其竖向承载力计算,而且该桩型竖向荷载传递机理研究未见报道,导致PHC-钢管组合桩竖向荷载设计缺少机理依据。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。

PHC-steel composite pile,with corrosion resistance and good penetration properties,has been popularized in high-pile 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 PHC-steel composite pile was conducted by using FLAC3 Dsoftware,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 PHC-steel composite pile which driven in Yangtze River region of Zhenjiang Yangzhong is end-bearing 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.