PHC-钢管组合桩竖向荷载传递机理研究

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。

Investigation of vertical load transfer mechanism for PHC2steel composite pile

PH C2steel composite pile, w ith cor rosion resistance and g oo d penet ratio n pr operties, has been po pularized in high2pile whar f. H ow ever, there are alway s some difference of t heir diameter, modulus of elast icity and density between PH C pipe pile in the upper part and steel pipe pile in the lower part , and the load tr ansfer o f com posite pile w as sig nificantly differ ent in its upper and low er part. The tr adit ional method can not be applied directly to calculate the vert ical bear ing ca pacity , thus the load tr ansfer mechanisms wer e no t investig ated. Therefor e, the desig n of compo site pile lacked mechanism basis. Based o n g eo lo gical condi2 t ions of the Yang tze River reg ion of Zhenjiang Yangzhong, and considering softening o f soil, the contact cha racteristics of pile2 soil and gr eat settlement deformation, simulation test of ver tical static loading of PH C2steel composite pile w as conducted by u2 sing FLAC3D softw are, then the effect of / depth o f jo int0, / area o f jo int0 on ult imate bearing capacit y and the ax ial force and pile later al f rictio n resistance w ere analy zed. The r esults indicated that the PH C2steel composit e pile which driven in Yang tze Riv er r egion of Zhenjiang Yangzhong is end2bear ing fr iction pile; t he area and depth o f joint affects the ult imate bearing capacity and settlement value o f unstable pile; the g reater attenuation of ax ial force occurs in the jo int ; the pile lateral friction resistance changes intr icately w ith incr easing depth; the ult imate pile lateral frict ion resistance o ccur s in the joint.