深厚软土超长预应力高强混凝土管桩轴向受力性状的试验研究

通过在管桩的钢筋笼里面添加带应变计的附加钢筋,对珠海保税区深厚软土地基中超长预应力高强混凝土(PHC)管桩进行了轴向静载试验和桩身轴力的测试,探讨了深厚软土地基中超长PHC管桩的竖向承载特性和荷载传递机理。结果表明在深厚软土地基中,超长PHC管桩表现出端承摩擦桩的承载性状,因此应当选择压缩性较小的土层作为持力层;超长PHC管桩的桩端土刚度对桩侧摩阻力的发挥有极大的影响,提高桩端土刚度对桩侧摩阻力有明显的增强作用;适当地增加桩长可以提高桩基的极限承载力;在长细比较大的超长PHC管桩设计中,除了从极限承载力和桩顶沉降来考虑外,还应该注意桩身强度的影响;同时,在沉降计算中,要充分考虑桩身压缩引起的沉降。该试验方法和试验结果对今后PHC管桩的研究和设计应用具有重要的指导意义。

Experimental study on the axial compressive behavior of super-long PHC pipe piles in deep soft soils

Based on the data analysis of loading tests on PHC(prestressed high strength concrete)pipe piles,conducted through adding two additional reinforcement steel bars with strain gauges in the reinforcement cage of the pile in the deep soft soil foundation of the Zhuhai free trade zone,the bearing capacity and load transferring mechanism of the piles are discussed.Results show that the super-long PHC pipe piles behave as end-bearing frictional piles,so the piles should be driven to a soil layer with little compressibility.The stiffness of the soil at the pile tip affects the skin friction,therefore,improving the stiffness of the soil at the pile tip may significantly improve skin friction.The bearing capacity of the super-long PHC pipe piles increases with increase of the length of the pile.It is important to consider the strength and the settlement of the pile in design,and the settlement owing to the compression of pile should be considered in the calculation of the settlement.