路堤荷载下刚性桩复合地基桩帽效应分析

Study on Pile Cap Effect of Rigid Pile Composite Foundation under Embankment

在分析路堤荷载作用下刚性桩复合地基中桩帽效应的基础上,通过理论分析、有限元计算、室内模型试验以及现场测试等方法,研究了桩帽以及桩帽尺寸的大小,对刚性桩复合地基中桩土分担比、加筋垫层的应力以及整体沉降特性等的影响.研究表明:桩帽的存在增加了桩顶与垫层之间的接触面积,起到均化桩顶集中力、减小桩顶向垫层刺入量的作用,使带帽刚性桩复合地基控制沉降的能力远好于不带帽刚性桩复合地基;桩帽尺寸逐渐增大,桩间土的应力明显减小,Q-S曲线由"陡降型"向"缓变形"转变,有助于带帽刚性桩复合地基整体承载力的发挥,从而提高了刚性桩复合地基的利用效率.

Based on analysis of the pile cap effects,theoretical analysis, finite element method,model tests and in-situ test are presented in this paper. The impacts of pile cap and its size on pile-soil load sharing ra- tio, stress of reinforced cushion and the overall settlement characteristics are studied. The research results show that the presence of pile cap increases contact area between pile top and cushion, which homogenizes concentrated force on pile top and reduces penetration amount of pile top into cushion. So,rigid pile com- pesite foundation with pile cap has greater ability of controlling sedimentation than that without pile cap. With pile cap size increasing, the stress of soil among piles decreases significantly and Q - S curve changes from steep drop type to slow deformation type, which does good to exert total bearing capacity and thereby enhances the utilization efficiency of rigid pile composite foundation. The size of pile cap should not be too large or too small with the view of application effect, making full use of material and economy.