根键布置方式对根式基础竖向承载性能的影响

文章通过现场试验和数值分析探讨根键布置方式对根式基础承载性能的影响;建立池州长江公路大桥根式基础的数值计算模型,与现场堆载试验得到的荷载-位移曲线进行对比,验证数值模型的正确性;通过分析桩顶荷载-位移曲线、桩身轴力和桩侧摩阻力,探讨根键水平布置方式、根键布置位置和相邻根键层间距对根式基础竖向承载性能的影响。结果表明:相比于传统桩基础,根键梅花形布置和等角度布置时,桩的承载力分别提高65.28%、46.71%,根键能够增大桩侧摩阻力和减小桩端阻力;根键梅花形布置能够减弱应力重叠,充分发挥根键承载潜力;根键布置在下部时,相对于布置在上部和中部,桩的承载力分别提高34.51%、14.69%,同时根键布置在下部能够减小桩端阻力;根键层间距较小时,根键端部形成环形剪切面,此时根键无法发挥作用,随着层间距增大,根键间相互影响逐渐减弱,根键趋近于独立承载。

This paper discusses the influence of roots arrangement on the vertical bearing capacity of root piles through field tests and numerical analysis. The numerical model of root piles for Chizhou Yangtze River Highway Bridge was established. Such a model was then verified by the load-displacement curves obtained from the field stacked load test. The effects of roots horizontal layout, roots position, and root layers spacing on the vertical bearing capacity of root piles were discussed with the verified numerical model by analyzing the load-displacement curves, axial force and shaft friction. The results show that the bearing capacities of roots staggered arrangement and non-staggered arrangement are improved by 65.28% and 46.71% compared with that of the traditional pile. Moreover, the roots can increase the shaft friction and reduce the end resistance of root piles. The bearing capacity of roots can be fully mobilized because roots staggered arrangement can reduce the overlap of stress. The bearing capacity of roots arranged at the lower section is improved by 34.51% and 14.69% compared with those of roots arranged at the upper and middle sections. Meanwhile, the end resistance can be reduced obviously when roots are arranged at the lower section. As the root layers spacing is small, the bearing capacity of roots cannot be mobilized because a cylindrical shear failure surface is formed at the end of roots. The interaction among roots decreases with the increase of root layers spacing, the roots tend to share the load independently.