为探究桩端土强度对超长桩承载性状的影响，建立了 3 种不同长度的超长桩。通过改变桩端土的强度， 在荷载作用下，研究轴力沿着桩身传递、桩侧摩阻力的影响及桩自身变形。分析了桩端土强度的提高对超长桩上 段和下段桩侧摩阻力的影响。研究结果表明：桩端土强度提高 1～2 倍时，超长桩极限承载力提高 7.06%～22.49%； 80m 基桩对应 5 种不同长径比时，长度增加 25%～50%，其极限承载力提高 35.06%～63.21%；在同级荷载作用下， 桩端土强度高的桩侧摩阻力发挥小于桩端土强度低的；端阻强化效应在桩端土强度较弱的土层中也存，且长径比 越小增强的效应越明显；该研究可以为实际工程中超长大直径桩基设计和承载力估算提供参考。
In order to investigate the influence of soil strength at end of pile on bearing capacity of super-long piles, three kinds of super-long piles with different lengths were established. By changing the strength of soil at end of pile, the transfer of axial force along the pile body, the influence of pile lateral friction resistance and the deformation of pile were studied. The influence of soil strength on the lateral friction of the upper and lower sections of super-long piles was analyzed. The results show that, the ultimate bearing capacity of super-long pile is improved from 7.06% to 22.49%, when the soil strength of pile tip is increased by 1 to 2 times. When the 80 m foundation pile with five different length to diameter ratios, the ultimate bearing capacity increases from 35.06% to 63.21%, when the length increases from 25% to 50%. Under the same load, the lateral friction of pile with strong soil at end of pile is less than that of pile with weak soil. End-resistance strengthening effect also exists in the weak soil layer. The strengthening effect will increase with the decreasing of length to diameter ratio. The numerical simulation results can provide reference for the design and bearing capacity estimation of super-long diameter pile foundation.
WANG Si, ZHANG Yong-jie, CHENG Xin, et al. Numerical analysis of influence of soil strength of pile tip on bearing capacity of overlong pile[J]. Journal of Transport Science and Engineering,2021,37(2):68-75.