考虑剪切变形下隧道开挖引起邻近桩基水平向响应简化分析

Simplified analysis for evaluating lateral response of adjacent pile due to tunneling considering shearing effect

隧道开挖引起邻近桩基的变形影响理论研究都将桩基简化成Euler-Bernoulli梁搁置在传统的Winkler地基模型和Pasternak地基模型上,忽视了桩基变形时桩基自身剪切变形的影响。基于两阶段分析法,采用Loganathan公式计算隧道开挖引起邻近土体自由位移场,再将桩基简化成可考虑剪切变形的Timoshenko梁放置在Kerr地基模型上,建立桩基水平方向受力平衡方程,结合桩基两端约束条件,获得邻近桩基的水平位移及其内力半解析解。随后考虑群桩间土体遮拦效应,进一步获得隧道开挖对邻近群桩的变形影响。通过与工程实测数据及有限元模型计算结果对比,验证了本文方法的合理性。研究结果表明:邻近群桩水平位移及其弯矩随着地层损失率增大而线性增大;隧道埋深增大会引起邻近群桩水平位移减小,桩基弯矩峰值在隧道埋深较大时明显减小;桩隧间距增大会引起邻近群桩水平位移及其内力减小,其减小速率逐渐变缓。

The studies about pile foundation displacement response caused by adjacent tunneling generally simplify the pile as Euler-Bernoulli beam upon traditional Winkler foundation model or Pasternak foundation model, while the shearing effect of the pile is neglected. Based on the two-stage method, the Loganathan formula is applied to calculate the neighboring soil-free displacement, and then the pile is simplified as Timoshenko beam,which can take the beam shearing effect into consideration, lying on the Kerr foundation model. The governing equation of the horizontal force balance of adjacent pile was established. Taking the boundary of the pile into consideration, the semi-analytical solution about the horizontal displacement and the internal force of the adjacent pile were delivered. Taking the soil blocking effect between pile groups into consideration, the displacement response of adjacent piles induced by tunneling was solved. By comparing with the existing actual measurement and finite element solutions, the rationality of the proposed method was verified. The results show that the horizontal displacement and bending moment of adjacent pile groups will linearly increase with the increase of ground loss ratio. The horizontal displacement of adjacent pile groups decreases with the increase of the depth of the tunnel axis, and the peak bending moment of the pile is significantly reduced when the tunnel buried depth is deeper. The increase of the tunnel-pile horizontal distance will cause the decrease of the horizontal displacement of the adjacent pile groups, but the rate of decrease slows gradually.