非均质地基中隧道开挖对被动单桩受力特性的影响

Effect of tunneling on mechanical behaviors of passive single pile in heterogeneous foundation

基于剪切位移法和Winkler模型采用两阶段分析方法探讨非均质地基中隧道开挖对被动单桩受力特性的影响。首先根据Loganathan修正的解析式估算隧道周边土体的竖向位移并将位移模式作用于桩身,然后建立被动单桩的竖向位移微分方程,采用有限差分法得出隧道开挖引起的单桩沉降与受力的解析解,最后讨论了隧道埋深和直径、桩基与隧道中线水平距离、平均地层损失比、单桩直径和刚度等参数变化对被动单桩受力特性的影响。结果表明,被动单桩的竖向位移、桩身轴力及桩周摩阻力随隧道埋深的增加均呈先增大后减小的趋势;地层损失比及隧道开挖断面尺寸对桩基竖向受力特性的影响很大,而单桩混凝土强度等级对其影响较小;桩径和桩身刚度增加到一定程度后,被动单桩的竖向受力特性趋于稳定。

Effect of tunneling on the bearing behaviors of passive single pile in heterogeneous founda-tion was studied by using two-stage method based on the shear deformation method and Winkler mod-el.Firstly,the analysis formula modified by Loganathan was used to estimate the free settlement of soil around the tunnel,then the displacement mode was applied to the pile.Secondly,differential e-quations calculating the vertical displacement of the passive single pile were built and analytical solu-tions of the single pile’s settlement and force due to tunneling were obtained by finite difference meth-od.Finally,influences of such parameters as tunnel’s depth and diameter,horizontal distance be-tween pile and tunnel,average ground loss ratio and pile’s diameter and rigidity on the bearing behav-iors of the passive single pile were discussed.The results show that,vertical settlement,axial force and skin friction of the single pile increase firstly and then decrease with the increase of tunnel depth;vertical bearing behaviors of the single pile are seriously affected by ground loss ratio as well as tunnel excavation cross-section size and less affected by the pile’s concrete strength grade.The pile’s vertical bearing begin to stabilize when its diameter and rigidity increase to a certain degree.