桩基础影响下既有地铁隧道截面内力计算研究

Subway Tunnel Section Inner Force Induced by Pile Foundation

城市已建地铁隧道的保护是目前市政建设中需要考虑的重要问题之一,针对非挤土桩和挤土桩两种桩型新建桩基础影响下既有地铁隧道的截面内力计算展开研究。采用"二阶段"法研究思想,首先基于桩基础荷载传递法、Mindlin位移解及柱孔扩张理论,分别计算得到非挤土桩和挤土桩在隧道截面位置处产生的土体位移。之后,将隧道衬砌简化为环形弹性地基梁模型,同时考虑土体抗力的影响,并将土体位移施加到环形地基梁模型,从而得到2种桩型引起的隧道衬砌截面的内力分布。研究过程中将理论结果与既有土工离心机试验进行了对比分析。研究结果表明:①计算方法得到的衬砌内力与既有文献土工离心式试验值差别不大且趋势一致,验证了计算方法的合理性;②挤土桩施工引起的隧道弯矩最大值增量远大于非挤土桩在极限荷载时的增量;③隧道截面弯矩最大值位置与桩端-隧道圆心相对位置有直接关系,大约位于桩端-隧道圆心连线相交处。

Existing tunnel protection is a key problem during urban construction. This paper focus on the inner force in tunnel sections induced by newly built pile foundation including non-displacement pile and displacement pile.‘Two-step’method was used in this paper. Firstly,based on the pile foundation theory,Mindlin solution and Column hole expansion theory,the soil displacement induced by non-displacement pile and displacement pile in the tunnel lining was obtained. Then,considering the soil reaction,tunnel section inner force induced by the two types of pile foundations was calculated by simplifying the lining as a circular elastic foundation beam. Finally,the calculated results were compared with that of the geo-centrifuge test. Results show that the theoretical solution results of lining moment are consistent with the test results. This proves the rationality of the presented calculation method. Meanwhile,the tunnel internal force caused by the displacement pile is much larger than that by the non-displacement pile under ultimate load. The maximum internal force position on the tunnel section is directly related to the relative position of the pile end and the tunnel center,and the position is near the cross line of the pile bottom and tunnel center.