盾构上跨复合岩土层既有隧道管片力学分析

Analysis of segment mechanics characteristics of shield tunnel over-spanning existing tunnel in composite rock-soil layer

目前,地铁隧道采用盾构法施工趋于常态化,但传统荷载体系在复合岩土层中盾构隧道上跨既有隧道管片的受力计算中还存在一定局限性。为解决该问题,本研究通过修正惯用法与梁-弹簧模型的优缺点,提出了关于盾构上跨复合岩土层既有隧道管片的荷载体系与计算方法,并依托长沙地铁4号线圭塘站区间隧道工程,采用有限元模型对比分析了梁-弹簧模型与本方法结果。研究结果表明:穿越盾构后,既有隧道竖向位移趋势明显,盾构隧道管片位移引起拱顶与拱底的地层被动抗力不可忽略。梁-弹簧模型夸大了盾构隧道拱底处的主动土压力,未考虑到下部岩层对盾构隧道管片切向变形抑制较弱,且其对切向弹簧的设置不合理。本方法更符合复合岩土层中盾构隧道上跨既有隧道管片的受力情况,该结论可为类似工程提供参考。

At present,the shield construction of metro tunnels tends to be normal.However,there are some limitations in using traditional load system to calculate the force of shield tunnel in composite rock-soil layer.This study proposes the load system and calculation method of the existing tunnel segment of the shield up-span composite rock-soil layer by analyzing the advantages and disadvantages of the modified conventional method and the beam-spring model.Based on the section tunnel project of Guitang Station of Changsha Metro Line 4,the results of the beam-spring model and the proposed method are compared and analyzed by establishing the finite element model.The results show that after crossing the shield,the vertical displacement trend of the existing tunnel is obvious,and the passive resistance of the stratum at the top and bottom of the arch caused by the segment displacement of the shield tunnel cannot be ignored.The beam-spring model exaggerates the active earth pressure at the arch bottom of the shield tunnel,and does not consider that the lower rock stratum has weak inhibition on the tangential deformation of the shield tunnel segment,and its setting of the tangential spring is unreasonable.The proposed method is more in line with the stress condition of the segment of the shield tunnel in the composite rock and soil layer,which can provide a reference for similar projects.