基于分布式光纤监测的盾构隧道管片变形受力反演分析

INVERSION ANALYSIS OF DEFORMATION AND FORCE OF SHIELD TUNNEL SEGMENTS BASED ON DISTRIBUTED OPTICAL-FIBRE MONITORING

为研究盾构隧道变形受力分布情况,依托于某盾构隧道进行了分布式光纤监测。在盾构隧道管片预制期间,将分布式光纤沿环向布设于管片内部钢筋笼的上、下表面。分别在管片安装后及变形稳定后进行了分布式光纤监测,得到管片内部真实应变分布。基于所得连续的应变数据,利用已经提出的反演分析方法计算出了监测期间管片的位移、内力及外荷载分布。反演计算结果表明,隧道监测期间盾构隧道的变形模式为向左的斜椭圆与整体环向压缩的耦合变形。由内力分布可知,在管片接头处内力的波动明显,这是由于管片接头处刚度变化导致的。为反映这种波动,管片设计中更宜采用梁-弹簧模型。给出了管片结构的破坏包络图,将反演分析所得内力值标注其中,并选取危险截面进行了结构安全校核,计算结果证明隧道管片受力安全。

In order to study the deformation and force distribution of shield tunnels,distributed optical-fibre monitoring was carried out in a shield tunnel.During the prefabrication of the shield tunnel segments,the optical fibres were arranged on the upper and lower surfaces of the reinforcement cage inside the segments,along the circumferential direction.The distributed optical-fibre monitoring was conducted after the segments were installed and after the segment deformation was stable,and the strain distribution inside the segments was obtained.The displacement,force and load distribution of the segments during the monitoring were calculated based on the continuous strain data,using the proposed inversion analysis method.The inversion calculation results showed that the deformation mode of the shield tunnel during the monitoring was the coupling deformation of the leftward oblique ovalisation and the overall circumferential compression.It can be seen from the force distribution that the fluctuation of the forces at the segment joints was obvious,which was caused by the change of stiffness at the segment joints.To reflect this fluctuation,the beam-spring model is more suitable for the segment design.The failure envelope diagram of the segments was developed,and the force values obtained by the inversion analysis were marked in it.The dangerous cross sections were selected to check the structural safety.The calculation results proved that the tunnel segments were safe.