基于分布式光纤应变传感技术的盾构隧道横截面收敛变形监测方法

Convergence deformation monitoring of shield tunnels based on distributed optical fiber strain sensing technique

横截面收敛变形是评估盾构隧道运营期间结构稳定性和安全性的重要指标,但现有的监测手段仅能满足对有限个等间距预设断面收敛变形的监测需求,对长达几公里以上的隧道任意断面进行全面的收敛变形监测还存在技术和经济上的困难而无法实现。采用分布式光纤应变传感器覆盖隧道全线各断面,并提出一种通过测量内壁环向应变分布监测隧道任意横截面收敛变形的方法。该方法得到的收敛变形与应变分布呈显式线性关系,变形监测精度主要由传感器应变测量精度决定。其次,通过有限元算例的计算结果证明了所提方法的正确性。最后,通过横向盾构隧道缩尺模型试验测试了所提方法对收敛变形的实测精度。试验结果表明,该方法对监测收敛变形的最大误差仅为15%。

Convergence deformation is an important index for evaluating structural stability and safety during the running periods of shield tunnels. Because of some technical and economic difficulties, the traditional observation methods, which can be only used to monitor a few predetermined and uniformly spaced segment rings, can＇ t monitor convergence deformation of all segment tings of actual shield tunnels which usually have the length of several kilometers or even longer. In this study, the distributed optical fiber strain sensing technique is proposed to cover every segment rings in tunnels, and a new method is presented to monitor the convergence deformation of arbitrary rings by means of the hoop strain measurements along the rings. In the proposed method, a linear and explicit function relationship between the convergence deformation and the strain distribution is put forward, and it is found that the precision of the monitored deformation mainly depends on that of the strain measurements from the arranged distributed fiber optical sensors. Furthermore, a numerical simulation is conducted to validate the proposed method. Additionally, an experiment on a small-scale concrete segment ring model is carried out to verify the practical precision of the proposed method. Experimental results show that the maximum monitoring error of the estimated convergence deformation is only 15%.