Structural health monitoring (SHM) on railway tunnels is increasingly demanding inspection methodologies based on full‐field image‐based techniques. The relevance of adequate inspection methodologies to signal potential problems that need increased attention is at the forefront of any monitoring system for problems that can disturb tunnel's integrity. Detecting defects is decisive for an efficient inspection, investigating tunnel status, and rescheduling maintenance operations, when and where required. This paper introduces a methodology design, based on acquisition of tunnel's 3D geometry and monitoring it through time to signal the possible emergence of structural defects and return the exact position where monitoring equipment will have to be deployed to. A demonstrator is built, and the applicability and accuracy of the system is assessed through implementation of a model prototype, carried out on a scaled tunnel model. At a secondary stage inspection, imposed geometrical changes and defects of the tunnel are monitored and characterised by an optical nondestructive inspection technique based on the digital image correlation (DIC). It enables the appraisal of structural integrity on the tunnel lining through displacement and strain fields acquisition. The chief advantage of the deployed inspection system, amongst others, lies on its robust functionality in both geometrical and structural integrity inspection aspects, contributing to the establishment of a robust SHM methodology for railway tunnels over time. In conclusion, experimental results are presented for evaluating scaled tunnel condition and monitoring the tunnel profile, and further DIC data are presented inferring displacement field progress of an introduced structural defect.

中文翻译：

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用于预测性维护的铁路隧道结构监测方法建议

铁路隧道的结构健康监测（SHM）对基于全场图像技术的检查方法的要求越来越高。对于可能干扰隧道完整性的问题，任何监视系统的最前沿都是采用适当的检查方法来发出需要进一步关注的潜在问题的信号。检测缺陷对于在需要的时间和地点进行有效的检查，调查隧道状态以及重新安排维护操作至关重要。本文介绍了一种方法设计，该方法基于对隧道3D几何形状的采集并通过时间对其进行监视，以发出可能出现结构缺陷的信号，并返回必须将监视设备部署到的确切位置。建造了一个示威者，系统的适用性和准确性是通过在规模化的隧道模型上进行模型原型的实现来评估的。在第二阶段检查中，通过基于数字图像相关性（DIC）的光学非破坏性检查技术，对隧道的几何形状变化和缺陷进行监视和表征。通过位移和应变场的采集，可以评估隧道衬砌的结构完整性。除其他外，已部署的检查系统的主要优势在于其在几何和结构完整性检查方面的强大功能，从而为建立长期可靠的铁路隧道SHM方法做出了贡献。结论，