Structural deformation monitoring during tunnel construction: a review

During the process of tunnel construction, it is crucial to regularly observe and measure the deformation of excavation surface and supporting structures to ensure the safety of constructors and the long-term stability of the tunnel structure. Monitoring the condition of tunnel structure usually involves measuring the deformation of specific points in the tunnel or measuring the convergence. However, traditional method of utilizing total station presents several issues such as the need for the installation of reflective prisms, susceptibility to human error, and inadequate monitoring frequency. Rapid advances in machine vision and sensor technology have brought new solutions for tunnel monitoring and measurement. These solutions include robotic total stations, ground-based real aperture radar, terrestrial laser scanning, vision-assisted laser, wireless sensor network with MEMS, and fiber optic sensing. Each technique offers unique advantages and capabilities for tunnel monitoring. This manuscript aims to provide a collective review of recent engineering cases and compare the advantages of these techniques. The ultimate goal is to facilitate the selection of measurement equipment that is most suitable for future projects. Graphical abstract