Modern approaches to monitoring deformations of transport tunnels: technologies, principles and development trends

The article examines the evolution of transport tunnel monitoring – from episodic geodetic observations to modern digital systems. The relevance of the study is due to the aging of a significant part of the tunnel stock, the increasing complexity of geotechnical conditions, and the growing safety requirements for infrastructure. Based on an analysis of the advanced European school, key monitoring principles have been identified, including continuity, multi‑channel data acquisition, integration with computational models, and operational feedback. Stationary structural health monitoring (SHM) systems, mobile systems based on terrestrial and mobile laser scanning, as well as distributed fiber-optic sensing systems are examined. A comparative analysis of monitoring methods is conducted in terms of accuracy, spatial coverage, and operating mode. Key trends in the industry are shown: the move toward real‑time measurements, integration with digital twins, and the implementation of machine learning. The limitations of existing solutions are presented: the predominance of “fixation” monitoring and the formalization of tasks related to the early detection of deformation processes. The necessity of transitioning from monitoring as a “state survey” to predictive safety and lifecycle‑oriented management of tunnels, including in the context of the digital transformation of the industry, is substantiated.