Review of Railway Operation Tunnel Inspection System and Condition Assessment Method

Currently, the expanding scale of railway tunnels in operation raises higher requirements for effective management thereof so as to ensure their safe operation. Just in this context, this paper compares and analyzes the tunnel inspection systems, condition assessment methods and technical equipment prevailing in many countries including Japan, European countries, the United States and China. Study results show that in terms of tunnel inspection systems, various countries have set their respective tunnel inspection cycles according to the tunnel integrity, service duration, service status, speed level and other factors. In particular, Japan and Europe have designed the tunnel inspection procedures, putting forward requirements for the professional competence of inspectors. In terms of condition assessment, Japanese standards are more hierarchical and systematic in the integrated application related to lining crack, deformation and defect, but are insufficient in the assessment of serious internal lining defects. In contrast, European standards focus on the impact of diseases on the overall performance of the tunnel structure. In addition, Chinese standards highlight the single-indicator assessment, but ignore the correction of assessment results in case of multiple deterioration types. It's worth noting that Japan and China have respectively developed their own rail-mounted tunnel inspection devices to replace manual inspection. Based on a comprehensive comparison of tunnel inspection systems and condition assessment methods of different countries, according to the scale, inspection device technical level and service characteristics of China's railway tunnels, this paper proposes a framework of railway tunnel inspection regulation, while optimizing and supplementing the contents and requirements of relevant tunnel inspection regulation.