Abstract: Based on inspection data, the authors analyze and summarize the main types and distribution characteristics of tunnel structural defects. These defects are classified into three types: surface defects, internal defects, and defects behind the structure. To address the need for rapid detection of different defect types, the current state of rapid detection technologies and equipment, both domestically and internationally, is systematically reviewed. The research reveals that surface defect detection technologies and equipment have developed rapidly in recent years. Notably, the integration of machine vision and laser scanning technologies have significantly improved detection efficiency and accuracy, achieving crack detection precision of up to 0.1 mm. However, the noncontact rapid detection of internal and behind-the-structure defects remains constrained by hardware limitations, with traditional detection remaining dominant. Nevertheless, phased array radar, ultrasonic, and acoustic vibration detection technologies have become research hotspots in recent years, offering promising directions for detecting these challenging defect types. Additionally, the application of multisensor fusion technology in rapid detection equipment has further enhanced detection capabilities. Devices such as cameras, 3D laser scanners, infrared thermal imagers, and radar demonstrate significant advantages in rapid detection. Future research in tunnel inspection should prioritize breakthroughs in rapid detection technologies for internal and behind-the-structure defects. Efforts should also focus on developing multifunctional integrated detection vehicles that can simultaneously inspect both surface and internal structures. Furthermore, progress in fully automated, intelligent systems with precise defect identification and real-time reporting will be essential to significantly improve the efficiency and accuracy of tunnel inspection.

Key words: tunnel, structural defect, inspection techniques; inspection equipment, rapid inspection