Inspections and classification of segneSegmental lining tunnels are widely used in modern underground infrastructure, which makes them susceptible to various defects. Segmental lining tunnel defects can develop during different phases of the tunnel life cycle, from segment production in the precast plant to transportation, installation on site, and long-term operation. Many of these defects are not random but can be anticipated based on their origin and development mechanisms. A comprehensive understanding of damage types therefore allows defects to be identified based on their characteristics and causes, supporting a more reliable evaluation. One of the parts that this thesis focuses on is the role of inspection in identifying damage.