The article discusses how the French railway network is facing the challenge of maintaining and strengthening its aging tunnels. With over half of the tunnels being over 100 years old, the focus is on methods of non-destructive testing and strengthening to ensure their safety and longevity. The researchers review the evolution of tunnels over time, the organization of tunnel surveillance, different non-destructive control methods, conditions for taking action, methodology for strengthening studies, and current repair techniques.