Tunnel conditions assessment based on image analysis: a new inspection procedure for railway tunnels

The total length of Swiss railways tunnels today covers more than 250 km of the entire network and will be increased by more than 65% in the next 10 years. It is then clear that tunnel condition survey and assessment are key topics for ensuring safe operation. In spite of these conclusions, the time allowed for inspections and maintenance has been continuously reduced due to the growing train frequency. Therefore, in recent years it has been necessary to revise completely the inspection procedure as well as the tools employed for performing the inspection and assessing tunnel conditions. Thanks to the introduction of new techniques mainly based on laser scanning image analysis it has been possible to considerably reduce the inspection time spent at night in the tunnel. Moreover, the use of laser scan to assess tunnel condition not only improves the duration of the inspection itself but also gives better quality and consistency in terms of inspection results. The complete reorganisation of the inspection procedure resulted in the publication of a new internal guideline. This paper will present how tunnel inspections are conducted today at SBB and give some examples of application and results.