A Simple Parametric Numerical Model to Assist the Design of Repair Works and Maintenance of Tunnels

Tunnels are resilient infrastructures whose service life is generally much higher than the designed nominal one, thus increasing the number of existing tunnels still in operation with an average service life of more than 50 years. From a more Italian perspective, Italy’s complex morphology has made it necessary to excavate a considerable number of tunnels to develop the nowadays railway and motorway traffic lines. However, recent cases of tunnel lining local collapses have highlighted that some existing Italian tunnels have almost reached the end of their service life, revealing their maintenance, refurbishment and/or upgrading works to be an urgent need. Taking advantage of the tunnel refurbishment plan ongoing in Italy, the aim of this study is to support the design of temporary maintenance works by means of simple numerical modelling. In such a way it is possible to consider fundamental geotechnical parameters that can play a key role in the effectiveness and in the applicability of the studied maintenance solutions. The attention is here devoted to interventions with suspended steel ribs to prevent local instabilities of the aged concrete.