Conservative rehabilitation interventions of masonry highway tunnels along the historic Genoa Po Valley Motorway in Genoa (Italy)

The present work deals with the structural safety assessment of existing tunnel masonry linings. Until the introduction of reinforced concrete masonry linings were the common solution for rail way , metro , an d road tunnels. As a result, there are still many tunnels with masonry lining that have been in service for more than a century. After such a long time , masonry linings may show signs of degradation due to ageing and the long action of water infiltration may have reduced their strength . For this reason, the safety assessment of existing tunnels is becom ing increasingly important , in order to timely identify the criticalities and plan the necessary rehabilitation interventions, but specific regulations are still lacking. This paper addresses this need by proposing a methodology for the global and local static verification of masonry tunnel linings , describing the issues to be addressed and proposing a procedure to define the mechanical properties of the masonry , calibrat e the partial safety factors , identify the local vulnerabilities and their priority order . In this process, the scientific literature and normative references developed for cultural heritage masonry structures are taken into account, considering that these t unnels have features and problems similar to old masonry constructions (bridges, porches, vaulted buildings) and that the interventions planned should also have a conservative approach, since these structures represent indeed an important element of the history of our architectural and technological evolution