Structural safety of existing masonry-tunnel-linings: A methodology derived from existing buildings approaches

Masonry linings were the primary solution for tunnels before the introduction of reinforced concrete. As a result, many tunnels with masonry linings have been in operation for over a century and may exhibit damage due to ageing and prolonged water infiltration. Currently, there are no specific regulations for the static verification of masonry tunnels. These tunnels share characteristics and problems with historic masonry structures such as bridges and building facades. Therefore, the scientific literature and normative references developed for masonry heritage structures were here considered. This work focuses on estimating the masonry strength of tunnel linings. To demonstrate the proposed methodology and the addressed problems, the 'Giovi' tunnel on the historic Genoa-Valle del Po motorway in Genoa, Italy was selected as an exemplary case. The masonry's resistance is measured in situ using flat-jacks and estimated using methodologies proposed for both new and existing buildings. The comparison of these methodologies highlights the unique characteristics of tunnel linings, including thick mortar bed-joints and massive curved masonry walls, with only one free face.