Novel automated repair approaches for masonry tunnels: Feasibility and sustainability

• Innovative multi-tiered framework to define innovative automated repair strategies. • Study encompassing process, costing, life cycle and simplified layered analyses. • Feasibility and sustainability study applied to patch repair of masonry tunnels. • Definition of global sustainability index for 38 novel solutions. Existing methods for patch repair in masonry tunnels are time-consuming, heavily reliant on manual labour, and inadequate to address the maintenance needs of the UK’s ageing Victorian railway tunnel network. This paper proposes a systematic framework to define innovative automated repair strategies by amalgamating various repair concepts, manufacturing techniques, and materials. Through this framework, the study examines 38 feasible alternatives, incorporating approaches such as robotic spraying, additive manufacturing, automated cutting, and the utilisation of advanced cementitious materials and composites. A thorough sustainability assessment, covering environmental, economic, social, and technical dimensions, guides the identification of the most appropriate repair solution. This assessment involves simplified process analysis, cost evaluation, life cycle analysis, and layered analysis, all integrated into a multicriteria decision-making (MCDM) methodology to derive a comprehensive sustainability index.