The infrastructural network strengthens modern societies by enabling the efficient movement of people, goods, and services, with tunnels playing a pivotal role in regions marked by challenging topography, dense urbanization, or limited surface space. In urbanized contexts, underground space utilization has grown rapidly, improving mobility by alleviating congestion, reducing travel times and accident risks, and freeing surface land for public and environmental uses. While the demand for new tunnels continues to grow, the maintenance and refurbishment of existing ones have become equally critical. In Italy, where a large share of the tunnel stock has service lives exceeding 30 years, deterioration due to seismic exposure, traffic loads, and environmental factors calls for strategic rehabilitation approaches that go beyond conventional methods. This thesis introduces and supports the validation of the ETLR (Extruded Tunnel Lining Refurbishment) technology as an innovative and efficient solution for tunnel rehabilitation. The research encompassed the development and optimization of a tailored steel fibre reinforced concrete mix capable of meeting the specific rheological and mechanical demands of a continuous slip-forming process. The behaviour of the material was investigated from the fresh to the hardened state, through a combination of laboratory testing and numerical modelling. Structural performance was assessed via an extensive experimental campaign on small-scale specimens and full-scale tunnel mock-ups, supported by advanced numerical simulations to capture real-scale behaviour. In parallel, a comprehensive environmental and socio-economic evaluation was conducted through life-cycle assessment, comparing the ETLR process with conventional refurbishment methods in terms of sustainability and operational efficiency. Beyond validating a specific technology, this research offers a broader methodological contribution by proposing an integrated, multi-disciplinary framework that combines material science, structural mechanics, and sustainability assessment. This approach provides a robust basis not only for the implementation of the ETLR method, but also for the design and evaluation of fibre reinforced concrete tunnel linings in general, laying the foundation for a more efficient, resilient, and performance-driven future for underground infrastructure.
La rete infrastrutturale rappresenta un pilastro fondamentale delle società moderne, favorendo il movimento efficiente di persone, beni e servizi, con le gallerie che svolgono un ruolo cruciale in contesti caratterizzati da topografie complesse, elevata urbanizzazione o spazio superficiale limitato. In ambito urbano, l’impiego dello spazio sotterraneo è in costante crescita, migliorando la mobilità grazie alla riduzione della congestione stradale, dei tempi di percorrenza e del rischio di incidenti, e liberando superfici per usi pubblici e ambientali. Sebbene la richiesta di nuove gallerie sia in continuo aumento, la manutenzione e il risanamento di quelle esistenti si rivelano altrettanto fondamentali. In Italia, dove una parte significativa del parco gallerie ha superato i 30 anni di servizio, il degrado dovuto a sollecitazioni sismiche, carichi di traffico e agenti atmosferici impone strategie di riqualificazione che vadano oltre i metodi convenzionali. Questa tesi introduce ed offre la validazione della tecnologia ETLR (Extruded Tunnel Lining Refurbishment) come soluzione innovativa ed efficiente per il risanamento delle gallerie. L’attività di ricerca ha riguardato lo sviluppo e l’ottimizzazione di un mix di calcestruzzo fibrorinforzato specificamente progettato per rispondere alle esigenze reologiche e meccaniche di un processo di estrusione continua con cassero scorrevole. Il comportamento del materiale è stato studiato a partire dallo stato fresco a quello indurito, attraverso prove di laboratorio e modellazioni numeriche. La risposta strutturale è stata valutata mediante un’estesa campagna sperimentale sia su provini in scala ridotta sia su mock-up in scala reale, opportunamente affiancata da simulazioni numeriche avanzate volte a riprodurre il comportamento effettivo del rivestimento. Parallelamente, è stata condotta un’analisi a ciclo di vita per confrontare l’impatto ambientale e socio-economico della tecnologia ETLR rispetto ai metodi tradizionali di risanamento delle gallerie. Oltre alla validazione di una specifica tecnologia, il lavoro propone un contributo metodologico più ampio, fondato su un approccio integrato e multidisciplinare che unisce scienza dei materiali, meccanica strutturale e valutazione della sostenibilità. Tale approccio fornisce una base solida non solo per l’implementazione della tecnologia ETLR, ma anche per la progettazione e l’analisi di rivestimenti in calcestruzzo fibrorinforzato, ponendo le basi per un futuro più efficiente, resiliente e prestazionale delle infrastrutture sotterranee.
An advanced tunnel refurbishment methodology based on slipforming fast-setting steel fibre reinforced concrete
MARCUCCI, ANDREA
2024/2025
Abstract
The infrastructural network strengthens modern societies by enabling the efficient movement of people, goods, and services, with tunnels playing a pivotal role in regions marked by challenging topography, dense urbanization, or limited surface space. In urbanized contexts, underground space utilization has grown rapidly, improving mobility by alleviating congestion, reducing travel times and accident risks, and freeing surface land for public and environmental uses. While the demand for new tunnels continues to grow, the maintenance and refurbishment of existing ones have become equally critical. In Italy, where a large share of the tunnel stock has service lives exceeding 30 years, deterioration due to seismic exposure, traffic loads, and environmental factors calls for strategic rehabilitation approaches that go beyond conventional methods. This thesis introduces and supports the validation of the ETLR (Extruded Tunnel Lining Refurbishment) technology as an innovative and efficient solution for tunnel rehabilitation. The research encompassed the development and optimization of a tailored steel fibre reinforced concrete mix capable of meeting the specific rheological and mechanical demands of a continuous slip-forming process. The behaviour of the material was investigated from the fresh to the hardened state, through a combination of laboratory testing and numerical modelling. Structural performance was assessed via an extensive experimental campaign on small-scale specimens and full-scale tunnel mock-ups, supported by advanced numerical simulations to capture real-scale behaviour. In parallel, a comprehensive environmental and socio-economic evaluation was conducted through life-cycle assessment, comparing the ETLR process with conventional refurbishment methods in terms of sustainability and operational efficiency. Beyond validating a specific technology, this research offers a broader methodological contribution by proposing an integrated, multi-disciplinary framework that combines material science, structural mechanics, and sustainability assessment. This approach provides a robust basis not only for the implementation of the ETLR method, but also for the design and evaluation of fibre reinforced concrete tunnel linings in general, laying the foundation for a more efficient, resilient, and performance-driven future for underground infrastructure.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/241597