PSI - Issue 84

Enrico Mittiga et al. / Procedia Structural Integrity 84 (2026) 867–873

873

• Calibrate the injection speeds and maximum filling heights. • Identify critical points in the connection systems.

During testing, several critical issues were identified, mainly related to the suboptimal management of the concrete filling placement. Excessive pouring speeds and uneven distribution of the material generated higher than expected pressures, causing the elements to shift and, in one case, concrete to leak onto the carriageway. These events provided valuable information that allowed us to refine the construction details and define a more rigorous and safer pouring procedure. In any case, the experimentally observed displacements of the elements from their original position were between ±5 mm in the longitudinal direction and ±6 mm in the radial direction, values that fully comply with the design assumptions. 4. Conclusions Given the large number of tunnels that characterise the Anas road network and the specific characteristics of the Italian territory, the need for adequate tunnel maintenance is a technological challenge that requires design flexibility and attention to the surrounding environment. Full-scale experiments have shown that the above-described solution significantly limits interference with road operations, improves the quality of execution and, above all, reduces construction times. The use of prefabricated self supporting linings combined with self-compacting concrete is therefore an effective and technologically advanced solution for the rehabilitation of existing road tunnels that cannot be closed to traffic on a continuous basis. The success of the intervention is strongly linked to the correct design of the transitional phases and the experimental validation of the construction procedures. Further developments could include applying the methodology to more complex geometries, integrating structural monitoring systems, and further optimising concrete mixes based on casting pressures and environmental conditions, thus enabling the technique to be extended to many more cases and situations across the network.

Acknowledgements The authors would like to thank Cancellotti Srl for their commitment during the large-scale testing phase.

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