Concrete crack reduction in tunnel linings by steel fibre-reinforced concretes

• We investigate the effectiveness of SFRC for increasing the performances of a tunnel lining.
• We obtain stress–strain and stress–crack opening relations from experimental data.
• We develop a fibre model of the lining cross-section.
• The advantages of introducing steel fibres in the concrete are evident.
• The lining thickness can be reduced by introducing steel fibres.

The present paper investigates the advantages of using Steel Fibre Reinforced Concrete (SFRC) for the realisation of the lining of cast-in-place tunnels. In particular, the benefits of steel fibres in terms of serviceability limit states are investigated. Both cases of SFRC tunnel linings with and without conventional steel bars are considered. It is shown that the crack-bridging effect of the fibres significantly reduces the crack width opening in the tunnel lining for a given stress field. An optimisation criterion for the design of the lining thickness is also proposed here. The procedure is applied to a case study, the “Galleria Naturale Muro” of the Italian Highway A3 (Salerno–Reggio Calabria). With reference to concretes with different dosages of steel fibres the optimal lining thickness for a given value of crack width opening is determined.