Sprayed tunnel linings: a comparison between several reinforcement solutions

In tunnel construction the use of sprayed concrete coupled with steel mesh or added with steel fibres for temporary and permanent linings is a well known and used solution. The paper investigates the use of A/R glass fabric reinforcement for temporary linings in order to estimate its competitiveness in terms of mechanical performance, costs and placing time. The mechanical performance of three different solutions (steel mesh, steel fibre and glass fabric) were compared by means of bending tests on slabs (600 x 600 x 100 mm). After a careful mechanical characterization of the material, the average maximum loads reached in the experimental investigation on slabs are compared with the values predicted by a limit analysis kinematic approach. A proper geometrical description of the specimens was also performed by means of laser-scanner technique in order to justify the scattering induced by the non-uniform thickness of the tested slabs due to a material hardening too fast induced by silicate addition.