An Experimental Campaign on Real-Scale SFRC Extruded Tunnel Segments

Thanks to the use of steel fibers, concrete can enhance its toughness, achieving a better control of the post-cracking phase behaviour. Steel Fiber Reinforced Concrete (SFRC) has been largely employed by practitioners in different applications, including tunnel linings and precast tunnel segments. Working mainly under compression, tunnel linings do not require high percentages of steel reinforcement, which can be entirely replaced by the addition of steel fibers in the concrete matrix. As a matter of fact, fibers will help in the control of the cracking of tunnel structures which is more difficult to obtain for ORC structures because of the design method, which is mainly concentrated on the ultimate limit state. This paper will focus on a new methodology for the regeneration of existing tunnels based on the extrusion of SFRC new lining against the existing tunnel. In addition to small-scale tests performed to identify the material properties of the proprietary SFRC mix, an experimental campaign is currently undergoing at the Elsa Laboratory of the EC Joint Research Center in Ispra (Italy), on real-scale extruded FRC tunnel segment mock-ups in order to assess their behaviour in service under different loading combinations, and to evaluate their ultimate load bearing capacity. The paper is going to present the results of two nominally identical tests, performed so far, together with their analysis and validation according to the fib Model Code 2010 design criteria.