Post-cracking performance criteria for Fibre-Reinforced Sprayed Concrete in permanent tunnel linings

Fibre reinforced sprayed concrete linings offer potential safety, cost, and environmental benefits compared to traditional solutions. However, current standards and recommendations may not sufficiently persuade the tunnel construction industry to adopt this material for permanent tunnel lining applications. There is a pressing need for further exploration into the post-cracking performance to improve the design process of sprayed FRC permanent tunnel linings. In addressing this need, two critical aspects come into focus: the characterization of FRC material and the subsequent determination of uniaxial tensile law. Concerning the first aspect, EFNARC proposed the use of three-point bending test on square panel with notch, which is now integrated into the new EN14488-3. In this regard, experimental tests were carried out on concrete panels reinforced by macro synthetic fibres. Two fibre types and contents were considered. Regarding FRC uniaxial tensile law for use in the lining design process, the procedure to be adopted is still an open matter. It is herein proposed to apply the inverse analysis method, typically used in case of standard beam notched samples, to the results retrieved by square panels’ tests. The main goal is to achieve the most accurate description of FRC post-cracking performance for use in the numerical simulations of embedded in ground condition of permanent sprayed concrete linings.