Multiscale Behavior of Fibre-Reinforced Concrete for Tunnel Lining Applications: Properties, Performance, and Design Considerations –A Review

This review systematically evaluates the multiscale behavior, mechanical performance, and durability of various fibre-reinforced concrete (FRC) systems tailored for tunnel lining applications.Traditional tunnel linings often suffer from limited post-cracking ductility and inadequate crack control under complex loading, leading to durability concerns and increased maintenance costs.By critically examining different fibre types -including steel, polypropylene, glass, basalt, and natural fibres -and their hybrid combinations, this study addresses these drawbacks through insights into fibre -matrix interactions and crack-bridging mechanisms at multiple scales.Advanced numerical simulation methods, such as multiscale finite element modeling and homogenization techniques, are also reviewed to facilitate optimized FRC design.The techno-economic aspects, including material cost-benefit analysis and lifecycle performance, are considered to support practical implementation.This comprehensive synthesis not only consolidates current knowledge but also identifies key challenges like fibre dispersion, corrosion resistance, and workability issues.The paper further discusses future directions where computational intelligence and data-driven optimization can revolutionize FRC development for resilient, sustainable underground infrastructure.The findings aim to guide performance-based design strategies that enhance durability, safety, and environmental compatibility in tunnel lining engineering.