Steel Fiber Reinforced Concrete: A Systematic Review of Usage in Shield Tunnel Segment

With the advancement of tunnel construction, the load-bearing capacity of shield tunnel segments is diminishing, while issues of deformation and fissuring are becoming more conspicuous, posing direct threats to structural integrity and functionality. Steel fiber reinforced concrete (SFRC) is considered a prevalent material, endowed with high strength, excellent crack control, fracture toughness, and remarkable economic advantages. This paper surveys the state-of-the-art research on SFRC, systematically encapsulating key aspects regarding its composition, attributes, methods of segment reinforcement, constitutive models for SFRC segments, and performance enhancements of SFRC segments. By optimizing steel fiber content, aggregate preparation, and selection of chemical admixtures, the mechanical performance of SFRC can be augmented, among which the aspect ratio (l/d) and volume fraction (Vf) of steel fibers exert the most significant influence. Compared with conventional reinforcing materials, SFRC possesses benefits of low cost, uncomplicated fabrication, and superior durability. As a heterogeneous multiphase composite, SFRC exhibits high strength, stiffness, and excellent crack resistance, which can amplify the load-bearing capacity and deformation resistance of the segments, defer damage inception, and thereby enhance the safety and durability of tunnel-lining segments. This study assists in redressing the deficiencies of current shield tunnel segment reinforcement technologies and further facilitates the extensive employment of SFRC in tunnel segment strengthening and restoration.