Experimental Study on Prefabricated Steel Fiber-Reinforced Concrete Casing Arch Method for Strengthening Cracked Lining in Confined Spaces

Increasingly, research indicates that steel fibers can significantly enhance the engineering properties of mortar and concrete; however, few studies have examined their impact on the reinforcement of in-service tunnel linings within sleeve arch structures. In this study, a series of 1:2 scale experiments were conducted using a specialized loading device to compare the reinforcement performance of steel fiber-reinforced concrete sleeve arches and traditional reinforced concrete sleeve arches on prefabricated cracks with depths of 1/3 and 2/3 of the lining thickness. The experimental results were validated using numerical simulations. The results indicate that under the same load, when reinforcing components with 2/3 prefabricated cracks, the maximum compressive strains for steel fiber-reinforced and reinforced concrete sleeve arches were −852 με and −985 με, respectively, and the maximum deflections were 3.57 mm and 5.48 mm. Composite sleeve arches of both materials provide a certain degree of reinforcement to linings with varying damage. The reinforcement performance of steel fiber-reinforced concrete sleeve arches is superior to that of traditional reinforced concrete sleeve arches, with particularly significant reinforcement for linings with 2/3 prefabricated cracks. Numerical simulations have shown that the stress in reinforced concrete at the concentrated stress regions is 16.15%, 6.01%, 12.68%, 36.62%, and 4.82% higher than that in steel fiber-reinforced concrete, respectively, thereby validating the reliability of the experimental results. Therefore, this study recommends the application of steel fiber materials in sleeve arches to achieve superior maintenance and reinforcement, addressing cracking issues in in-service tunnel linings and thereby improving the safety and durability of these structures.