###### Abstract  
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 \(-852\)\(\mu\)c and \(-985\)\(\mu\)c, 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. highway tunnel; lining reinforcement; prefabricated thin arch; steel fiber concrete; mechanical property +
Footnote †: journal: Applied sciences  
0000-0002-4300-3300][PERSON]  
0000-0002-3300-3300][PERSON]  
0000-0002-3300-3300-3300-3300-3300-3300-33000-3300-33000-33000-33000-33000-33000-33000-33000-33000-33000-33000-33000-33000-33000-33000-33000-33000-33000-33000-33000-33000-33000-33000-33000-33000-33000-330000-33000-3300 the Dugong Ling Tunnel [5; 6] in Shanxi Province, China, developed numerous cracks during operation, with fractures ranging up to 5 cm, 10 cm, and even wider. These cracks affect not only the tunnel's safety but also its structural stability. Since its inception, the Shiziya Tunnel on National Highway 209 has experienced issues like pavement cracking and lining collapse due to construction quality, posing significant security risks to tunnel traffic. The Wenchuan earthquake induced substantial deformations and severe lining cracks in the Guxi Tunnel, impacting its overall structural integrity. Furthermore, the lining cracks have led to deformations in the tunnel's rock mass, seriously jeopardizing its structural integrity and safety [7; 8]. To address the limitations of ordinary reinforced concrete's poor crack resistance and weak ductility [9], numerous experts and scholars have shifted their focus to steel fiber research. Introducing steel fibers into concrete significantly enhances a variety of engineering properties, including impact strength, toughness, tensile strength, bending strength, and fatigue strength, while also improving spalling resistance [10; 11; 12; 13]. Furthermore, incorporating steel fibers renders concrete more homogeneous, transitioning it from a brittle to a more ductile material. When cracks form in concrete, randomly oriented steel fibers help prevent the formation of micro-cracks, limit crack propagation, and enhance both the strength and ductility of the material. In light of the aforementioned examples, [PERSON] et al.