Experimental investigation of the mechanical behavior of the steel fiber reinforced concrete tunnel segment

- A new full-scale test method for SFRC tunnel segments was proposed.
- The composite effects of steel fiber and steel rebar on mechanical behavior of SFRC tunnel segments were investigated.
- SFRC tunnel segments achieved significant reduction in crack width, providing serviceability advantages.
- SFRC improved the cracking load and toughness of tunnel segments.

The main objective of this paper is to investigate the composite effect of steel fiber and steel rebar on the mechanical behavior of full-scale steel fiber reinforced concrete (SFRC) precast tunnel segments fabricated for a subway tunnel in China. A new biaxial loading method was adopted to simulate the loading state of the tunnel segment. The experiment included an initial SFRC tunnel segment proposed for the project, and two other SFRC tunnel segments were employed for comparison. By comparing the test results, the static characteristics of the three segments, including the internal strain, deflection, neutral axis position and crack patterns were determined. The experimental results indicate that the combined used of steel fiber and steel rebar shows an enhanced effect by delaying the initial impact of cracking and increasing the limit of proportionality of the segments. Longitudinal rebar in the tensile region were more helpful in decreasing tension strain and deflection in the mid-span section than the steel fibers. However, steel fibers performed better in improving the cracking load, cracking resistance and toughness. Furthermore, the initial SFRC tunnel segment proposed for the project exhibited a significant reduction in crack width and satisfied the design criteria for load carrying ability and crack width. The combination of steel fiber and steel rebar indicates an optimal choice of reinforcement for a tunnel segment.