Mechanical behaviors of hybrid fiber-rebar reinforced concrete lining under ground surcharge loads—3D numerical simulation combined with full-scale test

Traditional reinforced concrete (RC) segments used in shield tunnel linings face limitations in crack resistance and durability, while hybrid fiber-reinforced concrete (HFRC) offers a promising solution to enhance its long-term performance. However, significant knowledge gaps remain regarding the application of HFRC in conjunction with steel reinforcement rebars to improve the structural performance of segmental linings. This study examines the mechanical performance of tunnel linings constructed using four types of segments, namely traditional RC, unreinforced HFRC (UR-HFRC), partially reinforced HFRC (PR-HFRC), and fully reinforced HFRC (FR-HFRC). A refined three-dimensional finite element model (3D FEM) was developed, incorporating a constitutive model for HFRC derived from laboratory tests. The accuracy of the 3D FEM was validated against full-scale load test results. Key findings include: the FR-HFRC segment ring demonstrates the highest ultimate bearing capacity and enhances subsequent stiffness during the hardening phase compared to RC segments. In reinforced segments (RC, PR-HFRC, FR-HFRC), rebars effectively mitigate cross-sectional yielding; however, this advantage comes at the cost of successive plastic hinge formation at segment joints during ultimate failure. Both bolts and reinforcement play a crucial role in load distribution, with HFRC enhancing the synergy between bolts and segments, thereby reducing reinforcement stress levels. Nevertheless, the stress in the reinforcement rarely reaches the yield point, suggesting potential underutilization in certain cases. By optimizing material configurations, HFRC can potentially offer an efficient and cost-effective solution for tunnel lining construction.