Enhancing Tunnel Fault-Resistance with Combined Seismic Joints and Steel–Polypropylene Fiber Concrete Linings

Tunnel engineering is frequently undertaken in complex geological environments, which present heightened risks during construction and operation, particularly in active fault zones. This necessitates the enhancement of fault resistance. This study investigates the combined application of Steel–polypropylene Fiber Concrete Linings and Combined Seismic Joints through numerical simulation using ABAQUS 2023 (Dassault Systèmes, France). The findings demonstrate that this combination significantly enhances the fault resistance of tunnel structures, exhibiting substantial synergistic effects. In comparison with the utilization of Steel–polypropylene Fiber Concrete Linings as a standalone measure, the maximum reductions in longitudinal tensile and compressive strain were found to be 40.1% and 46.7%, respectively. Furthermore, peak equivalent compressive and tensile plastic strains were reduced by 60.3% and 51.1%, and tensile and compressive damage by 4.9% and 17.3%. Further analysis reveals that the steel fiber aspect ratio and the content of both steel and polypropylene fibers have varying effects on suppressing different damage forms in tunnel linings. It is evident that an augmentation in the steel fiber aspect ratio most effectively suppresses plastic zone deformation, while an increase in polypropylene fiber content significantly reduces tensile strain and tensile damage. The optimal level of fault resistance performance is achieved when the steel fiber content is set at 1.90%, the aspect ratio is 60, and the polypropylene fiber content is 0.15%. Furthermore, the adjustment of the combined arrangement parameters enables tunnel structures to adapt more effectively to diverse operational conditions, thus providing flexible design solutions for practical engineering applications.