Research on the Mechanical Properties of Multi-Scale Polypropylene Fiber Reinforced Concrete Secondary Lining

When lining cracking, water leakage, corrosion and other diseases occur in operating tunnels, the treatment of lining diseases should not only consider the stress condition of the supporting structure, but also the performance of the supporting materials. Based on a tunnel secondary lining replacement project, a field test of the secondary lining of Multi-scale Polypropylene Fiber Reinforced Concrete (MPFRC) was carried out. The long-term observation and data collection were carried out on the lining strength, tunnel appearance, contact pressure between the primary support and the secondary lining, and concrete strain. The mechanical characteristics of the fiber-reinforced concrete secondary lining structure were studied. The results show that the strength of fiber to concrete is obviously improved under the condition of this ratio, and the compressive strength, split tensile strength and flexural strength have increased by 7.51%, 11.45% and 26.95%, respectively. Secondly, the maximum contact pressures of the ordinary concrete section and the fiber-reinforced concrete section are both at the arch foot, which are 282.63 kPa and 231.83 kPa, respectively. Thirdly, the strain amplitude of fiber-reinforced concrete is about 45.45% smaller than that of ordinary concrete, its strain curve is relatively flat, and the value is more stable. MPFRC enables the safety of lining structures to be enhanced. The research can provide a reference for the disease control of similar projects.