Analytical Evaluation of Reinforcement Effect of PCM Shotcrete Method Using FRP Grid for Tunnel Maintenance

Degradation of lining concrete happens naturally in the tunnels that have been commissioned for several decades, which require proper maintenance to ensure their safety and effective functions. The PCM shotcrete method by means of FRP grid, with the characters of high strength, low weight, high workability, strong resistance to corrosion, and little influence on the existing structures, has been used in tunnel maintenance to repair the damaged lining of some aged tunnels. Up to now, the construction cases are still few, and the design routine of this method based on quantitative evaluation on the reinforcement effect has not been established. In this study, the shear bond strength and the shear stiffness of typical FRP grids are estimated by conducting direct shear test. Those parameters were input into a numerical model of tunnel to quantitatively estimate the displacement control effect of the FRP-PCM method. The experiment and numerical simulation results show that the FRP-PCM method has good reinforcement effect on tunnel lining.