Face Stability of Tunnel in Multi-stratum: Limit Analysis and Numerical Simulation

Under multiple-stratum conditions, the stability of the tunnel face must be maintained by a reasonable support pressure. Through the combination of theoretical analysis and numerical simulations, this study examines the stability of the tunnel face under multi-stratum conditions. Using software for finite difference numerical simulation, the stability of the tunnel face under multiple stratum conditions was examined. Four cases were used to determine the limit support pressures and failure zones of the tunnel face under multi-stratum conditions using various parameters. A simplified three-dimensional failure mechanism of multi-stratum conditions’ tunnel face was constructed, and the limit analysis upper bound theoretical model of the support pressure was obtained, based on the outcomes of numerical simulation and the limit analysis upper bound theorem. The findings showed that the limit support pressures of the three-dimensional failure mechanism are highly consistent with the outcomes of the numerical simulation in four cases. Besides, the final parameters sensitivity analysis focused on the tunnel face failure characteristics in the four cases. The parameters analysis suggests that the stability of the tunnel face can be enhanced by improving the stratum’s property or optimizing the tunnel section’s design.