Peridynamics simulation of shotcrete lining damage characteristics under freeze-thaw cycles in cold region tunnels

Abstract

An improved ordinary state-based peridynamic (OSBPD) model is proposed to study the damage evolution of shotcrete lining under freeze-thaw cycles (FTCs) in cold region tunnels. The fracture criterion of bond in PD model is modified by introducing freeze-thaw damage function and by considering the difference of mechanical behaviors of shotcrete under tension and compression. In combination with material point dormancy method, a PD model is constructed to simulate the excavating and supporting process of tunnels in cold regions. In the numerical implementation, a global convergence criterion is employed to accelerate the solution convergence. For comparison, a finite difference method (FDM) model also is established to simulate the same excavating and supporting process. It shows that the results of the improved OSBPD model are consistent with that of the FDM, and the improved OSBPD model is more efficient. With the proposed model, some influence factors, such as tunnel buried depth, surrounding rock grade and section shape, on damage evolution of the lining structure under FTCs are originally investigated. The results demonstrate that accumulated freeze-thaw damage at the arch foot is more severe while buried depth increasing or rock elastic modulus decreasing.