FEM-based Contrastive Analysis of Lining Cracks Caused by Cavity behind Arch Shoulder in High-speed Railway Tunnels

The lining cracks and cavity behind lining are two major potential threats to the safety of high-speed trains. The cavity behind lining is considered not only the principal factor of threatening to the safety of tunnel structure,bus also the main cause of lining cracks in the high- speed railway tunnel.Concerning the lining fracture morphology under the conditions of a range of cavities behind the lining shoulder in the high- speed railway tunnel,the paper conducts a contrastive analysis with two different numerical simulation methods based on the stratum structure model,focuses on their theories and results of calculation,which are the XFEM based on the fictitious crack model and the CFEM based on the smeared crack model. The modeling results show that the cracks inside the secondary lining occur in the longitudinal boundary of the cavities adjacent to the tunnel vault and two circumferential through cracks appear along the circular boundary of the cavities to the primary lining. It also turns out that the XFEM can better describe the lining fracture morphology,such as the strike,length and crack laws,while the SOLID65 unit of ANSYS can offer a qualitative description to the fracture area of lining caused by the cavity behind lining. The mutual authentication and complementation can be more accurate to describe the geometric information and propagation rules of lining cracks and help the stress field analysis of lining fracture.