Long-term Performance of High-speed Railway Tunnels under Dynamic Train Loadings: Impact of Surrounding Rock Masses on Structural Deformations

With the rapid development of high-speed railway networks, a significant number of tunnels have been constructed in fractured rock masses. Ensuring the long-term stability and safety of these tunnels throughout their 100-year service life requires a comprehensive assessment of their structural performance under repeated dynamic train loadings, accounting for ground-tunnel interactions. Structural deformations in rock tunnels can result directly from long-term dynamic loading induced by train movements, or indirectly from rock mass degradation and shear displacement along discontinuities. In this study, we employ the distinct element method to develop a two-dimensional numerical model that captures these complex interactions. Rock mass degradation is simulated using a logarithmic function, while shear displacement along discontinuities is governed by a slip-weakening law. Within this framework, we systematically investigate the effects of rock mass deformation and degradation on tunnel performance under varying degradation rates (Rd) and slip-weakening distances (Dc). Our results reveal that higher Rd values and smaller Dc values lead to increased shear displacements and enhanced rupture propagation, ultimately resulting in greater roadbed settlements and differential settlements between the two track rails. These findings have critical implications for the long-term safety and operational stability of high-speed railway tunnels in fractured rock masses.