Numerical investigation on failure characteristics of concrete lining in deep tunnel subject to oblique incidence of stress waves

In response to the instability and failure of concrete linings in deep tunnels due to obliquely incident stress waves from mining disturbances, this study investigates the failure characteristics of concrete tunnel linings under varying wave incidence angles (0°, 15°, 30°, and 45°) using numerical modeling with PFC2D software. The model applicability is verified by stress wave propagation theory and spalling tests. Results demonstrate that under blast loads, failures predominantly occur in the concrete lining rather than the rock mass. Concrete linings effectively reduce blast damage to the surrounding rock and maintain stability. Vertical stress wave incidence causes the most severe damage to the concrete lining, whereas the least damage occurs at a 45° angle. The concrete tunnel lining failure is primarily caused by P-wave. When P-wave is large enough, the S-wave generated by oblique incidence make the tensile crack expand, and lead to second damage to concrete tunnel lining. As incident wave energy increases, concrete lining damage worsens, followed by rock spalling. The strain energy in concrete tunnel lining accumulates with increasing burial depth, resulting in more cracks in concrete tunnel lining under the action of the same stress wave. Thus, even small blast loads can severely damage deep-buried concrete tunnel linings.