Influence of Wavelength-to-Excavation Span Ratio on Dynamic Failure Characteristics of a Deep-Buried Tunnel Subjected to Disturbance

Deep-buried structures are frequently and inevitably subjected to aperiodic perturbation during their life circle, resulting in damage to the rock mass surrounding the structures under the coupled action of excavation-induced local stress and dynamic perturbation. The investigation presented in this paper concentrates on the analytical and numerical dynamic responses around an unsupported deep-buried tunnel subjected to blasting disturbance with different wavelength-to-excavation span ratios (lambda/D). Based on the complex function theory, the integral transform and its inversion, the elastic responses around the tunnel are obtained theoretically. Then the corresponding elastoplastic counterparts are explored using a self-developed code: elastoplastic cellular automaton. The analytical results indicate that Poisson's ratio, the ratio of total time for blasting load to rising time, and lambda/D have a significant influence on the distributions of dynamic stress concentration and velocity vibrations. Moreover, the numerical results reveal that tensile failure and the compression-shear counterpart are major damage mechanisms for the rock mass when the wavelength is less than the excavation span, while the compression-shear failure is major damage mechanism when the wavelength exceeds the excavation span. The analytical and numerical results can provide guidance for the support of deep-buried rock tunnels.