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

Abstract

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 (λ/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 λ/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.