Excavation-induced zonal disintegration of the surrounding rock around a deep circular tunnel considering unloading effect

• A new non-Euclidean dynamic model is derived from the incompatibility deformation.
• The zonal disintegration mechanism of rock mass around a deep circular tunnel is revealed.
• The number and size of fractured and non-fractured zones are determined.

A new non-Euclidean dynamic model is proposed to investigate the zonal disintegration mechanism of isotropic rock masses around a deep circular tunnel subjected to dynamic unloading, in which the defect parameter R is introduced to describe effects of micro-defects on the deformation and failure of deep rock masses. On the basis of the deformation incompatibility condition, the non-Euclidean dynamic equation is established. Then Laplace transformation and inverse Laplace transformation theory are applied to solve the non-Euclidean dynamic equations. The stress fields are obtained from the non-Euclidean dynamic equations and the boundary conditions. The number and size of fractured and non-fractured zones are determined using the Hoek–Brown criterion. Numerical computation is carried out. It is found from numerical results that the number and size of fractured and non-fractured zones significantly depend on unloading rate, in-situ stress and dynamic mechanical parameters of deep rock masses.