Zonal disintegration mechanism of cross-anisotropic rock mass around a deep circular tunnel under dynamic unloading

A mechanical model is proposed to investigate zonal disintegration mechanism of cross-anisotropic rock masses around a deep circular tunnel subjected to dynamic unloading under hydrostatic pressure condition as well as the total elastic stress-field distributions. Effects of unloading rate and dynamic mechanical parameters on the zonal disintegration phenomenon of the surrounding rock masses around a deep circular tunnel as well as the total elastic stress field distributions are taken into account. Numerical computation is carried out. The location, number and size of fractured and non-fractured zones are determined using the Hoek–Brown criterion. It is found from numerical results that the location, number and size of fractured and non-fractured zones significantly depend on unloading rate and dynamic mechanical parameters of deep rock masses.