Analysis model for the excavation damage zone in surrounding rock mass of circular tunnel

The time dependent viscoelastic model is extended so that excavation lining process of tunnel can be taken into account, with special attention on the analysis of the excavation damage zone around a circular tunnel under hydrostatic condition. Combining the sliding crack model and equivalent crack method, an analytical model for the evolution of fractured zone in viscoelastic surrounding rock mass is proposed. The whole construction process of tunnel is divided into three stages, in which the stress and displacement are considered separately. Then, the time dependent evolution of EDZ is implemented in a short computation algorithm, in which both extent and direction of fractured zones are determined. It is key important for the settlement of rock bolt. Through sensitivity analysis of parameters, the dependence of EDZ on time, excavation velocity, structure of heterogeneous rock mass, lining supporting system, initial geostress and the radius of tunnel are determined. Because of the time dependence of rock mass, the failure and deformation behavior continue increasing, even if the excavation process finished. In addition, the displacement after lining is set up is far more than the one at the moment of excavation just finished.

► The whole construction progress, from excavation to lining, is taken into account.
► Both excavation velocity in and perpendicular tunnel section are considered.
► Not only the extent but also the direction of fractured zones is determined.