On the 3D numerical modelling of the time-dependent development of the damage zone around underground galleries during and after excavation

This paper presents a 3D numerical simulation of the mechanical behaviour of deep underground galleries with a special emphasis on time-dependent development of the Excavation Damage Zone (EDZ). The rock mass behaviour is modelled by a damageable viscoplastic constitutive law in which both viscous and damage parameters are taken into account. Finite-element analysis investigates the evolution of near-field stresses, progressive development of the damage zone as well as delayed displacements during the sequential construction process of the gallery. The influence of the orientation of in situ stresses with respect to the gallery axis is also highlighted. Moreover, the effect of a support system is shown to reduce the damage zone and the displacements around the gallery. The conclusion provides some guidelines for a computer aided analysis of the design of underground openings.