Rock-lining interaction calculations for tunnels excavated in Hoek-Brown rock mass considering excavation damaged zone

The excavation impact (e.g. due to Blasting, TBM drilling, etc.) induces an excavation damaged or disturbed zone around a tunnel. The presence of a damage zone around a tunnel boundary is of significant concern mainly with regard to safety, stability, costs and the overall performance of the tunnel. The damaged zone is essentially characterized by reduction in strength and stiffness, and increase in permeability. However, the dimensions of the restricted damaged zone is restricted. The effect of this zone is generally considered by a disturbance factor used for the whole rock masses. In this paper, the behavior of tunnels under different damage conditions is examined. In this regard, a fully analytical solution is proposed. The solution is presented for tunnels excavated in elastic–brittle–plastic rock masses with Hoek–Brown failure criterion. The damaged zone is assumed to have cylindrical shape with varied parameters. The results obtained by the proposed solution indicate that, the effects of the alteration of rock mass properties in the damaged zone may be considerable. In practice, the global damage induced by blasting is taken into account by using the damage factor D . In traditional methods, the blast damage factor D is applied to the entire rock mass surrounding the tunnel. This is a common modeling method which can greatly underestimate the strength and stability of the overall rock mass. In this regard, the result show that the blast damage factor D is more appropriate to be applied to the actual zone of damaged rock.