Design of deep rock tunnels using hyperstatic reaction and convergence confinement methods

Tunnel lining is usually installed with delay behind the tunnel face excavation, which requires that a displacement is considered at the tunnel boundary before the support structure installation. This delayed installation comes with a release and redistribution of stress in the rock mass. Internal tunnel lining forces significantly rely on the stress relaxation process taking place in the rock mass surrounding the excavated tunnel. One of the difficulties when designing tunnel supports is, therefore, to analyse the rock–support interaction considering the tunnel lining convergence caused by the stress redistribution. Here, a simple and effective calculation process based on the combination of two methods, the hyperstatic reaction method (HRM) and convergence confinement method, is presented to analyse the interaction of rock mass and support structure. The rock mass is assumed to obey the Hoek–Brown criterion. The stress release is also taken into consideration. The present method is validated by comparing results of the HRM in terms of tunnel lining forces against the analytical ones. Thereafter, the effect of the stress release coefficient, the tunnel depth and the Hoek–Brown criterion parameters (the geological strength index and σ_ci) on the lining internal forces are presented and discussed.