Design of Deep Rock Tunnels combining the Hyperstatic Reaction and Convergence Confinement methods

Abstract

Tunnel lining is usually installed with delay behind the tunnel face excavation, which requires that a displacement has to be 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 analyze the rock-support interaction considering the tunnel lining convergence caused by the stress redistribution. In this study, a simple and effective calculation process based on the combination of two methods, the Hyperstatic Reaction Method (HRM) and Convergence Confinement Method (CCM), is presented to analyze 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 in the present method. 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, of the tunnel depth and of the Hoek-Brown criterion parameters (the Geological Strength Index (GSI) and σci), on the lining internal forces are presented and discussed.