Undrained analysis of ground reaction curves for deep tunnels in saturated ground considering the effect of ground reinforcement

This paper investigated the undrained responses for deep circular tunnels with reinforcement in saturated ground analytically. An idealized model of an axisymmetric tunnel with an initial hydrostatic stress field was proposed. Plane-strain analysis was performed to obtain the ground reaction curves by gradually decreasing the internal support pressure from the initial stress to zero after tunnel excavation. The reinforced ground by full-face grouting was assumed as an equivalent circular region to consider the reinforcement effect. Both of the natural ground and the reinforced ground were assumed as the elastic-perfectly plastic materials satisfying the Mohr-Coulomb yield criterion. The proposed model was used to estimate the efficiency of the reinforcement parameters for a deep underwater tunnel. The analytical results were validated by the numerical results. Results show that as the decrease of internal support pressure, the plastic zone may firstly appear not only in the reinforced ground or in the natural ground, but also appear in the two zones simultaneously. Six forms of different plastic zone distributions were categorized. The ground reaction curve for each form was analyzed and 8 critical support pressures were obtained in the unified theoretical framework for the specific boundary conditions. The present model has advantages in undrained analysis of ground reaction curves for deep tunnels in saturated ground considering the effects of ground reinforcement compared with the classical model.