Numerical Analysis of Deep Tunnels in Viscoplastic Rock Mass Considering the Creep and Shrinkage of the Concrete Lining

Abstract

This paper aims to show, through numerical parameter analysis on a finite-element method with axisymmetry hypothesis, the long-term effect involving the creep and shrinkage of the concrete lining in deep tunnel problems. The excavation process is simulated by the deactivation and activation method. A viscoplastic constitutive model for the rock mass and an elastic and viscoelastic constitutive model for the lining are used in the software ansys. Perzyna’s viscoplastic constitutive model with an associated flow rule with von Mises yield surface is considered. The viscoelastic model is implemented in ansys using the customization feature. The shrinkage is given by the CEB-FIP MC90 formulation and the creep part is modeled through a Generalized Kelvin chain, according to the solidification theory of Bažant and Prasannan, whose parameters are adjusted with the creep function of the CEB-FIP MC90. Compared with an elastic lining, the viscoelastic line showed a difference (in average terms), in the equilibrium convergence at the end of tunnel construction between 6% and 37%. This value increases to 8% and 72% in the long-term convergence.