Influence of rock mass creep on tunnel loading

Abstract

Rock mass creep in tunnelling through weak rock masses under high overburden may lead to the potential development of significant convergence. Should this convergence be restrained by a rigid support shell, tunnel loading tends to increase. Although, such increase could be significant, it is often not taken into account in design, due to uncertainties in the calculation procedure. This paper proposes a simplified approach for estimating the additional creep loads on the lining of circular tunnels excavated in one phase. This is achieved by performing a parametric set of 2D numerical analyses with the finite element code ABAQUS. The rock mass is modeled as an elasto-plastic material yielding according to the Drucker-Prager criterion, with time-dependent characteristics described by the Singh-Mitchell creep model. The time-dependent behaviour is initially formulated upon the assumption of a new set of parameters. Typical ranges of these parameters are estimated using creep experiments from the literature.