Analysis of deep tunnels and shafts driven at constant rate

An efficient numerical method for circular tunnels driven in homogeneous and isotropic media is described, under the assumption of a constant rate of advance. The procedure allows in a reference moving with tunnel face, to calculate directly the steady stresses and strain states, using an adequate algorithm, and expanding the solution into Fourier’s series in the angular direction perpendicular to tunnel axis. The performance of this method is estimated by comparison with a plane strain analysis in a section far from the front face. Then the method is used for a critical check up of usual assumptions for approximate plain strain approaches as extension of the so called “Convergence Confinement method” to non isotropic geostatic stresses.