Influence of linings on stress and deformation in rock around tunnels

Abstract

Stress distribution and deformation in rock around lined tunnel openings subjected to internal pressure are investigated by using plane strain finite element analysis. Two typical tunnel cross- sections, in the forms of an elliptical and a horse-shoe shaped tunnel, are considered with varying thicknesses of concrete linings; material behavior is assumed to be isotropic linear elastic, and analyses are done using typical elastic material parameters to represent a particular type of rock and the concrete. Variation of major and minor principal stresses in the rock medium with increasing liner thickness and distance from the tunnel face is presented for both tunnel shapes. The influence of the lining thickness on the deformation (displacement) characteristics at selected locations in the rock medium is illustrated. The results show the general trend that stresses and deformations in the rock medium decrease with increasing liner thickness, but the effect of the liner thickness depends on the stress or displacement quantity being investigated as well as the shape of the tunnel. Thus an optimal liner thickness has to be estimated as a compromise between economy and effectiveness.