Viscoelastic ground responses around shallow tunnels considering surcharge loadings and effect of supporting

Abstract

Tunnels in urban areas inevitably lie near the ground surface, and will be affected significantly by the loads on the surface. This study provides a new analytical approach to efficiently predict the time-dependent ground stresses and displacements induced by shallow tunnelling under initial stresses due to both gravity and surcharge loads. The viscoelasticity of the ground, inclination of ground surface, effect of support and its delayed installation, are all taken into account.The elastic potentials were first derived for tunnels subjected to boundary stresses induced by gravity, surcharge loads and tunnel supports, respectively. Based on the extension of correspondence principle, the time-dependent ground stresses and displacements were then provided analytically for any type of linear viscoelastic ground. The FEM analysis was performed to verify the analytical solutions, which demonstrates a well agreement between the analytical and numerical results. Additionally, by the qualitative comparison of surface movements and initial failure zone around tunnel between analytical solution and results from other numerical model of elastoplastic cases, it was proved that the analytical solution can predict the initial failure zone and can qualitatively provide the reliable ground deformations. Finally, a parametric study was carried out to find the influence of timing for support installation, the slop angle and the surcharge loads on stresses and displacements around tunnels. The proposed solutions provide a quick alternative method to predict the time-dependent ground responses of shallow tunnelling in rocks, or medium/stiff clays.