Some observations on numerical modelling of tunnelling-induced soil movements by a displacement-controlled technique

Predicting the impact of tunnelling-induced soil movements on adjacent existing infrastructures and buildings requires appropriate numerical tools. Finite element modelling has been extensively used, often in combination with the classical Mohr-Coulomb constitutive law for the soil and simplified displacement-controlled techniques to simulate the tunnel construc-tion. While the applicability of this approach has been thoroughly investigated in the past with reference to the surface subsidence trough, its performance for the prediction of the subsurface displacement field has not received enough attention so far. In this paper, the results of a parametric study employing a displacement-controlled technique for the simulation of single and twin tunnelling are presented, with a focus on the influence of tunnel geometry, tunnel volume loss, soil material parameters and drainage conditions. Numerical results indicate that the predicted soil movements become not accurate for relatively large tunnel volume losses and low soil stiffness, the displacement field being characterised by vortex-like patterns on the upper lateral sides of the tunnels, especially when twin tunnels are excavated in sequence in the numerical analyses.