Numerical modelling of tunnel excavation in soils using the Multilaminate Model

Finite element analyses of a tunnel excavation with low overburden are presented utilizing a constitutive model embedded within the framework of the Multilaminate Model. It incorporates deviatoric hardening plasticity in the pre-peak range and a simple strain softening formulation for approximating the post-peak behaviour. Staged construction sequence of the tunnel is simulated by modelling excavation of top heading, bench and invert. It is demonstrated that the mechanism of strain localization and shear band formation which may lead to the collapse of the structure can be captured reasonably well and with sufficient accuracy for practical problems. Furthermore it is shown that displacements under working load conditions are qualitatively in good agreement with observations made in practice.