Multilaminate models for numerical simulation of tunnel excavations according to NATM

Excavation of tunnels with low overburden under unfavourable geological conditions can lead to extensive shear band formation in the ground which can even cause the collapse of the structure. In this paper a constitutive model embedded within the Mulilaminate framework is presented which is able to capture the mechanism of strain localisation and the formation of shear bands. The model includes deviatoric hardening in the pre-peak range and strain softening in the post-peak behaviour. Application to numerical simulations of a biaxial test and a shallow NATM tunnel excavation in staged construction sequence demonstrates the potential of the model to predict shear band formation and possible failure mechanisms with sufficient accuracy for practical problems.