A Model for Bonded Expansive Natural Soils and Rocks

In this paper, a constitutive model is presented to reproduce the behaviour of hard soils and soft rocks (HSSR) that exhibit an intrinsic expansive behaviour. The model focuses on argillaceous soft rocks and includes suction effects. The soil or rock is considered as a composite material made of an expansive argillaceous matrix and bonding agents that provide the effect of structure. Both components are endowed with their own constitutive law: Barcelona Expansive Model is used to represent the behaviour of the matrix; the damage model presented for the bonds. The model for the composite material is then derived on the basis of energy considerations. In a first part of the paper, the model is formulated. In a second part, its performance is described. Results show the capability of the model to reproduce features such as moduli and strength degradation during loading and elastic rebound above the initial compression line during unloading.