An elastoplastic shear-fracture model for soil and soft rock

Abstract

An elastoplastic shear-fracture approach to the constitutive behaviour of soil and soft rock is proposed. The model is an extension of critical state soil mechanics in that it adopts the Hvorslev-modified Cam clay (MCC) idealization as its starting point. However, once shear band localization failure occurs, ductile elastoplastic fracture may follow. When the material is sufficiently brittle, as in the case of hard, partially saturated soil or soft rock, tensile elastic fracture occurs after peak stress. A transitional state can also occur whereby tensile elastic fracture is followed by elastoplastic shear fracture. In this way, the model may, in principle, address the entire range of soil behaviour, from the 'wet' side of critical state to that of a hard consistency, including soft rock. In the present discourse, the key features of the proposed model will first be outlined. The example of brittle elastic fracture will then be dealt with, in order to demonstrate the application of the proposed model.