Unified bounding surface model for monotonic and cyclic behaviour of clay and sand

Abstract

This paper presents a constitutive model enabled to simulate monotonic and cyclic behaviour of clay and sand in a unified framework. The bounding surface concept has been utilized to predict a smooth transition from elastic to plastic state of the soil. A new dilatancy relation is proposed to capture the volumetric behaviour of sand and clay in a unified manner. Moreover, closed hysteresis loops and accumulation of the plastic strain during cyclic loading have been regarded appropriately by transmitting the similarity centre of the loading and bounding surfaces in the stress space through a kinematic hardening rule. Furthermore, in order to improve the accuracy and convergence property of the model, an implicit integration scheme is introduced. Finally, the accuracy and performance of the model are verified using several experimental data from the literature. Both drained and undrained behaviours under monotonic and cyclic loading for sand and clay are considered, and the characteristic features of the behaviour are captured.