Hypoplastic interface models for fine-grained soils

Contact descriptions for interfaces between structural elements (e.g. piles, anchors and tunnel-linings) and soils are widely used in geotechnical engineering. Most of these constitutive interface models, developed for sands, consider 2D conditions. For clays, only a limited number of 3D interface models exist. In this paper, the fine-grained continuum models based on hypoplastic theories are adapted for the constitutive modelling of fine-grained interfaces. To this end, we develop a general approach to convert the existing continuum soil models into an interface model adopting reduced stress and strain-rate vectors and redefining tensorial operations in such a way that the formulation of the existing continuum models can be used without much modification. The hypoplastic Cam-clay and the explicitly formulated hypoplastic models are adapted to model the interface behaviour. In addition to the reduced stress and strain tensor formulations, we introduce an additional variable reducing the strength and stiffness of the interfaces when compared with the strength and stiffness of the soil. For verification, experiments in constant volume and constant normal stress conditions have been simulated. A comparison of the available experimental data from the literature and the simulations is presented. It is shown that the new hypoplastic interface models can describe a number of important phenomena of clay-structure interfaces. Copyright (C) 2016 John Wiley & Sons, Ltd.