An isotropic hyperelasto-plastic model for soil with non-linear compressibility at low stress

The compressibility of soils at very low stresses is of significance in geotechnical engineering problems at the seabed such as cable trenching. At low stresses, compressibility of soil is highly non-linear and in a Critical State modelling framework, best expressed by a non-linear Normal Compression Line (NCL). To date very few constitutive models have incorporated this behaviour. The aim of this study is to capture the non-linear compressibility of clays via incorporating a compression index dependent on the current stress within the hyperplastic formulation of Coombs and Crouch [1]. The proposed formulation is consistent with the observed non-linear consolidation data of soils during one-dimensional consolidation at low stresses. The validity of this approach is examined using experimental data to demonstrate that the model with this added feature provides satisfactory predictions of uniaxial monotonic elasto-plastic behaviour. The advantage of the proposed model is that the non-linear compressibility of soil may be calibrated from a standard oedometer test and then used to predict mechanical properties of soils obtained from tests such as, uniaxial loading-unloading tests.