A new thermo-mechanical model for structured soil

Although thermo-mechanical behaviour of soil is strongly affected by structure, as far as the authors are aware, none of the existing constitutive models has incorporated structure effects. Consequently, the thermo-mechanical behaviour of a soil with various structures (e.g. reconstituted, intact and recompacted specimens) cannot be captured by using a single set of parameters. In the present study, a new thermo-mechanical elastoplastic model is proposed for structured soil. The model is appropriate for predicting soil behaviour under one-dimensional and triaxial stress conditions. It is assumed that soil structure affects thermo-plasticity through three different mechanisms: (a) structured soil (e.g. intact and recompacted specimens) has a larger preconsolidation pressure than the corresponding reconstituted soil at a given temperature, stress and density condition; (b) thermal softening (i.e. the reduction of preconsolidation pressure with increasing temperature) of structured soil is smaller than that of reconstituted soil; (c) degradation of soil structure contributes to plastic thermal strain. To verify the new model, it is applied to simulate the behaviour of reconstituted, intact and recompacted loess (low-plasticity clay) under cyclic heating and cooling. Experimental results and model predictions are well matched. It is evident that, with a single set of parameters, the proposed model is able to capture cyclic thermal behaviour of a soil with various structures.