A multi-cell extension to the Barcelona Basic Model

One of the sources of discrepancy between laboratory observations and the predicted behaviour of unsaturated soil (by many existing constitutive models) is the sharp transition between the elastic and elasto-plastic regimes exhibited by the latter but not the former. Such a transition is present in, for example, the Barcelona Basic Model. This paper suggests that by using the water retention curve and a multi-cell approach it is possible to overcome this limitation. The proposed enhancement may be incorporated relatively easily into many existing elasto-plastic models for unsaturated soils without addition of any new constitutive variables. The introduction of the algorithm presented here can improve the predictions in pre-yield states. In this paper the multi-cell approach has been implemented into the Barcelona Basic Model (BBM). The algorithm is described in detail using an illustrative stress path that involves hydrostatic compression, drying and wetting. The paper closes with a comparison of the modified model with the original BBM.