Comments on use of the Barcelona Basic Model for unsaturated soils

The paper discusses some aspects of the Barcelona Basic Model (BBM), which is one of the most widely used elasto‐plastic models for unsaturated soils. In addition to modelling those unsaturated soils where the collapse potential increases with increasing net stress (as envisaged by the original authors), the BBM can also be used to model soils where the collapse potential decreases with increasing net stress, by selecting suitable values for the model parameters r and p c . A practical procedure is suggested for selecting a value for the important model parameter p c from laboratory test data. Problems with use of the BBM are discussed, including the difficulty of correctly matching the locations of the normal compression lines for different values of suction and the possibility of non‐convexity of the yield curve.