Abstract: At present, most of the elastoplastic constitutive models for unsaturated soils are verified by using test results of unsaturated compacted soils. In situ, other types of the soils, such as alluvial soils, are often in the unsaturated states. Hence, it is necessary to study if the existing elastoplastic models for unsaturated soils are suitable for unsaturated alluvial soils. A series of triaxial tests on unsaturated Shanghai layer ③ soil were performed with suction being controlled. By using an elastoplastic model proposed by the first author for predicting the hydraulic and stress-strain behaviour of unsaturated soils, the model predictions were made on the tested conditions. Predicted results are compared with those obtained from drained triaxial compression tests on unsaturated Shanghai layer ③ soil during shear loading. The comparisons indicate that the model can reproduce the hydraulic and mechanical behaviours of undisturbed Shanghai soft clay very well. Therefore, the model is not only applicable to unsaturated compacted soils, but also is suitable for unsaturated alluvial soils.

Key words: unsaturated soil, elastoplastic model, triaxial compression test, Shanghai soft clay, stress-strain relation