Elastic-plastic modelling of unsaturated soil using results from a new triaxial test with controlled suction

This paper examines the constitutive behaviour of a compacted highly plastic sand-clay mixture. Three series of tests evaluated components of a possible elastic-plastic constitutive model for unsaturated stress-strain behaviour. The tests examined the influence of suction on yield stress under external isotropic loading and the influence of suction on shear strength. The results examine the behaviour of highly plastic clay subjected to generalised (triaxial) stresses that include shear, isotropic and suction loading. The data represent an important new resource of information on a densely compacted, strongly expansive, sand-bentonite mixture that was loaded independently by external stresses and internal suctions. The suctions were also measured by sensors buried in the specimens. They have been interpreted in an elastic-plastic framework to produce values for some of the material properties needed for the model. The results and associated discussion provide new insights into the behaviour of unsaturated highly plastic clay materials.