A new triaxial apparatus for studying stress effects on soil-water characteristics of unsaturated soils

Although it has been long recognized theoretically that mechanical stress (state) has influence on hydraulic properties such as water retention ability of unsaturated soils, relatively little experimental data have been reported in literature. In this paper, a newly developed stress and suction controllable triaxial apparatus for studying hydro-mechanical behavior of unsaturated soils is introduced and described. During a test, both isotropic and anistropic mechanical stresses and matric suction can be applied using the axis translation technique and volume changes of a sample can be measured. The application of the apparatus is illustrated by measuring the soil-water characteristics of an unsaturated expansive soil, with and without applying mechanical stress.