Automated triaxial apparatus for testing unsaturated soils

Three automated triaxial testing systems developed to study the mechanical-hydraulic behavior of unsaturated soils are described in detail. The apparatus and the associated techniques were designed to obtain reliable and accurate measurement and control of matric suction, measurement of volumetric change and to perform static and dynamic stiffness measurements for soil samples under unsaturated conditions. Results for a silica silt are presented to illustrate the type and quality of data obtained with the techniques developed. An additional feature of the apparatus is that it is possible to obtain, for the same soil sample, both the stress-strain curve and soil-water retention curve at any degree of saturation.