A double cell triaxial system for unsaturated soils testing

The presence of different pore fluids present in unsaturated soils (water and air) complicates the measurement of sample volume change. Since volume change of the air phase is difficult due to the compressibility of the fluid, it becomes necessary to measure sample volume change by measuring the change in volume of water in the surrounding triaxial cell. This paper introduces and assesses a new double cell triaxial cell developed by Wykeham Farrance. The design of the new triaxial system is similar to the Wheeler modified triaxial cell (Wheeler, 1988) but uses a glass inner cell wall, to avoid problems of absorption of water by Perspex. Furthermore, the cell has been designed to use a high capacity suction probe that can be fitted through the base pedestal. Issues of de-airing the cell and the accuracy of volumetric measurements that can be achieved are discussed in the paper