Total Volume Change Measurement of Unsaturated Soil in Triaxial Tests: A New Approach

Abstract

Abstract In the evaluation of unsaturated soil behavior in the laboratory, it is required to measure the total volume change of triaxial soil specimens. This, however, is not an easy task, with setups proposed in the literature being quite expensive or presenting variable setbacks. In this context, this article presents a new, reliable, cheap system to estimate the total volume change of the soil in unsaturated conditions in triaxial tests. To do so, a double-chamber triaxial cell was developed, with the inner cell connected to an air-tight container subjected to the same cell pressure and positioned on a precision analytical scale. The measure of the total volume change is given by the mass of water entering or leaving the air-tight container. After calibration, the system was tested under consolidation using saturated soil samples. Comparing the conventional change in water volume of the saturated specimen with the variation of the total volume obtained through the developed system, a maximum difference of 0.01 cm3 is obtained, which equals only 0.01 % of the specimen volume. The effects of temperature and of cell pressure variation, which might occur during the saturation of unsaturated specimens in conventional triaxial tests, are also presented and discussed.