AIR VOLUME CHANGE MEASUREMENT IN UNSATURATED SOIL TESTING USING A DIGITAL PRESSURE-VOLUME CONTROLLER

One of the challenges associated with the testing of unsaturated soils is the measurement of air volume change induced by stress changes. Th is paper reports the results of an evaluation of a digital pressure-vo lume controller as an air volume change indicator. Effects of temperat ure, confined volume, and precompression of the measurement medium on the p-V characteristics and the device response were determined. The d evice was also used to measure air volume changes of unsaturated soil specimens undergoing isotropic consolidation and axial loading in cons tant water content tests in a triaxial cell. The results show that the controller performs satisfactorily as an air volume change measuremen t device. It also permits measurement of air volume change simultaneou sly with the implementation of the axis-translation technique, making it a versatile device in the testing of unsaturated soils.