2024 Volume 5 Issue 2 Pages 74-86
This paper presents an isotropic-confining triaxial system particularly designed for three-dimensional (3-D) volume change measurement of unsaturated compacted bentonite when being wetted. The specimen size was set to be small (diameter less than 30 mm and height of 10 mm) to reduce testing duration, which, as a result, introduces many difficulties to design the apparatus and to measure volume change with sufficient accuracy. In the triaxial system, two volume change measurement methods were applied, local deformation measurement by using laser displacement transducers (LDTs) and global measurement method with a differential pressure transducer (DPT) to monitor volume change of cell water. Another two methods to measure final volume change, the final water content method and the pycnometer method, were also newly proposed. Technical details to improve measurement accuracy were described. Testing results suggest that the measurement accuracy in terms of absolute volume change variation was of 0.09-0.12 ml, which is better than many currently available techniques.
