Coal Preparation » Dewatering
Testing of fine coal materials in the unsaturated state, such as dewatered tailings, is inherently complex and requires precise measurement of both pore air and pore water volume changes to accurately evaluate the changing degree of saturation. The project focused on commissioning laboratory testing equipment to generate high quality data, in support of models for reliable mechanical characterisation of coal handling preparation plant wastes.
Two triaxial apparatuses available at the University of Newcastle were modified to incorporate reliable systems for measuring volume change and measuring/controlling soil suction in unsaturated DT and MPR specimens. Differential Pressure Transducers (DPTs) were installed in both triaxial devices for measuring sample's volume change. The axis-translation technique was also implemented in both triaxial systems for measuring/controlling soil suction. By doing so, suctions between 0 < s < 1400 kPa may be applied which are appropriated for the suction range expected in unsaturated DT and unsaturated MPR materials.
A total of seventeen triaxial tests were completed on unsaturated DT and MPR specimens. Six additional triaxial tests were completed on fully saturated DT and MPR samples. Tests on DT and MPR specimens were carried out on statically compacted samples. It is important to note that the compaction conditions selected for the suction-controlled testing in this project were chosen to provide repeatable soil samples with relatively high density for triaxial testing instead of attempting to demonstrate the liquefaction potential of DT and MPR materials.
Additional aspects of the behaviour of DT and MPR materials are included in this report. This includes the Water Retention Curve (WRC) which describes the water retention characteristics of DT and MPR materials upon drying and wetting paths.
The results demonstrate the benefits of unsaturated triaxial testing for proper characterisation of Coal handling preparation plant wastes.