THE EFFECT OF VOID RATIO, MOISTURE CONTENT AND VERTICAL PRESSURE ON THE HYDROCOMPRESSION SETTLEMENT OF COPPER MINE TAILING

Copper mine tailing (CMT) has the potential to be used as embankment material but this waste material contains plasticity. Soils containing plasticity are highly reactive to any form of liquid and considered to have greater compressibility when exposed to water. As an embankment material, CMT is susceptible to different environmental condition which can cause significant settlement. One possible cause of volume loss is the compression due to wetting or hydrocompression. This study aims to determine the consolidation properties and hydrocompression settlement of waste materials with plasticity like copper mine tailing when used as embankment material. One-dimensional consolidation tests were performed on reconstituted specimens. The obtained consolidation properties indicate that CMT is very slightly compressible under over-consolidated condition to moderately compressible under normally consolidated condition. The hydrocompression settlement of CMT in relation to initial void ratio, moisture content and vertical pressure was investigated. The hydrocompression settlement increases with increasing pressure until the preconsolidation pressure is reached, then decreases with pressure beyond the preconsolidation pressure. Samples with lower density and initial water content less than its optimum exhibit greater hydrocompression settlement. The determined hydrocompression strain in every condition is less than 5% which means that CMT has a degree of collapsibility classified as low to negligible despite of having plasticity. CMT when used as embankment materials should be prepared with initial moisture content slightly more than its optimum, it should be in its very dense condition and preloaded with vertical stress more than its preconsolidation pressure to make hydrocompression strain negligible.