Evaluation of the liquefaction potential of filtered tailings stacks by means of laboratory investigation

Filtered tailings are typically transported, placed, and compacted into embankments to form unsaturated, dense stacks. For economic reasons, these stacks must be raised with maximum productivity and minimal possible cost. Achieving this may involve using thicker compaction layers than in conventional embankments, along with employing bulldozers and trucks in place of rollers. However, increasing the layer thickness often leads to lower compaction within individual layers. To assess the geotechnical behavior of filtered tailings, laboratory testing was conducted on three layers of varying thickness within a test embankment. The results were evaluated within a critical state soil mechanics framework to assess the susceptibility of filtered tailings to static liquefaction. The degree of compaction (DC) was found to play a crucial role in determining the mechanical behavior of the filtered tailings. Samples with lower compaction levels showed a reduction in post-peak shear strength during undrained tests, making them more susceptible to liquefaction. The instability line was found to be sensitive to DC in all layers. The undrained brittleness index was also calculated to assess the potential loss of shear strength due to liquefaction. Therefore, ensuring adequate compaction is crucial to preventing the liquefaction of filtered tailings and maintaining the stability of the embankments.