Zorzal, R, Mansur Gomes, M & Pinheiro, J 2020, 'Tailings Geotechnical Characterization from Cuiabá Mine to Support a Dry Stacking Disposal Design in Cuiabá Dam', in H Quelopana (ed.), Paste 2020: 23rd International Conference on Paste, Thickened and Filtered Tailings, Gecamin Publications, Santiago, https://doi.org/10.36487/ACG_repo/2052_55
(https://papers.acg.uwa.edu.au/p/2052_55_Zorzal/)
Abstract: The main advantages of Filtered Tailings (FT) are related to water reduction in tailings disposal when compared with other methods, once it allows the geomaterial to be disposed close to optimum water content, thus allowing a better tailings compaction, and consequently increasing tailings shear strength for both drained and undrained conditions. Another advantage is the significant amount of water recovery during ore beneficiation process, especially in mining projects in dry areas.
However, as the main FT disposal designs in operation worldwide are located in drier regions, this Tailings Storage Facility (TSF) method may be a challenge for tropical regions as they generally present a positive water balance. As a consequence, tailings can be saturated and present contractive behaviour if the disposal has not been made properly and compaction has not been well controlled. Thus, this paper presents the geotechnical characterization of tailings generated in Cuiabá Mine Site to support the applicability of FT technique in dry stacking design (compacted FT disposal for buttressing downstream of the dam embankment and across the tailings reservoir). It included seismic piezocone – SCPTU tests of tailings disposed in the reservoir and laboratory tests with disturbed tailings samples at different void ratios to evaluate the effect of compaction effort on the geotechnical parameters of FT to support this new TSF method.
The main results obtained from the geotechnical tests to support the design have shown: (i) tailings inside the existing TSF have presented contractive behaviour under high strain conditions and undrained strength ratio of 0.21; (ii) the denser the tailings, the higher the undrained strength ratio and the total friction angle. Besides, the contractive or quasi-steady state behaviour obtained to higher void ratios changed to quasi-steady state or strain-hardening behaviour with density increase; and (iii) the tailings critical state friction angle was closed to 32º.