Tailings Dam Geotechnical Stability Improvement due to Flocculants Treated Fine Tailings Dewatering

The existence of fine and ultra-fine particles in mining tailings presents significant challenges to the geotechnical engineer when the tailings are used as construction materials to build a tailing dam. Tailings dewatering with flocculants before dam construction may be an effective method to alleviate or mitigate the stability problem. In this paper, the correlation between the geotechnical stability of flocculated and dewatered fine tailings and the flocculant type was investigated, from which the method to enhance the tailings geotechnical stability was developed based on the screening of effective flocculants. Three types of flocculants were applied to flocculate and dewater a mining fine tailing in a consolidation testing system, followed by geotechnical stability analysis via direct shearing testing and a case study by GEOSLOPE. Experimental results demonstrated the effect of flocculant type on geotechnical stability with the dewatering behaviors (dewatering rate and shear strength) of fine tailings strongly determined by the flocculant type and their dosages. The combination of the anionic and cationic flocculants provided the best performance in enhancing both the tailings dewatering and the geotechnical stability of tailing dams. Fundamental study results from measuring Zeta potential of fine-flocculant systems and scanning electron microscopy of flocculated fines revealed the mechanism behind the obtained test results that correctly selected flocculant types reduces repulsive force between the fines and the flocculant molecules, and also produce larger size of aggregates and larger void spaces that ensure effective dewatering, strength buildup and geotechnical stability of tailing dams.