Shear and dewatering behaviour of densified gold tailings in a laboratory simulation of multi-layer deposition

Abstract

Tailings may undergo desiccation stress history under varied climatic and depositional parameters. While tailings substantially dewatered prior to deposition may experience desiccation under the greatest range of climatic variation, even conventionally deposited tailings may desiccate in arid climates at lower rates of rise. Bench-scale research has shown that the stress history imparted by desiccation substantially improves strength in gold tailings. The present study further investigates this phenomenon by simulating multi-layer deposition of high-density tailings using a modular drying box, 0.7 m by 1 m in plan. The box is instrumented for directly measuring evaporation, drainage, water content, vertical volume change, and matric suction. Additional measurements included total suction at the surface as well as observations of crack development. The dewatering behaviour conforms to that predicted by previously published generic modelling, specifically that the presence of partially desiccated tailings initially accelerates, but then decelerates dewatering of fresh tailings. The shear behaviour of samples obtained using buried tubes and by driving thin-wall tubes into the multi-layer simulation are compared with shear behaviour of samples from bench-scale experiments. Shear strength of samples from the multi-layer simulation is independent of the sampling method, and shows higher strength than the bench-scale samples. The higher strength may be due to the greater number of wet–dry cycles or other age-related processes.

2013 Colloquium of the Canadian Geotechnical Society: Geotechnical and geoenvironmental behaviour of high-density tailings

“…For hard rock thickened tailings of low plasticity, the evaporation rate follows classic soil drying (Simms et al 2007;Fisseha et al 2010;Daliri et al 2016), where evaporation decreases with time after deposition of fresh tailings. This decline may be accelerated by high salinity (or high concentrations of dissolved mass in the pore water) -as salinity decreases evaporation by multiple mechanisms of osmotic suction, high albedo (reflectivity to shortwave radiation), and formation of a salt crust Dunmola 2012).…”

“…This decline may be accelerated by high salinity (or high concentrations of dissolved mass in the pore water) -as salinity decreases evaporation by multiple mechanisms of osmotic suction, high albedo (reflectivity to shortwave radiation), and formation of a salt crust Dunmola 2012). While cracking does occur, the frequency and size of the cracks appear insufficient to substantially increase evaporation in low-plasticity hard rock tailings (Simms et al 2007;Fisseha et al 2010;Daliri et al 2016). In tailings with significant clay content, however, cracking appears to be a very important mechanism to maintain relatively high evaporation rates.…”

Cracking, salinity and evaporation in mesoscale experiments on three types of tailings

“…Other aspects of these tests are reported elsewhere (Daliri et al 2016;Innocent-Bernard et al 2014;Rozina et al 2015).…”

“…More details on these and similar types of tests are presented by Daliri et al (2016), Innocent-Bernard et al (2014 and Rozina et al (2015).…”

Sustainability and Tailings Management in the Mining Industry: Paste Technology

“…Hence, measuring CPB's performance is vital for a capable mine backfill design. In recent times, surface paste disposal (SPD) has been proposed in the mining industry as an alternative system to conventional mine tailings disposal methods for above ground storage [31,32]. Derived from the backfill technique being used for underground modern mines, it can be implemented with or without cement addition.…”