Growth and survival of native upland and wetland species in shallow capped thickened tailings: a meso-scale greenhouse study

Degenhardt, Dani; Dongen, Angeline Van; Schreiber, Stefan G.; Bekele, Asfaw

doi:10.1139/cjss-2022-0113

Cited by 1 publication

(2 citation statements)

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“…At SFR 1, the average solids content exceeds a superseded stringent regulatory directive once instituted by one jurisdiction requiring 50% capture of fines in deposits (AER directive 074) [38]. A value of >65% (w/w) solids content is a high enough unit weight to allow capping and reclamation cover operations [12,39,40]. The bottom-third portion of the deep deposit is beyond the plastic region and can be considered semisolid.…”

Section: Resultsmentioning

confidence: 99%

“…The focus of our studies is on creating geotechnically stable deposits. Stable deposits allow capping and reclamation cover work so that the deposits can ultimately become ecosystems, including vegetation, equivalent to their pre-disturbance landforms [12]. This portion of the project is limited to understanding the impact of a widely available tailings material, fine sand, on the consolidation of FFT-sand mixtures.…”

Section: Introductionmentioning

confidence: 99%

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Accelerating the Consolidation of Thickened Tailings Using Sand Co-Disposal

Demoz

2023

Minerals

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Only grams or kilograms of valuable resources are extracted for each tonne of ore processed, generating immense amounts of tailings. Returning tailings-containment dams to their equivalent pre-disturbance landscape state is many stakeholders’ acceptable management strategy. The depositing of thickened fluid fine tailings (FFT), which the industry has relied upon to develop geotechnically stable dry landscapes, has not materialised due to the low hydraulic conductivity of such placements. The addition of sand to thickened FFT is proposed to accelerate the consolidation of thickened FFT in a co-disposal scheme, and this study evaluates its impact. In the continuum of solid wastes from mining operations, sand is the next-larger-sized grade of solids after “fine” that is produced in high proportions. Blends of highly-plastic FFT and fine-grade sand tailings at varying sand-to-fine ratio (SFR) values were tested. Sand lowered the liquid limit but did not significantly affect the plastic limit of FFT. The changes in liquid and plastic limits for SFR ≥ 1 blends were under 5% of water content. The maximum unit weight for the co-disposal mixes was obtained at SFR 3. Despite increases in unit weights, hydraulic conductivity increased with increasing SFR, while the trend for compression rates was in the reverse order. Void ratio—effective pressure—hydraulic conductivity power law relationships at varying SFR were obtained from the consolidation measurements. The constitutive constants of these relationships were used to model settlement of 30 m deep pits over a 25-year period. For all the deposits studied, the dewatering converged to a maximum solids content characteristic of each SFR in the order 74, 85, 88, and 94% (w/w) for thickened FFT and SFRs 1, 2, and 3, respectively. The numerically calculated average solid contents of the deep-pit placements grew closer with increasing SFR becoming 59, 77, 82, and 86% (w/w), respectively. Balancing the consolidation-rate gains and the land footprint required for storage with SFR increase, the optimal composition for co-disposal for this material and similar tailings is SFR 1.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%