Prediction of acid rock drainage in waste rock piles part 2: Water flow patterns and leaching process

Blending of potentially acid generating (PAG) waste rock with non-PAG waste rock to create a rock mixture which performs as non-PAG is a possible approach to permanent prevention of acid rock drainage (ARD) for PAG waste rock. In 2012, a field weathering study using 300 kg samples was implemented at Teck Coal's Quintette Project located in northeastern British Columbia, Canada to test the prevention of acid generation in the PAG waste rock by dissolved carbonate leached from overlying non-PAG waste rock and direct neutralization of acidic water from PAG waste rock by contact with non-PAG waste rock.After eight years of monitoring the experiments, the layered non-PAG on PAG barrels provided proof-of-concept that as the thickness of the PAG layer increases relative to the thickness of the non-PAG layers, acidic waters are more likely to be produced. The PAG on non-PAG layering has resulted in non-acidic water and no indications of metal leaching despite accelerated oxidation in the PAG layer shown by sulphate loadings. The study has demonstrated that the scale of heterogeneity of PAG and non-PAG materials is a critical consideration for providing certainty that rock blends designed to be non-PAG will perform as non-PAG in perpetuity. This is contrary to the standard paradigm in which an excess of acid-consuming minerals is often considered sufficient alone to ensure ARD is not produced.

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Performance of engineered test covers on acid-generating waste rock at Whistle mine, Ontario

Canadian Geotechnical Journal ◽

10.1139/t05-088 ◽

2006 ◽

Vol 43 (1) ◽

pp. 1-18 ◽

Cited By ~ 24

Author(s):

Celestina Adu-Wusu ◽

Ernest K Yanful

Keyword(s):

Acid Rock Drainage ◽

Geochemical Modeling ◽

Thick Layer ◽

Waste Rock ◽

Test Plot ◽

Layer System ◽

Acid Rock ◽

Geosynthetic Clay Liner ◽

Clay Liner ◽

Sandy Silt

This paper presents the design and 3 year field performance results of three engineered test soil covers for the mitigation of acid rock drainage (ARD) at Whistle mine near Capreol, Ontario. Each test cover was a two-layer system consisting of a 0.90 m noncompacted pit-run gravelly sand overlying a barrier layer. The three barrier layers studied were a 0.46 m thick mixture of sand (92%) and bentonite (8%) (SB), a 0.60 m thick layer of sandy silt with about 5% clay (SS), and a 0.008 m thick geosynthetic clay liner (GCL). Each cover was installed on 6.10 m thick acid-generating waste rock and was instrumented and monitored along with a control test plot that consisted of 6.10 m of waste rock. The ultimate objective of the study was to select a suitable cover for full-scale decommissioning of acid-generating waste rock backfilled into the Whistle pit. Results from 3 years of monitoring showed that the GCL was the most effective barrier in reducing percolation into the underlying waste rock. Percolation through the GCL barrier was 7% over the 3 year period compared with 20% and 59.6% through the sandbentonite and sandy silt barriers, respectively, and 56.4% through the control plot. The overall quality of percolate water from the covered waste rock was much better than that of percolate water from the uncovered waste rock. Aqueous geochemical modeling suggested that percolate water draining the oxidized waste rock was controlled by hydroxides, oxide, and sulphate phases of Al, Ca, Mg, and Fe3+.Key words: waste rock, acid rock drainage (ARD), capillary barrier, geosynthetic clay liner, amended soil systems, percolation, MINTEQ.

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Planning and Construction of a Waste Rock Dump through Waste Sorting to Prevent a Potential Acid Rock Drainage Problem

Journal American Society of Mining and Reclamation ◽

10.21000/jasmr92010233 ◽

1992 ◽

Vol 1992 (1) ◽

pp. 233-240

Author(s):

L. R. Rohde

Keyword(s):

Acid Rock Drainage ◽

Waste Rock ◽

Acid Rock ◽

Waste Rock Dump ◽

Drainage Problem ◽

Potential Acid ◽

Planning And Construction

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Mechanical response of highly gap-graded mixtures of waste rock and tailings. Part I: Monotonic shear response

Canadian Geotechnical Journal ◽

10.1139/t09-126 ◽

2010 ◽

Vol 47 (5) ◽

pp. 552-565 ◽

Cited By ~ 14

Author(s):

Ali Khalili ◽

Dharma Wijewickreme ◽

G. Ward Wilson

Keyword(s):

Management Practices ◽

Mechanical Response ◽

Acid Rock Drainage ◽

Mine Waste ◽

Shear Loading ◽

Waste Rock ◽

Traditional Methods ◽

Acid Rock ◽

Shear Response ◽

Rock Particle

The idea of mixing mine tailings and waste rock to form “paste rock” prior to disposal is now receiving significant attention from the point of view of sustainable mine waste management practices. This approach has been viewed as a favourable alternative to traditional methods of mine waste disposal because paste rock has the potential to overcome deficiencies (e.g., acid rock drainage and liquefaction-induced failures) associated with traditional methods. To advance the current limited knowledge, a laboratory research program was undertaken to study the mechanical response of paste rock. Testing was undertaken on paste rock specimens prepared so that the tailings would “just fill” the void spaces within the waste rock particle skeleton. The findings suggest that the material is unlikely to experience flow deformation under monotonic shear loading conditions, at least up to the tested initial effective confining stress conditions of 400 kPa. The monotonic shear response of paste rock was found to be similar to that of rock-only material; this finding is in agreement with previous observations from one-dimensional consolidation testing where it had been shown that the rock particle skeleton would carry almost 90% of the externally applied stress on a given paste rock mass.

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