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Permanent link (DOI): https://doi.org/10.7939/R3V30N

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HEAT TRANSFER IN WASTE-ROCK PILES CONSTRUCTED IN A CONTINUOUS PERMAFROST REGION Open Access

Descriptions

Other title
Subject/Keyword
Natural air convection
Acid Rock Drainage (ARD)
Permafrost
Waste rock piles
Heat transfer
Type of item
Thesis
Degree grantor
University of Alberta
Author or creator
Pham, Hoang Nam
Supervisor and department
Sego, Dave (Civil and Environmental Engineering)
Wilson, Ward (Civil and Environmental Engineering)
Examining committee member and department
Rajaratnam, N (Civil and Environmental Engineering)
Flynn, Morris (Mechanical Engineering)
Ulrich, Ania (Civil and Environmental Engineering)
Côté, Jean (Civil Engineering, Université Laval)
Department
Department of Civil and Environmental Engineering
Specialization
Geotechnical Engineering
Date accepted
2013-01-10T09:37:31Z
Graduation date
2013-06
Degree
Doctor of Philosophy
Degree level
Doctoral
Abstract
This study is a part of a field experiment constructed at the Diavik Diamond Mine in northern Canada to investigate water flow, geochemical reactions, thermal and gas transport within unsaturated piles of mine waste rock in a continuous permafrost permafrost. Diavik waste rock is categorized by its sulfur content: Type I rock, Type II rock and Type III rock . Three experiment waste-rock piles of 15 m high were constructed to achieve the project objectives. Two uncovered test piles are referred to as Type I test pile (Type I rock) and Type III test pile (Type III rock). The third test pile is covered test pile in which the Type III rock is covered by a layer of 1.5 m till and 3 m Type I rock. Three drill holes of 40 m depth in a 80 m high pile were also instrumented to reexamine the results of the test piles. This thesis focuses on the thermal aspects of the project. Thermal measurements in the uncovered piles implied the importance of wind on heat transport. Temperatures within the piles were found to decrease with time and permafrost aggradation near the base and in bedrock foundation. At the covered pile, temperatures at and below the till cover were frozen. There was no significant impact of wind on temperatures below the cover and heat influx across the cover was small. Bedrock foundation temperature of the covered pile showed a small cooling trend and less fluctuation compared to bedrock foundation of the uncovered piles. Linear stability analysis for the onset of natural air convection in waste-rock piles with physical properties based on Diavik waste rock was also performed. The results indicate that oxidation can create sufficient temperature gradients (or buoyancy forces) to trigger natural air convection. Ground temperatures of three 40 m drill hole in the 80 m high full-scale pile showed that conduction was dominated and the pile was cooling. According to numerical simulations, using air convection cover (ACC) the 80 m high pile will be frozen for the next 100 years under a proposed climate warming for the site. Furthermore, numerical simulations also showed that ACC can maintain frozen condition within waste-rock piles even though there was a heat release due to sulfide oxidation. This heat release may create natural air convection within waste-rock piles which aids in its removal.
Language
English
DOI
doi:10.7939/R3V30N
Rights
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
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