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The Ruttan Cu-Zn mine produced approximately 30 million tons of fine-grained tailings over 30 years. Since the closure of the mine in 2002, the tailings have been systematically dewatered through trenches which drain into Ruttan Lake and into the open pit and underground mine workings. This study evaluated the evolution of the tailings of Cell 3, which was underwater in 2002, and Cell 2, which was already dry and oxidized. Dewatering the submerged tailings in Cell 3 resulted in measureable changes in acidification in pore and shallow groundwater from rapid oxidation of very fine grained sulphides. Depth profiles of the concentration of metals in dissolved and solid fractions, when compared to other studies, suggest that the tailings in Cell 2 and Cell 3 are in an early stage of oxidation and that these tailings will produce low pH, metal laden water for years.

The behavior of U in near surface sedimentary environments has changed throughout geologic time. There is a marked shift in U (IV) mineral stability and deposit style at approximately 2200 Ma due to changes in the concentration of O in the atmosphere. For example, prior to 2200 Ma, fluvial U deposits could form and U(IV) were stable in surface and near-surface environments. In modern, anthropogenic sedimentary systems such as U tailings, U (IV) minerals are not stable and readily oxidize to U (VI) minerals. In addition, U is much more mobile in modern sediments relative sediments that were deposited prior to 2200 Ma.

The Ruttan Cu-Zn mine produced approximately 30 million tons of fine-grained tailings over 30 years. Since the closure of the mine in 2002, the tailings have been systematically dewatered through trenches which drain into Ruttan Lake and into the open pit and underground mine workings. This study evaluated the evolution of the tailings of Cell 3, which was underwater in 2002, and Cell 2, which was already dry and oxidized. Dewatering the submerged tailings in Cell 3 resulted in measureable changes in acidification in pore and shallow groundwater from rapid oxidation of very fine grained sulphides. Depth profiles of the concentration of metals in dissolved and solid fractions, when compared to other studies, suggest that the tailings in Cell 2 and Cell 3 are in an early stage of oxidation and that these tailings will produce low pH, metal laden water for years.

The behavior of U in near surface sedimentary environments has changed throughout geologic time. There is a marked shift in U (IV) mineral stability and deposit style at approximately 2200 Ma due to changes in the concentration of O in the atmosphere. For example, prior to 2200 Ma, fluvial U deposits could form and U(IV) were stable in surface and near-surface environments. In modern, anthropogenic sedimentary systems such as U tailings, U (IV) minerals are not stable and readily oxidize to U (VI) minerals. In addition, U is much more mobile in modern sediments relative sediments that were deposited prior to 2200 Ma.

This master thesis has been conducted through cooperation between Elforsk, Uppsala University and Tsinghua University in Beijing. Ashele Tailings Dam, located in Haba Town, Xianjing Province, China, is designed and used for high sulphur tailings. Because of a new mineral separation technique, the dam is now also being filled with low sulphur tailings. Since the dam was not originally designed for the new tailings materials, the seepage and stress-strain analyses of the dam need to be re-evaluated and refined. The Ashele Ltd. is also planning on building a new dam to meet its growing need for tailings deposit capacity. This dam will be used for the new low sulphur tailings and a thorough analysis of the dam will have to be performed.The purpose of this thesis is to re-evaluate the analyses of the seepage and stress-strain in the old dam and to perform the same type of analyses on the newdam. Numerical analyses of the seepage, solute transport and strain-stress in the dam are performed, using the physical and mechanical properties of the tailings materials. It is shown, that the construction of the new tailings dam, will have a good effect on the seepage and therefore also solute transport. The results also show that theseepage, solute transport, stress and deformation are depending on the amount ofwater in the tailings pond and that a lower water level has a positive effect on all thestudied variables.

Thesis (Ph.D. (Civil and Biosystems Engineering)) -- University of Pretoria, 2009. / Summary in English. Includes bibliographical references.

Thesis (Ph. D.)--Montana State University--Bozeman, 2004. / Typescript. Chairperson, Graduate Committee: Alfred B. Cunningham. Includes bibliographical references (leaves 188-201).

Thesis (Ph. D.)(Civil Eng.)--University of Pretoria, 2004. / Summaries in English and Afrikaans. Includes bibliographical references.

Thesis (M.S.)--Montana State University--Bozeman, 2005. / Typescript. Chairperson, Graduate Committee: Alfred Cunningham. Includes bibliographical references (leaves 132-143).