No description available.

The stress-strain and volume (or pore pressure) change characteristics of a Southern Arizona copper mine tailings material were investigated in the laboratory by conducting static loading triaxial compression tests. The tailings material is silty sand with highly angular grain shapes, rough grain surface texture and approximately 37% by weight passing No. 200 sieve. Isotropically consolidated drained (CID) and isotropically consolidated undrained (CIU) tests were performed on laboratory compacted samples. The test samples were loaded to relatively large axial strains (20-35%) to study the residual shear strength and the shear stress induced pore pressure change or volume change at steady state. Test sample densities and effective confining stresses were systematically varied in these tests. The definition of critical void ratio and "lower" critical void ratio were reviewed and their values for different effective confining stresses were obtained from the CID tests. Stress-strain and volume (or pore pressure) change curves and strength parameters obtained by using conventional and lubricated loading end platens were compared and discussed. Steady state lines and undrained brittleness indices were obtained from the CIU tests with strain-controlled and load-controlled loading methods. The liquefaction potential of the tailings material was then evaluated. These results were compared with others reported in the literature. The significance of the results was discussed with respect to tailings material behavior.

No description available.

Thesis (Ph. D.)--University of Adelaide, Dept. of Civil Engineering, 1992. / Includes bibliographical references.

Thesis (Ph.D.) - University of Queensland, 2006. / Includes bibliography.

A project report submitted to the Faculty of Engineering, University of the Witwatersrand, Johannesburg, in partial fulfillment of the requirements for the degree of Master of Science in Engineering. / The project report deals with the relationship between the undrained shear strength and the moisture content of Red Berea sand tailings. The tailings were obtained from the Red Berea sand dunes near Richards Bay, Kwa-Zulu Natal, South Africa. The geology of the area consists of Miocene deposits of red clayey sand, classified as Berea Formation. A method for determining stability of a tailings dam for Red Berea sand tailings, was investigated. The general method of using the degree of saturation of the tailings to specify the rate of rise, is not applicable to this type of tailings. It was found that a relationship exists between the undrained shear strength of the tailings, and the moisture content. The moisture content can easily be measured and the undrained shear strength can then be calculated. The calculated undrained shear strength can be used in a total stress analysis to determine a factor of safety against failure. This project report consists of a discussion of the literature, which was used as the basis for the assumptions made, as well as a description of the tests performed to prove the above-mentioned relationship. Test results are given, interpreted and used in an illustrative example of a stability analysis. / Andrew Chakane 2020

A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy. Johannesburg, 2016. / Gold mining of the Witwatersrand Basin reefs has been responsible for the rise of Johannesburg as an economic centre of South Africa. While mining provided a base for business and infrastructure development for the region, it has also generated social and environmental problems for the country. Tailings storage facilities (TSFs), a common sighting around Johannesburg and across the entire basin, have been built to contain the processed waste following extraction of gold from the pyrite containing quartzite ore. When the fine grained waste is exposed to atmospheric conditions, oxidation of remnant sulphides occurs resulting in acidic, metal rich and sulphate rich plumes that enter the environment through surface and groundwater systems. This thesis sought to better understand the release, transport, dispersal and fate of metals emanating from TSFs and their remnant footprints on the Witwatersrand. These metals included aluminium, copper, chromium, iron, manganese, nickel and uranium and are known to be toxic to humans depending on their concentration and speciation. Traditionally, analytical methods have been employed in studies focussing on the characterisation of some of these processes in the region. While these studies have generally conducted quantitative assessment of the extent of pollution, little comprehensive interrogation and fingerprinting of the processes that are influential in determining the potential risk posed by metals has been done. This has largely been due to the shortcomings of analytical methods to determine these. To this end, this research has employed geochemical modelling to complement the traditional analytical methods. The approach to study the release of metals from TSFs involved assessment of the partitioning of metals within tailings and their potential release using batch and sequential extraction methods. Processes of metal release within the tailings were simulated through geochemical modelling (using the PHREEQC and Geochemist’s Workbench codes). The simulations were based on the percolation of rainwater through these layers and the changes in its chemistry along the path. The potential seepage of this plume along the path was then correlated to observed efflorescent mineral crusts that are temporary sinks for metals and are a common feature in the vicinity of the tailings and water bodies such as ponds and streams. The potential impact of the mineral crusts on the water chemistry of receiving water systems following their dissolution was assessed using forward geochemical modelling. The transport of the metals in groundwater was also studied. This involved simulations of the transition in chemistry of a plume from a TSF along an aquifer of known composition. This was based on a 1-D reactive transport model constructed using information from sequential extraction work on the aquifer rock (to identify the key minerals to consider) and site data (mainly flow rates) from previous studies. The processes occurring in the removal of metals from acid mine drainage (AMD) through a permanent sink in the form of a pump-and-treat plant in the Central Goldfield of the basin were simulated using PHREEQC. The findings from the research showed that two different plumes were produced from an abandoned TSF as a result of rainwater percolation, notably a plume produced from the dissolution of secondary salts formed in the oxidised layer and a sulphuric acid rich plume in the unoxidised layer. These differences were apparent in the geochemical composition of the mineral crusts collected on the walls of tailings dumps and from a pond into which the plumes were draining. On dissolution, mineral crusts were found to produce acidic solutions with crusts containing predominantly Fe producing pH values below 3. The simulated dissolution of various types of mineral crusts gave insight into the impact of minerals present in the smallest amount. This showed that the bulk mineralogy as determined by analytical techniques such as PXRD and remote sensing could not be used with confidence to deduce the impact of the mineral crusts on receiving water bodies. The characteristics of surface plumes released from tailings TSF were compared to other water systems in the area around Soweto, with complementary interpretation conducted using chemometric methods. From principal component analysis (PCA), surface water systems were found to form distinct groups largely influenced by mineral solubility, alkalinity and dissolved oxygen content. The 1-D reactive transport simulations involved acidic, metal and sulphate rich water ingressing the aquifer (below the TSF). Several scenarios were modelled including simulations with different dolomite contents; allowing for surface complexation and the presence of cation exchange surfaces. At a point 500 m from the water ingress in the dolomite rich aquifer, Fe and Mn were largely precipitated out (as confirmed by sequential extraction results on the aquifer rock) while the sulphate concentration was reduced by almost half. On the other hand, Ca concentrations were conservative largely because of continuous dissolution of dolomite and precipitation of gypsum along the flow path. The simulations of the high density sludge treatment plant involved forward modelling of the treatment process with the sludge responsible for the removal of trace metals from the incoming acid mine drainage. The model can be of use for cost and process optimisation at the facility. This research has had notable outputs in the form of publications; models on metal release, transport and attenuation; and models on pump-and-treat processes. These will form an important repository of information and for benchmarking any further studies related to AMD. / MT2016

Includes bibliographical references / xii, [291] leaves : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Civil Engineering, 1992

M.Sc. / The Merriespruit Tailings dam disaster killed seventeen (17) people and covered a part of Virginia with approximately 2.5 million cubic metres of tailings, causing such an emotional uproar that all resources were focused on repairing the dam and addressing some of the social issues. Little attention was given to the environment. The identified need in this study was therefore to investigate the consequences of the disaster on the environment, a need which derives from the uniqueness of this particular disaster and its consequences. The Department of Minerals and Energy require the submission of an Environmental Management Program Report (EMPR) on all prospecting and mining operations. It is clear that, in the compilation of such an EMPR, Harmony Gold Mine neglected to establish a Management Plan to regulate the physical impact of the disaster on the environment, mainly because no attention was given to disasters in the Aide-Memoir. A Management Plan was established by adapting existing formats of management plans to the uniqueness of this disaster. By following the procedure stipulated in the Management Plan it can be ensured that Environmental Management requirements will be effectively integrated into either the project management actions and contracts or operational systems and processes for the following issues: • Water management • Storm water control • Waste management • Dust • Aesthetics and socio-economic implications • Rehabilitation of the area. The investigation showed that the disaster exerted a definite negative influence on the environment, which can be managed by taking preventative measures stipulated in the Management Plan. However, one of the main issues identified in this study is that storm water management has been problematic for a period of time. It is therefore noted that some attention should be given to establishing a wetland system to contain the storm water runoff. Although this study does not focus on the socio-economic impacts in detail, it is recommended that these impacts are considered as it is evidently problematic. The primary aim of this study was to compile an EMP in order to manage, and possibly mitigate, the physical impact of the disaster on the immediate environment, an aim which clearly was accomplished. Harmony Gold Mine can benefit from the compilation of this EMT, as management goals were set and feasible means of achieving them were specified.

[Truncated abstract] As mineral deposits continue to be mined, the non economic gangue materials such as sulphides (e.g. pyrite) that are extracted as part of the ore body or overburden are deposited within the waste rock and/or milled tailings. As a result of natural weathering processes, these reactive materials represent a potential hazard to surrounding environments. A major consequence, resulting from mine-waste impoundments containing sulphidic materials, relates to the offsite movement of low pH leachates containing elevated concentrations of metal ions posing a contamination threat. The processes and mechanisms acting in the formation of acid mine drainage (AMD) are highly variable and, to a high extent, controlled by climatic conditions as the main driver of water flow and wetness of the system which in turn determines the availability of oxygen as well as water for pyrite weathering. In particular, this thesis is based on the hypothesis that in semiarid and arid climates the acid production may be water … The experiments were repeated at different water contents ranging from 0.24 to 0.33 cm3 cm-3. Breakthrough curves (BTC) of Li+, K+, Ca2+, Mg2+, Na+ and pH were measured and described with models of different complexities. This included the use of a simple linear and non-linear isotherms for Li+ alone, a binary Li+ - K+ ion exchange, and a complete multicomponent chemical equilibrium description of ion transport. The latter, by including dissolution of primary minerals which released base cations such as Mg2+, Ca2+ and K+ explained some of the elution patterns of base cations for which the Li+ - K+ exchange was the dominant process. Furthermore, under unsaturated water flow conditions, retardation of Li+ increased with decreasing water content. Thus solute mobility in mafic rock tailings appears to decrease under strongly unsaturated water flow conditions.