Thesis (M. Eng.)(Metallurgical)--University of Pretoria, 2005. / Includes summary. Includes bibliographical references. Available on the Internet via the World Wide Web.

Thesis (B.S.)--University of Missouri, School of Mines and Metallurgy, 1912. / The entire thesis text is included in file. Typescript. Illustrated by authors. Deane Dwight Harris received a Bachelor of Science degree in Metallurgical Engineering and Duane Montgomery Kline received a Bachelor of Science degree in Mining, both determined from "1874-1999 MSM-UMR Alumni Directory". Title from title screen of thesis/dissertation PDF file (viewed )

Mining has been one of the main industries in the course of the development of human civilization and economies of various nations. However, every industry has issues, and one of the problems the mining industry has faced is the management of waste, especially sulphide-bearing tailings, which are considered to be a global environmental problem. This issue puts pressure on the mining industry to seek alternative approaches for tailings management. Among the several different types of methods used, cemented paste backfilling is one of the technologies that offers good management practices for the disposal of tailings in underground mines worldwide. Cemented paste backfill (CPB) is a cementitious composite made from a mixture of mine tailings, water and binder. This technology offers several advantages, such as improving the production and safety conditions of underground mines. Among these advantages, CPB is a promising solution for the management of sulphidic tailings, which are considered to be reactive materials (i.e., not chemically stable in an atmospheric condition) and the main source of acid mine drainage, which constitutes a serious environmental challenge faced by mining companies worldwide. Such tailings, if they come into direct contact with atmospheric elements (mainly oxygen and water), face oxidation of their sulphidic minerals, thus causing the release of acidic drainage (i.e., acid mine drainage) and several types of heavy metals into surrounding water bodies and land. Therefore, the reactivity of sulphidic tailings with and without cement content can be considered as a key indicator of the environmental behavior and durability performance of CPB systems. For a better understanding of the reactivity, it is important to investigate the influencing factors. In this research, several influencing factors are experimentally studied by conducting oxygen consumption tests on different sulphidic CPB mixtures as well as their tailings under different operational and environmental conditions. These factors include time, curing temperature, initial sulphate content, curing stress, mechanical damage, binder type and content, and the addition of mineral admixtures. In addition, several microstructural techniques (e.g., x-ray diffraction and scanning electron microscopy) are applied in order to understand the changes in the CPB matrices and identify newly formed products. The results reveal that the reactivity of CPB is affected by several factors (e.g., curing time, initial sulphate content, ageing, curing and atmospheric temperature, binder type and content, vertical curing stress, filling strategy, hydration and drainage, etc.), either alone or in combination. These factors can affect reactivity either positively or negatively. It is observed that CPB reactivity decreases with increasing curing time, temperature (i.e., curing and atmospheric temperatures), curing stress, binder content, the addition of mineral admixtures, degree of saturation, and the binder hydration process, whereas reactivity increases with increases in sulphide minerals (e.g., pyrite), initial sulphate content, mechanical damage, and with decreased degrees of saturation and binder content. The effect of sulphate on the reactivity of CPB is based on the initial sulphate content as well as curing time and temperature. It is concluded that the reactivity of CPB systems is time- and temperature-dependent with respect to other factors. Also, binders play a significant role in lowering CPB reactivity due to their respective hydration processes.

M.Ing. (Civil Engineering) / The dissolved air flotation process can be used for different functions in the drinking waterand sewage treatment fields. The focus for this study was on thickening of activated sludge. At first literature was studied to identify all possible parameters. Then five plants were visited periodically and the physical layout and operating parameters were documented. With the examination of the data the different existing models were evaluated, and new relationships were investigated.

D.Tech. (Extraction Metallurgy) / Please refer to full text to view abstract

M.Tech (Metallurgy) / Nickel in South Africa is scarce. Other than as a by-product from platinum mining, its only source is the Uitkomst Complex, a satelite of the Bushveld Igneous Complex, located between Machadodorp and Barberton and mined by Nkomati Nickel. Pentlandite occurs as the main nickel-bearing mineral, disseminated within a sulfide matrix of pyrrhotite, pyrite and chalcopyrite. Accessories are of chromite and platinum in solid solution with the sulfides. The sulfides are hosted in mainly ultramafic rocks. The presence of talc is of particular nuisance. Head grade is in the decline, from earlier 0.7 to more recently 0.3% or even lower. Standard froth flotation yields a concentrate of 7 – 9% nickel at a recovery of up to 70%. A higher nickel recovery from such low – grade feed stock would be desirable. To achieve these two methods were investigated and reported in the following:  Non-oxidative leaching as an alternative to flotation, using strong hydrochloric and sulfuric acid and also aqueous ammonia solutions at various liquid-to-solid ratios. Only the degree of nickel dissolution over time at room temperature was studied and no attempt was made to recover the dissolved metal from solution.  Froth flotation after pre-treatment with microwaves at various power levels and over various periods of time of irradiation. It was surmised that a certain amount of inter-granular cracking could thus be achieved that would improve the flotation behavior in respect of grade and recovery. An extensive literature study, in particular, of the nature of microwaves, their interaction with matter and possible metallurgical benefits derived as a consequence of such interaction, forms part of the investigation and is reported in detail. A lot of theoretical and experimental work has been done in this respect, although the obtained results were not conclusive.

Smaltjärnen tailings repository located in Yxsjöberg, Sweden, attracts researchers with questions regarding characterization and potential re-mining. This thesis continuous geophysical characterization done by researchers from the Exploration Geophysics department at Luleå University of Technology but using new data from 2019. Geophysical methods used were self potential (SP), direct current resistivity (DCR), induced polarization (IP), and ground-penetrating radar (GPR). SP data were collected using a fixed base procedure and equipment from EMIT. Data were processed in MATLAB and presented in Oasis Montaj/ Geosoft software, yielding results difficult to interpret. Similar pattern was seen in previous investigations from 2016. However, some discrepancies were noticed, and more work is needed in order to validate these data. Therefore, data is presented without any interpretation. RES2DINV inversion software by Geotomo Software (now maintained by Aarhus GeoSoftware) was used for inversion of DCR data to produce four 2D resistivity sections, and the 3D resistivity model was made by Jingyu Gao with his software. DCR data were acquired by using Terrameter LS by ABEM and measuring using a roll-along procedure and dipole-dipole configuration. Results show consistency between vertical variations at profile crossings from different profiles. Three layers are indicated from results, interpreted to contain mine tailings and quaternary deposits, at some locations interpreted to be water-saturated, and bedrock. No IP effect is seen at Smaltjärnen. GPR data were processed in GPRSoft® PRO produced by Geoscanners to understand internal structures and water table, by using zero-offset surveying with 250 MHz antenna from Malå Geoscience and 300 MHz antenna from Geoscanners. Since the tailings of Smaltjärnen consists of very thin layers, the results are complex to interpret. Hyperbolas and layers, along with other more uncertain patterns, are seen in radargrams, and further research is needed to fully understand the images.

Doctor Scientiae / Acid Mine Drainage (AMD) is identified as one of the contributors to environmental hazard in the gold mining region of South Africa, as caused by the mining operational activities performed by mining industries in South Africa. This effect motivates the development of AMD prediction techniques application and geochemistry modelling using gold tailing dams located in West Rand area, Witwatersrand Basin as a case study. Control strategies are devised to assess, understand and measure the acidic potential generation of waste materials in ensuring the right method required to analyse risks caused by AMD to environment. The method encompasses mineralogical and geochemical analysis of 93 samples collected, AMD prediction, test modification and geochemical modelling. This method was appropriately applied to understand the basic mechanisms involved in controlling acid generation, assessing prediction procedure and selecting the right prediction tools. Study objectives are attained by performing a series of experimental lab tests on the samples collected from the two major tailing dams (Mogale and Gold One_1 tailings). Results derived from the lab experiments (XRD and SEM-EDS) show presence of mineral phases characterised with the surface feature of samples, and unknown substances of samples were identified. Geochemical characterisation was performed by XRF and ICP-MS to determine the major oxides elements and trace elements, respectively. Leco test generate total sulphur and total carbon. Multistatistical analysis is used to interpret the data derived from geochemical characterisation process to explicate the metal and trace elements distribution and occurrence. Initial samples were screened and categorised based on paste pH and EC using kinetic tests to determine acid-forming and neutralising minerals in samples and static tests to determine acid generation potential in samples. Net Acid Producing (NAPP) was mathematically calculated from Acid Neutralising Capacity (ANC), Maximum Potential Acidity (MPA) and total Sulphur. Results obtained from the Paste pH demonstrate that samples collected from 1 meter downward the holes to 10 meters, with a few meters samples in hole T003 at Gold One_1 are non-acidic while the remaining tailing samples are acidic. ANC/MPA ratio was applied to assess the risk of acid generation from mine waste materials. Graphical illustrations of the Acid Base Account (ABA) are plotted to demonstrate the net acidic generation potential trends of samples, which were classified into non-acid forming, potential acid forming and uncertain categories. Results integration between ANC, Single Addition Net Acid Generation (NAG) test and NAPP were used to classify acid generation potential of the samples. Leachate collected from leaching column test were analysed for pH, EC and chemical element by ICP-MS. The leaching column test used to analyse samples (T004) and (T001) collected from the two major tailings was set up for a 4-month experiment. Study findings present environmental assessment report on the two investigated gold tailing dams in Witwatersrand Basin area. Other findings are improved understanding of the application and limitations of various existing AMD prediction methods for assessment of gold mine waste and conceptual geochemical modelling developed to test appropriate methodology for AMD potential at a given gold mine site.

Liquefaction is a major challenge in geotechnical engineering in which soil strength and stiffness are compromised due to earthquake activity. Understanding and predicting the behaviour and liquefaction susceptibility of soils under cyclic loading is a critical issue in civil engineering, mining and protective engineering. Numerous earthquake-induced ground failure events (e.g., substantial ground deformation, reduced bearing capacity) or liquefaction in natural fine-grained soils or manmade fine-grained soils (i.e., fine tailings) produced by mining activities have been observed and reported in the literature. Tailings are manmade soils that remain following the extraction of metals and minerals from mined ore in a mine processing plant. Traditionally, such tailings are stored in surface tailings impoundments at the mine’s surface. However, geotechnical and environmental risks and consequences related to conventional tailings impoundments have attracted the attention of the engineering community to develop novel methods of tailings disposal and management to minimize geotechnical and environmental risks. Thus, engineers have introduced and implemented innovative tailings technologies—thickened tailings and paste tailings—as cost-effective means for tailings management in mining operations. As both thickened tailings and paste tailings have lower water content and higher solid content than tailings in conventional impoundments, these tailings may be more resistant to liquefaction. However, it should be noted that the seismic or cyclic behaviour of these thickened and paste tailings, with and without heavy rainfall effects, are not fully understood. There is little technical information or data about the behaviour and liquefaction of thickened and paste tailings under seismic or cyclic loading conditions. The objective of the present PhD research is to investigate the response of layered thickened and paste tailings deposits, with and without heavy rainfall effects, to cyclic loads by conducting shaking table tests. To simulate the field deposition of thickened and paste tailings, tailings were deposited in three thin layers in a flexible laminar shear box (FLSB) attached to the shaking table equipment. A sinusoidal seismic loading at a frequency of 1 Hz and peak horizontal acceleration of 0.13g was applied at the bottom of the layered tailings deposits. Acceleration, displacement and pore water pressure responses to the cyclic loading were monitored at the middle depth of each layer of the tailings deposits. Regarding the acceleration response of these thickened and paste tailings deposits (without the effect of heavy rainfall), there was no difference between the middle of the bottom and middle layers or at the base of the shaking table. However, the acceleration at the middle of the top layer differed from the acceleration at the base of the shaking table. Throughout shaking, the layered tailings deposits (with and without the effect of heavy rainfall) exhibited contraction and dilation responses. The excess pore water pressure ratios of the layered thickened tailings deposit that was not exposed to heavy rainfall prior to shaking were found to exceed 1.0 during shaking. However, for the layered paste tailings deposit that was not exposed to the effect of heavy rainfall prior to shaking, the excess pore water pressure ratios were found to be lower than 0.85 during shaking. This reveals that without the effect of heavy rainfall, the layered thickened tailings deposit was susceptible to liquefaction, whereas the layered paste tailings deposit was resistant to liquefaction during shaking. The excess pore water ratios of the layered thickened and the paste tailings deposits that were exposed to heavy rainfall prior to shaking were found to be lower than 0.8 during shaking. This reveals that with the effect of heavy rainfall, the layered thickened and paste tailings deposits were resistant to liquefaction during shaking. The results and findings of this PhD research thus provide valuable information for the implementation of tailings in earthquake-prone areas.

El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado. / In the mining industry, due to the extraction and processing of ore, a significant amount of tailings are produced which are discharged into deposits. In some cases, these are in contact with effluents and generate acid waters that pollute the environment and affect the health of the inhabitants. Additionally, these tailings within their composition contain valuable metals that can be reused through a process of mineral flotation. As a part of this research, a study based exclusively on laboratory tests was performed on the tailings deposit located in the Recuay–Peru district, where the presence of concentrations of Pb, Zn, and Ag at 48.36% was obtained, 23% and 250 g/TM. Thus, this study aims to take advantage of polymetallic tailings deposits that are in an abandonment state by extracting valuable ore through the flotation process based on their chemical composition and mineralogical characterization.