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An application of risk based design in open pit mine planningBrits, Leilani 26 May 2014 (has links)
M.Ing. (Engineering Management) / The design of the optimum open pit slope angle is one of the major challenges during open pit mine planning, as it implies attaining the ideal balance between utilizing the maximum slope angle whilst achieving acceptable stability and safety standards as indicated by the mine. The aim of open pit mines should thus be to seek the steepest possible slope angle without compromising the safety of the personnel, equipment or ore reserves, utilizing both stability analyses as well as risk assessments. The typical open pit mine plan aims to achieve an acceptable balance between operational risks and geotechnical design considerations by analysing factors such as the slope stability design, the rock mass properties and existing structural geological conditions. These factors are used as inputs towards an optimum slope angle design which will be used in the final pit design and aims to provide maximum economic viability to the mine. The risk analysis methodology aims to improve traditional slope design methods and is used to evaluate risks and failure consequences in terms of economic impacts. The economic impact analysis is a useful method in comparing the performance of various mine plans and slope designs. The risk analysis methodology thus provides a valuable indication of optimum slope design configurations and as such can be a great asset to the mine design process. This research paper aims to identify the key risks used as input to an open-pit mine plan in a feasibility stage and to define an approach to minimize these risks in order to achieve maximum economic benefit. The effectiveness of this approach will be evaluated by means of a case study which will attempt to achieve an optimum balance between value and risk, and to compare the magnitude of the economic impact of an individual risk with the probability of occurrence of said risk. The case study will utilise a risk map in order to define years with higher economic impacts as well as defining critical pit areas causing these risks, so as to identify areas requiring further investigation which will assist the mine in evaluating mitigation strategies in order to reduce overall risk.
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ASSESSMENT OF POTENTIAL IMPACTS TO SUBSURFACE BODIES OF WATER DUE TO UNDERGROUND COAL MININGBode-Jimenez, Gabriel 01 January 2017 (has links)
Underground coal mining operations induce ground movements, which may impact overlying hydrogeologic systems. Potential impacts mainly include changes in the hydraulic conductivity of overlying strata, decreasing of the hydraulic head and changes in water flow. The present research quantifies potential hydrogeologic impacts caused by underground mining through modeling of pre- and post-mining hydrogeologic systems.
Three-dimensional conceptual hydrogeologic models were constructed with the Processing Modflow for Windows software package (PMWiN). The models are based on an actual case study, but were simplified in terms of geometry and material properties. Water flow was simulated under changing hydrogeologic properties. A number of scenarios were investigated including models with horizontal or inclined topography, featuring an aquifer overlying two longwall panels. The hydrogeologic properties of the models were estimated based on empirical relationships between the post-mining hydraulic conductivity and strain in the overburden. The strain regime in the overburden was estimated using the Surface Deformation Prediction System (SDPS) package, which allows calculation of surface deformations due to underground coal mining.
The research focuses on changes in hydraulic heads; results indicate that hydraulic heads may decrease over undermined areas and may rebound as mining ceases. Water infiltration may occur from higher located overburden formations to lower formations due to mining induced changes in hydrogeologic properties.
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FUNDAMENTAL IMPROVEMENT IN THE TRIBOCHARGING SEPARATION PROCESS FOR UPGRADING COALChen, Jinxiang 01 January 2017 (has links)
Triboelectrostatic separation is a physical separation technique that is based on surface electronic property differences among minerals to achieve a separation. Minerals have different surface conductivities and electron affinities. They are charged differently in quantity and/or polarity after a tribocharging process. Particles with different surface charges move discretely under external electric field produce a separation. Electrostatic separation is a dry mineral processing method that does not require any water or chemical reagents. It can greatly simplify the processing circuit and reduce operating cost. Additionally, problems caused by water in conventional wet mineral processing such as water freezing, dewatering, water pollution and water treatment are eliminated. Electrostatic separation has great potential as a fine particle separator (i.e. < 1mm) in industrial minerals processing application, especially in arid areas where water supply is limited.
In the current study, particle tribocharging kinetics was evaluated using a model system comprised of copper, pure coal, silica and ceramic. The results of the tribocharging process were recorded and analyzed using an oscilloscope and a signal processing technique. Charge exchange, charge separation and charge relaxation corresponding to tribocharging processes were studied using the generated pulsing signals. The signals provided a method to quantify the charge penetration into the conductor bulk during tribocharging. A new method to measure the particle surface charge using the pulsing was proposed and assessed, which was extremely useful for subtle surface charge measurements which effectively eliminated environmental noise. The interactive forces at the contacting interface, relative displacement, material electronic properties and ambient relative humidity were found to impact particle surface charge. The silica surface sites are 69 times more chargeable than the coal surface, which provides a fundamental explanation for upgrading that is achievable for silica-rich coal using triboelectrostatic separation. The influences of operating and environmental parameters were quantified and compared using an environment controlled chamber. Energy consumption at the interface was found to be positively correlated with the particle charge. Relative humidity has dual effects on the particle tribocharging, excessively low or high humidity levels do not favor particle tribocharging. Finally, a semi-empirical mathematical model of particle tribocharging was developed from the basic tribocharging compression model utilizing the parametric experiment study results. The model provides a more accurate method to predict particle surface charge under exact tribocharging conditions.
A novel rotary triboelectrostatic separator (RTS) using the tribocharging mechanism was tested for upgrading fine coal. The particle size influencing the RTS tribocharging and separation process is investigated. A practical method to quantify the particle charging distribution was developed based on the direct particle charge measurement and a Gaussian distribution assumption. The smaller particles were found to have a higher average surface charge and wider surface charge distribution, which provided an opportunity to separate the high grade and the low grade coal particles. However, particles that are too small have weak particle-charger tribocharging effect that reduces particle tribocharging efficiency. The particle separation process was analyzed considering the exact experimental hydrodynamic separating conditions. Smaller particles were found to be more sensitive to the airflow that used to transport the particles as a result of the effect on residence time in the separation chamber. A method combining mathematical and statistical analysis was proposed to theoretically predict RTS separation efficiency based on the particle charging conditions and particle separation conditions. The particle horizontal displacement probability distribution was ultimately derived from this method. The model predictions indicate that a wider horizontal displacement distribution provides improved separation efficiency for the RTS unit. The theoretical analysis indicates that a particle size range between 0.105 and 0.21 mm has widest horizontal displacement distribution and thus represents an optimum particle size range which is in agreement with experimental results.
The influences of the RTS operating parameters on separation performance achieved on a pure coal-silica mixture were investigated using a parametric study. The optimum operating conditions were identified. Using the optimum conditions, a five-stage separation process was conducted using the RTS unit to obtain the necessary data for the development of an ideal performance curve. Two stages of RTS separation were found to generate good quality clean coal with acceptable recovery. Particle tribocharging tests were performed using pure coal, pure silica and the coal-silica mixture as model feed materials. The test result found that mixing the pure coal with the sand reduced the particle charge distribution of the coal while increasing the charge distribution of the pure silica particle. The finding explains the inability to produce clean coal products containing ultra-low ash contents. However, the rejection of silica to the tailings stream is very high.
The RTS upgrading of low-ash coal sample was tried using experiment design method, which revealed that feed rate was the most significant while the applied charger voltage and the injection air rate were the least significant in regards to product quality. Feed mass flow rate and the co-flow air rate have a significant interactive effect. Considering the theoretical findings, the impact of high feed rates is due to the negative effect on particle tribocharging efficiency resulting from an increase in the particle-particle surface charge relaxation. Under the optimum test conditions, an ultraclean coal was produced with an ash content of 3.85±0.08% with a combustible recovery of 62.97±1.11% using the RTS unit.
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A Life Cycle Assessment of a Uranium Mine in NamibiaLambert, Janine 29 June 2016 (has links)
Uranium mining and nuclear power is a controversial topic as of late, especially in light of the recent Fukushima event. Although the actual use of nuclear fuel has minimal environmental impact, its issues come at the very beginning and end of the fuel’s life cycle in both the mining and fuel disposal process. This paper focuses on a life cycle analysis (LCA) of uranium mine in the desert nation of Namibia in Southern Africa. The goal of this LCA is to evaluate the environmental effects of uranium mining. The LCA focuses on water and energy embodiment such that they can then be compared to other mines. The functional unit of the analysis is 1kg of yellowcake (uranium oxide). The processes considered include mining and milling at Langer Heinrich Uranium (LHU). The impact categories evaluated include the categories in ReCiPe assessment method with a focus of water depletion, and cumulative energy demand.
It was found that the major environmental impacts are marine ecotoxicity, human toxicity, freshwater eutrophication, and freshwater ecotoxicity. These mainly came from electricity consumption in the mining and milling process, especially electricity generated from hard coal. Milling tailings was also a contributor, especially for marine ecotoxicity and human toxicity. The other electricity generation types, including nuclear, hydro, natural gas, and diesel contribute to marine exotoxicity and human toxicity as well. Hydro-electricity, tailings form milling, sodium carbonate, and nuclear electricity also cause freshwater eutrophication at the LHU mine.
The major contributor of the water depletion was hard coal generated electricity consumption as well. Tailings also led to a level of water depletion that was significant but much smaller than that of the coal-based electricity.
In terms of energy, weighting portrayed the main energy used to be nuclear power, in terms of MJ equivalents. Nuclear power was then followed by fossil fuels and finally hydropower. Most of the energy used was for the uranium mining process rather than the milling process.
As expected, the direct water, and energy values, 0.5459 m3 and 97.34 kWh per kg of yellowcake, were much lower than the LCA embodiment values of 282.67 m3 and 76,479 kWh per kg of yellowcake. When compared to other mines, the water use at LHU was found to be much lower while the energy use was found to be much higher.
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Integrated dynamic simulation of large thermal systemsArndt, D C 05 July 2006 (has links)
Studies concluded that more that 10% of all energy consumed in the world is expended by building air-conditioning systems. Energy efficiency in building and HVAC (Heating, Ventilating and Air-conditioning) design is therefore exceptionally important. A cost¬-effective way to improve the energy efficiency of a HV AC system, without compromising indoor comfort, is by implementing better control. System energy cost savings of up to 50% can be realised by optimising the system operating control strategies with direct payback periods of less than a year. However, when changing the operating strategy of a system it is often difficult to predict the resulting changes in system energy consumption and indoor comfort. To achieve these predictions, a dynamic simulation tool, which can efficiently and accurately simulate the building with the HV AC and control system in an integrated fashion, is required. Extensions to the integrated tool QUICKcontrol is therefore proposed to suite the needs of the energy service contractor. QUICKcontrol still has many shortcomings in the availability of component models for certain equipment commonly used in building systems today. New dynamic component models were therefore derived in this study. The accuracy and applicability of integrated building and natural ventilation modelling is illustrated in animal housing facilities. The predicted results obtained during this study were satisfactory to use these models with confidence in this type of building applications. The applicability of building, HV AC system and control simulations was illustrated in conference facilities. The results obtained show the value of integrated building and system simulation in the evaluation of energy cost saving inventions in commercial buildings. The mining and industrial sectors in South Africa consume about 40% of ESKOM's total electrical energy production. Mines alone use nearly 20% of the electricity provided by ESKOM. Ventilation and cooling (VC) systems are responsible for approximately 25% or R750 million of this energy. It will therefore be beneficial if the mines can be more energy clever in order to reduce their VC operating costs. The use of an extended integrated building and system simulation tool was therefore realised to investigate the potential for energy cost savings in mine VC applications. To extend QUICKcontrol for the simulation of other large thermal systems found in mining and industrial applications, new component models and simulations procedures were developed. Two case studies were performed with the extended tool to illustrate its applicability in thermal systems other than building systems. The potential for Demand Side Management (DSM) on a surface cooling plant and an underground clear water-pumping system was investigated. Satisfactory results were obtained during the two investigations to utilise this extended tool with confidence in practice. With more extensions to the tool it should be possible to investigate the potential for energy cost saving on any other thermal industrial applications. / Thesis (PhD (Mechanical Engineering))--University of Pretoria, 2007. / Mechanical and Aeronautical Engineering / unrestricted
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Determining the physical and economic impact of environmental design criteria for ultra-deep minesWebber, R C W 24 July 2006 (has links)
Please read the abstract in the section 00front of this document / Dissertation (M Eng (Mining Engineering))--University of Pretoria, 2007. / Mining Engineering / unrestricted
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Developing a concept that can be used to quantify the motion of flyrock, with the intention of eventually producing a measuring tool for future flyrock research.Van der Walt, Jennifer January 2019 (has links)
Flyrock remains a significant risk to the health and safety of the mine’s employees and infrastructure as well as the safety of the neighbouring communities and their property. Losses and damages can result in significant financial and reputation consequences. The lack of fundamental research in recent years and quantifiable data relating to the relationship between blast design parameters and the risk of flyrock motivated this project. A number of authors concluded that major gaps in knowledge relative to flyrock caused by its random nature still remain a weakness in the field.
Recent papers published (since 2010) proposed a wide range of potential approaches and techniques to predict or investigate flyrock. However, the majority of these papers concluded that the proposed results were site-specific and could not be applied to other environments.
The focus of this project was to develop a concept that is able to quantify the flight path of the flyrock resulting from a blast. The motivation behind the development of this concept was to enable future researchers to quantify the impact of the different blast design parameters on the measured flyrock.
Various technologies were considered and investigated during this project. After a comparative analysis of these technologies, it was decided to use photogrammetry as the foundation of the proposed concept tool. The proposed concept consists of three main phases, namely (1) data acquisition, (2) image processing and data analysis and (3) data interpretation.
To date, progress has been achieved with phase one and phase two. In phase one, all objectives have been met. However, there are still areas which need refinement, specifically regarding the placement of the cameras in the field. In phase two, success was achieved with the proof of concept exercise in a controlled environment using a clay pigeon as the projectile. The process of calibrating the lenses has been established, however, further optimization is possible. Point-cloud data was successfully generated in the concept test, but converting the image data from subsequent quarry test blasts proved more challenging and is still a work in progress. Once phase two has been satisfactorily resolved, attention will focus on phase three.
Results to date have given a positive indication that the concept is viable and that additional work will prove the technology functional. Ultimately, it is envisioned that this tool can be used for one of three purposes, namely:
• Mines can generate a database with accurate historical flyrock of their blasting operations.
• Research teams can implement this tool to conduct quantitative research and investigations into flyrock and the impact of different blast design parameters on the risk of flyrock.
• Point-cloud data combined with ballistics calculations can be used to visualise blasts and flyrock in Virtual Reality for training and education. / Dissertation (MEng)--University of Pretoria, 2019. / AEL Mining Services Chair in Innovative Rock Breaking / Mining Engineering / MEng / Unrestricted
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Bio Inspired Evolutionary Fuzzy System for Data ClassificationAbdulgader, Musbah M. January 2019 (has links)
No description available.
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A Combined Field, Laboratory, and Numerical Study of Cutter Roof Failure inCarroll Hollow Mine, Carroll County, OhioBecker, James B. 18 June 2013 (has links)
No description available.
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Post-liquefaction Residual Strength Assessment of the Las Palmas, Chile Tailings FailureGebhart, Tristan Reyes 01 September 2016 (has links) (PDF)
Assessment of post-liquefaction residual strength is needed for the development of empirically-based, predictive correlations for earthquake engineering design. Previous practice commonly assigned negligible strengths to liquefied materials for engineering analysis, producing overly-conservative designs. Increasingly available case history data, and improved analytical tools have allowed for more accurate and less overly-conservative estimation of soil residual strength, improving empirical predictive models. This study provides a new case history to the limited suite of (approximately 30) liquefaction failure case histories available for post-liquefaction in-situ strength predictive correlations.
This case history documents the Las Palmas gold mine tailings dam failure, resulting from seismic-induced liquefaction during the moment magnitude 8.8 February 27, 2010 Maule, Chile earthquake; the sixth largest since 1900. Forensic analysis provides reasonably well-constrained values of 1) back-calculated representative post-liquefaction residual strength, 2) representative penetration resistance, and 3) representative vertical effective stress along the suspected liquefied failure surface.
This study employs the incremental momentum method to incorporate momentum effects of a moving soil mass. The incremental momentum method requires a series of cross sections animating the geometry of failure progression from initiation to termination, converging on the observed final geometry. Using interpreted soil strength characteristics, an iterative procedure approximates the back-calculated value of post-liquefaction residual strength.
Findings of this case history plot well with existing empirical deterministic regression charts and are in general agreement with previous, related efforts. Results yield representative, well-constrained values of: 1) post-liquefaction residual strength ≈ 173 psf, 2) penetration resistance of N1,60,CS ≈ 5 and N1,60 ≈ 2.5, and 3) vertical effective stress ≈ 4,300 lb/ft2, or ≈ 2.0 atm.
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