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In recent years a number of research centres have endeavoured to provide a mathematical model that indicates the chief characteristics of ore flow in the sublevel caving mining method. Optimization of the design parameters for sublevel caving has ensued with the objective of maximizing ore recovery while minimizing waste dilution. Past studies have been confined by two simplifying assumptions: that the region of flow be approximated by a simple mathematical function, and that the flow analysis is static, ie extraction is calculated by employing an idealized ore-waste boundary position for each ring. Further investigation into models of ore flow has been stimulated on two counts.1. full scale tests have indicated that a more complex description is required;2. as a design tool, a dynamic analysis that monitors the displacement of the broken rock mass during extraction would yield more realistic recovery predictions under operating conditions, and enable variations on the method to be evaluated.This study reviews the various formulations currently available, or being developed to describe the flow of granular material. A viable solution in a mining context would be three dimensional, time dependent, and incorporate stress conditions. Although workers in diverse fields have analyzed the problem no solution exists at present. The majority of studies are either empirical in nature, or deficient in one or other of the above criteria. Two approaches are developed and implemented on a digital computer:(i) stochastic flow model(ii) empirical flow model based on the results of modelling studies, and full scale test. Although a number of concepts introduced in these models remain to be verified, the validity of these models would be measured by their success or failure as a simulation tool in a mining environment.

A project report submitted to the Faculty of Engineering, University of the Witwatersrand, in partial fulfilment of the requirements for the degree of Master of Science in Engineering. Johannesburg, 1997. / Due to the extreme costs of establishing new shaft systems in Witwatersrand gold mines it is essential that the resource estimation is optimised, The result of poor Of sub-optimal estimation could be catastrophic even.to the largest of mining companies. This project examines the application of Compound Lognormal Distribution theory and shows the advantages of this distribution model over more traditional models, for the Carbon Leader Reef. The incorporation of information from mined out areas of a deposit in resource estimation is demonstrated. The critical role played by accurate geological modelling is highlighted. The process of Macro Co-Kriging in conjunction with Compound Lognormal Theory is discussed in detail and is shown to be a more accurate estimation technique than traditional techniques using Lognormal theory. Finally the use of the Macro Co-kriged limits are shown to be useful in the classification of Mineral Resources. / AC2017

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A research report submitted to the Faculty of Engineering and the Build Environment, University of the Witwatersrand, in partial fulfillment of the requirements for the degree of Master of Science in Engineering Johannesburg, 2014 / The South African power crisis and corresponding rising costs experienced since 2008, created a paradigm shift in terms of electricity use. The mining sector is the second highest consumer of electricity with metalliferous mines being accountable for 80% of the total power. Recent studies revealed that underground ventilation and cooling accounts for 30% to 40% of total electricity costs in an underground metalliferous mine. Hence the need to look at ways to reduce electricity consumption in ventilation and cooling. Work has been done on optimising efficiencies of ventilation and refrigeration systems of underground mines. Currently, the high energy consumption is driven by efforts to achieve a thermally acceptable environment for workers (manned) in deep metalliferous mines which is currently between 27ºC (wb) and 29ºC (wb). However, no detailed study has been done looking at increasing thermally acceptable environments for deep level metalliferous mine. In this study the impact of increasing rejection temperature to 40ºC (db) was assessed in the automated (unmanned) scenario at a maximum depth of 2811 metres. Then the power demand was compared with the manned scenario. The results proved that automation in an underground mine has the potential of reducing electricity cost of ventilation and cooling by more than 50%. For example, the production rate of about 200 kilo-tons per month yield an annual cost saving of R71 million on electricity. These cost savings can be used to justify automation systems. Automation removes workers from the hazardous environment and replaces them with equipment which can withstand harsher conditions. The introduction of an automation system in underground mines would not come risk-free. Currently, automation systems have not yet reached a level of removing workers completely from underground.There are instances that would require workers to enter production zones. A Bow-Tie risk analysis was used to show the hazards that workers would be exposed to and prevention controls and responses to mitigate the impact the risks. / MT2017

The results of a study to model a circular mine shaft constructed in a time-dependent medium are presented. The construction sequence is considered as well as the time-dependent properties of the media around the shaft. The loads acting on the shaft liner are due to excavation of the shaft material and to the loads relieved from the media onto the liner. The results show the importance of considering the time-dependent behavior of media. The analysis was carried out using the Finite Element Method. Axisymmetric triangular and quadrilateral elements were used to model the medium, and axisymmetric shell elements were used to model the liner. The construction sequence was modeled by analyzing the system under small load increments where each load increment represents a construction step. The time behavior was modeled by using the initial strain method, which assigns a different strain value for each element in the medium. The strains are transferred to stresses and then to forces, and an incremental process is started to cover the time range desired. The results for a 400-foot shaft are shown, and changes in liner stresses were monitored as time passes. Different rock materials were modeled by using different constants in the creep law. Some materials showed significant changes in the results, and others did not. The liner horizontal displacement, and horizontal and vertical stresses increased when material constants for rock salt and anhydrite were used. Stresses in the elements adjacent to the liner decreased as time passed by, and some even went into a tensile stress site. A comparison between two solutions, one representing a multi-step construction sequence and another representing an instantaneous construction of the lined shaft, showed that liner stresses are much higher when the construction sequence is not modeled. This is due to the fact that when the excavation is modeled the forces representing the construction sequence are applied to the medium. In the other case, the forces are directly applied to the liner.

The mechanics of massive interseam failure in a multiple seam mine was investigated using three approaches: case studies, physical models and computer analysis. Specific examples of multi-seam mines with the underlying seam mined first prior to the mining of the overlying seam were studied with some design guidelines drawn from them. A loading frame capable of testing model blocks of 24 inches by 24 inches by 6 inches and also capable of applying up to a maximum of 10,000 psi of pressure on the models was designed and built. In this investigation, factors that affect the stability of the overlying seam when the underlying seam is mined first were studied using the finite element method and the Mohr-Coulomb failure criteria. Critical failure surfaces obtained from the computer analysis were analyzed for columnized and staggered pillars in room and pillar mining with the columnized pillars favored over the staggered ones. / Master of Science

Thesis (M.Eng.(Mining Engineering))--University of Pretoria, 2000. / Abstract in English. Includes bibliographical references.