The overall objective of any geotechnical mine design procedure must be to maximize the extraction of the ore reserves while maintaining the integrity of the working areas. At the McLellan Mine the cut-and-fill mining method was first adopted. This decision was made for flexibility in the size and shape of the mine openings to allow for the variability in width and grade of the ore zone. As a result the geotechnical design of the cut-and-fill stopes necessitated investigations to evaluate the character of the rock mass with regard to the hydrogeology, lithology, structural geology, rock strength and rock mass ratings at the site and to assess the in-situ stress conditions. In addition, the character of the backfill material had to be estimated prior to detailed testing. Based upon these parameters two dimensional finite element analyses were completed, the sill pillar and the two stopes were designed. Finally, remedial rock reinforcement was recommended for suspected unstable spans. / Applied Science, Faculty of / Mining Engineering, Keevil Institute of / Graduate

The mechanisms of strata deformation due to underground mining were analyzed in an effort to better understand immediate roof behavior and surface displacements. Strata deformation characteristics above longwall and room-and-pillar mines in the eastern U.S. coalfields were evaluated and a numerical procedure was developed for calculating surface displacements. The model, based on the well-known finite element method, utilized empirical indices associated with subsidence engineering in order to incorporate the site-specific characteristics into the formulation. Different material behavior models and failure criteria were employed in an attempt to determine the areas highly deformed by underground excavation. Additionally, the method was sensitive to the ratios of the elastic moduli used to describe different rocks and/ or rock conditions, and not to the magnitude of the elastic properties. Thus, the use of arbitrary reduction factors to convert laboratory to in situ property values was completely avoided and scaling of the calculated surface displacements was based on, the empirically predicted, regional or local parameters. The use of fixed displacement nodes around an opening to induce failure overcame the roof-floor overlap problem encountered in other formulations. The successful implementation of the proposed methodology for modeling surface deformations complements and enhances existing prediction techniques, which are primarily based on empirical approaches, by allowing parametric analysis for different excavation geometrics, roof convergence curves and overburden properties. / Ph. D.

The mining of coal within 110 feet below a previously mined seam creates interaction effects which can be detrimental to work in the lower seam. These interaction effects are characterized by zones of very high stress and result in floor and roof instability and pillar crushing. Recent developments in the field of ground control make it possible to determine with a certain degree of confidence the location of these zones and estimate the degree to which the interaction will affect the lower seam. This information has been incorporated into a software package for microcomputers which will predict lower seam problems and suggest design criteria for minimizing the difficulties which will be encountered. / M.S.

A roof support system is one of the most important systems in underground mining. It may consist of various types of supports such as props, cribs, steel arches, powered supports and roof bolts, among others. In this research, powered supports and roof bolting are not included. Evaluation of underground supports needs to take account of several factors. These factors include the mechanical behavior of the supports, the interaction between the support and the surrounding strata, the cost of the support, and the overall economic results. In this research, emphasis is placed on the mechanical behavior of the supports. Criteria have been set up and, based on these criteria, a variety of supports have been evaluated. / Master of Science

The increased impact on mine subsidence during the recent years led to the development of two semi-empirical prediction methods for the eastern United States coalfields. The methods are based on an extensive data bank, which includes a total of twenty three panels, from nine case studies, which were instrumented during this research effort. An extensive field monitoring program, utilizing a digital computer tacheometer, was developed and implemented for this purpose. The first prediction method using a profile function, provides a fast and convenient method for prediction of vertical movements above mine panels of uniform geometry. More specifically the hyperbolic tangent function is utilized, as adapted to regional data. The developed model is capable of accurate general predictions for the Eastem U.S. coalfields. The second method is based on the Budryk-Knothe influence function. The parameters used in this method were mainly determined from the monitored case studies. The use of such a method requires primarily a computer, however, it can negotiate mine sections of complex conditions and can calculate subsidence as well as any other mode of deformation on the surface. For the prediction of the parameters required for the application of both methods a number of relationships between mining and subsidence factors were established through the analysis of the collected data. Computer software were developed for the analysis of the data as well as for the application of the prediction methods. / Ph. D.

Mining into strata disturbed by previous mining operations either above or below may sometimes result in severe strata control problems. These interaction problems, associated with most multiple-seam mining operations, are very common in the Appalachian coal region and are the subject of this dissertation. On the basis of both theoretical and empirical analyses, using statistical analysis, numerical modeling, and photoelastic modeling methods in conjunction with the analysis of numerous case studies, a comprehensive, integrated model has been constructed and represented by a computer program called "MSEAM”. Using this comprehensive model, possible interaction problems under certain geological and mining conditions can be first predicted based on rules determined either empirically or statistically. Then, detailed analyses using different interaction mechanisms -- pillar load transfer, arching effect, upper seam subsidence, inner- burden bending, and innerburden shearing -- can further determine the area or degree of possible interaction in both under- and over-mining situations. Special geologic and mining factors controlling interaction are also summarized by indices for an independent interaction prediction. This integrated model has been validated by back·analysis of several case studies. Full descriptions of multivariate statistical analysis, photoelastic modeling technique, quantization of various interaction mechanisms, and development of the comprehensive model are included. / Ph. D.

M.Ing. / Safety within the mining industry is a primary concern for everyone involved. More specifically, active below-ground stope support for South African Mines is becoming increasingly important due to a renewed emphasis on the safety and well-being of the people actually working underground. It is imperative that all stope support systems are rigorously tested, continuously, both under laboratory conditions and in-situ to prove their performance and manufacturing standards. The Rocprop was initially manufactured in 1995 with the first two hundred props being installed at East Driefontein Consolidated Gold Mine in the Carletonville area. In the three years since the first introduction over three hundred thousand Rocprops have been manufactured and sold to South African Mines with the number steadily increasing. The Rocprop is a tubular support consisting of two tubes — a Ø139mm 'inner' tube and a Ø152mm 'outer' tube. One end of each tube is sealed by dome ends which are welded onto the tube mouths. The two tubes, cut to identical lengths, fit inside one another and extend telescopically during installation. Once the desired height has been reached, leaving enough tube overlapping to ensure the support does not buckle, the wedge is hammered in locking the prop at that height. The water is then removed after which the prop will provide active support of the rock mass above it. One of the components responsible for the Rocprops success is a dome end. This is either a forging or a pressing welded onto each end of the support and allows continual concentric loading throughout the life of the Rocprop. At present the dome ends are pressings, manufactured into hemispheres from 10mm mild steel plate in one action. The reason for the Rocprop's success is its performance characteristics. It's all metal construction, ease of installation, reliability and predictability in both seismic and static conditions, fire resistance, blast resistant, economically viability and versatility have made the prop successful. Reasons for the research were to investigate the dome end forming process in general and to investigate current numerical analysis techniques ability to predict loads during manufacture, the final shape, spring-back and other local deformation areas. Also to investigate alternate manufacturing methods such as cold forming, which provides advantages such as better mechanical properties and higher structural capabilities. The use of alternate materials in the Rocprop manufacture has been an ongoing process for MSP, manufacturer and current licensee holder of the Rocprop. A substitute for the current dome end manufactured from mild steel was investigated. For the substitute to be viable the material should be stronger, weigh less and be cost effective. In depth knowledge about the forming of the dome end at various velocities was gathered, providing information for further optimisation of the component.

Please read the abstract in the 00front part of this document / Dissertation (MSc (Mining Engineering))--University of Pretoria, 2007. / Mining Engineering / unrestricted

The coal fields of Appalachia of many contiguously mineable coal seams. Common practice in mining multiple seams is to extract the seams in a descending order. However, the mining sequence may still be based on seam ownership, availability of the seam and the general economic situation, net on ground control considerations. One of the major ground control mechanisms that must be considered in the design of a mine is the arching of stresses around a previously mined lower seam. This investigation deals with the extent and magnitude of the stresses above an underground opening. The finite element approach was utilized to determine the extent and magnitude of stresses for various widths of mine opening, depths of cover and overburden material. This information can then be used as an approximation of the stresses that may be encountered in an actual mining situation. / Master of Science

M.Tech. (Architectural Technology) / The architectural intervention proposes an urban redevelopment along the mining belt of the city of Johannesburg through the treatment of acid mine drainage. The design research includes a network of selected sites located along the Johannesburgmining belt to address the problem of acid mine drainage,as well as to provide solutions for future urban environments. The main solutions to eradicate the acid mine water problem are infrastructural, which in most cases is associatedwith inhumane environments. A design question addressing the marriage between harsh infrast ructure and humane environments is therefore dealt with ,in an attempt to create a self-sustaining architecture in which infrastructure can have an integrative urban function for the future . The dissertation aims to achive a design intervention that will thread the traces of a mining century into this contemporary African city, through an architecture that will grow into the future of the ever-changing and continuously emergent Johannesburg.