Unplanned ore dilution or stope overbreak, which has a direct and large influence on the cost of a stope, and ultimately on the profitability of a mining operation, can be attributed to both the mining process and to geologic setting. The research undertaken in this document, applicable to a wide range of underground mines employing the blasthole mining method to extract tabular orebodies, focuses on examining factors attributable to the generation of unstable stope hanging-walls. / The primary objective of the research undertaken is to establish new models for stope and orezone design, with respect to anticipated stope overbreak, focusing on the position and type of stope within the orezone extraction sequence. Identified factors influencing unplanned dilution, such as: induced stress environment, stope geometry, and the setting of individual stopes are considered. / The research undertaken incorporates a variety of components, including (i) parametric 3-D numerical modelling to examine influences of individual factors on hanging-wall overbreak, (ii) case example analysis, and (iii) orezone extraction sequence simulation, using 3-D elastic numerical modelling. Design criteria, developed from the parametric modelling, was applied to the orezone sequence modelling to develop trends for stope dilution, as functions of stope design and construction. / It was found that hanging-wall overbreak is not significantly influenced by depth alone, and that stopes with large vertical and short horizontal dimensions or stopes having long horizontal and short vertical dimensions are more stable than large square-like stopes. Also, through parametric and case studies, it was demonstrated that, in addition to stope dimension, the amount of unplanned dilution differed according to stope type. Five stope types were identified, based on their position within a tabular blasthole mining sequence. Measured overbreak varies with stope type, with secondary stopes generating a greater volume of hanging-wall dilution than do primary stopes. A pillarless mining sequence will generate less overall dilution than a primary stope: secondary pillar mining sequence.

Thesis (Ph. D.)--Missouri University of Science and Technology, 2008. / Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed May 6, 2008) Includes bibliographical references (p. 229-235).

Thesis (Ph. D.)--West Virginia University, 2000. / Title from document title page. Document formatted into pages; contains xi, 162 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 156-161).

Thesis (Ph. D.)--West Virginia University, 2006. / Title from document title page. Document formatted into pages; contains xvi, 357 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 132-124).

Thesis (Ph. D.)--West Virginia University, 2005. / Title from document title page. Document formatted into pages; contains ix, 145 p. : ill. (some col.), maps (some col.). Vita. Includes abstract. Includes bibliographical references (p. 118-122).

Thesis (Ph. D.)--West Virginia University, 2009. / Title from document title page. Document formatted into pages; contains xx, 393 p. : ill. (some col.), maps (some col.). Vita. Includes abstract. Includes bibliographical references (p. 356-371).

This thesis is directed towards the comparison of active and passive bolts systems to reveal which system shows the most favorable behavior for improved performance, safety and cost. This was achieved through the incorporation of new technologies, field data, numerical modeling and established theories in ground control analysis. All in all, a better understanding of the quasi-static behavior of underground coal mine roofs has been attained. Over the summer of 2010, the Department of Mining and Mineral Resource Engineering at Southern Illinois University Carbondale, in conjunction with Andy Hyett of YieldPoint Inc., Peabody and the National Institute of Occupational Safety and Health (NIOSH), installed over one hundred and seventy instrumented extensometers, closure meters, shear-meters, passive rebar roof bolts, tension rebar roof bolts, and double lock rebar roof bolts at three coal mines. Two of the three coal mines were room-and-pillar mines and the other a longwall mine. Data was routinely collected over a nine-month period to analyze shearing, dilation, and axial bolt loading occurring within the rock mass, and entry closure occurring between the excavation hanging-wall and foot-wall. Based on bolt loadings, shear, axial behavior and statistical analysis, initial results indicate that active roof bolts do not show superior performance for the added cost. Active bolts seem to show no difference from passive bolts in the initial loading phase either, indicating that tension bleed-off is a concern soon after installation; however, this observation was not captured, as the data loggers were not intrinsically safe. Considering the modeling results, the trends in axial loading seem to be calibrated but the magnitudes are not. Computer modeling also shows the potential to accurately model in situ bolt performance; however, challenges remain in obtaining a good match between numerical modeling and field observations.

M.Ing. / As of 1991 new legislation demands that all existing and proposed mines have to submit and implement a rehabilitation plan. This plan consists of numerous phases and can cost a fair amount of money that almost none of the mines have budgeted for. During the rehabilitation process the improvement of the ground on, for example, discard dumps or slurry ponds, are not stable or adequate to enable the civil engineer to ensure stability for the new development. This can include a new sports field or low cost housing or just the peace of mind that the dump is stable and looks natural. This thesis will aim to introduce some of the numerous different ground improvement techniques that are available in South Africa and overseas.

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