A project report submitted to the Faculty of Engineering, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Master of Science in Engineering. / The flushing flow rate required to maximise penetration rate of holes drilled by rotary percussion is dependant on drilling parameters and chip size. Experimental work to determine the optimal flushing water flow rate for two common drilling situations was undertaken. It consisted of drilling, analysis of chip samples and flow visualization. A computer modal to predict flow rate was developed. Its output and the experimental results Were combined to explain the relationship between penetration rate and flow rate. All chips should be fiushed from the gap between the bit and the end of the hole in the time between hammer blows (ie. - within the duration of a percussion cycle). As flow rate increases, flushing improves and therefore penetration rate increases. Once flushing is adequate there is no mechanism for further increases in penetration rate, thus it remains constant and independent of further increases in flow. / Andrew Chakane 2018

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Amphibolites from several localities have been studied chemically. The rocks were spectrographically analyzed for Cr, V, Ni, Co, Sc, Zr, Sr, and Ba and major element analyses were done on 20 amphibolites, sediments, and igneous rocks. The chemistry of sediments and igneous rocks which right isochemically metamorphose to amphibolite has been studied. Discriminant function analyses were performed on major and minor elements, to classify rocks of known and unknown origins. / Thesis / Master of Science (MS)

A research report submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science in Engineering / Tunnelling projects in the weak Kalahari rock masses of the Northern Cape, South Africa present significant design challenges for both large and small-scale excavations. Most of the design of tunnelling and support carried out at present in the Kalahari is based on experience, analytical and empirical methods. The approach typically makes use of limited geotechnical information from the project site.The Kalahari basin is a complex geotechnical environment. Tunnelling projects are sensitive to the variable ground and groundwater conditions. A detailed site investigation to establish the geological and geotechnical model is critical in the selection of the appropriate excavation method and tunnel design. A review of early tunnelling projects revealed that in situ stresses and water infiltration is a long-term stability concern for inadequately lined tunnels through the red clay and weathered rock masses.This project explores the use of numerical modelling to predict the expected failure modes of the weak rock masses, with emphasis placed on concrete liner support for maintaining stability. The support models are analysed using 2D numerical models to determine the Factor of Safety of the liner. A support design criterion for reinforced and unreinforced concrete is introduced and appliedto the models to evaluate the lining thickness. The effect of using 2D plane strain models instead of3D analysis was also investigated. The total displacement of numerical models built in RS2 wascompared to RS3 models. / NG (2020)

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