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The research for this thesis was carried out to investigate the effects of anisotropy on stress and strain measurements made by the Leeman "doorstopper" technique. The stress field in rock is influenced by many different sources. These complicate the methods for obtaining a stress tensor which is a representive model of the in-situ stress condition. Research has been carried out to determine stress concentrations for the Leeman doorstopper technique in isotropic ground, but previously, no values were known to exist for anisotropic conditions. A three-dimensional finite-element computer model was used to investigate the effect of anisotropy on stress and strain concentration factors. Displacement data and strain concentration factors obtained from this analysis, although not quantitatively accurate, showed that the doorstopper technique can indicate erroneous stress levels in anisotropic ground unless the appropriate corrections can be made. / Applied Science, Faculty of / Mining Engineering, Keevil Institute of / Graduate

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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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published_or_final_version / abstract / Civil Engineering / Doctoral / Doctor of Philosophy

Thesis (doctoral)--Monash University, 2000. / Contains two volumes.

Thesis (Ph. D.)--University of Hong Kong, 2005. / Title proper from title frame. Also available in printed format.