Development of limit state design for rock engineering in fractured rock masses

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This research will tackle the important and timely issue in geotechnical engineering of establishing limit state design (LSD) protocols for use in rock engineering. It will be of direct benefit to engineers by providing new tools and techniques, to society by permitting more economic and reliable designs, and to engineering science through the development of improved understanding of the engineering performance of fractured rock masses. In civil engineering, the many benefits brought by LSD principles in terms of improved economy and reliability have been recognised for many years. Over the last two decades these principles have been developed for application in geotechnical engineering, with the result that structures such as foundations and slopes in soil are now optimally designed using limit state concepts. However, for any engineering in fractured rock -- be it for highway rock slopes, transportation tunnels, underground mining operations or any other purpose -- robust application of LSD is not possible, with the result that sub-optimal design methods have to be employed. The principal reason why LSD cannot currently be applied to rock masses is the uncertainty associated with the fractures they contain. This uncertainty includes their location, orientation and mechanical properties such as strength, as well as the effect they have on aspects such as the stress induced in a rock mass and the affect this has on strength and stability. To date, LSD in geotechnical engineering has assumed that random variation -- so-called aleatoric uncertainty -- describes the variability of soil properties. However, for fractured rocks it is epistemic uncertainty -- a lack of information or knowledge -- that is critical. Thus, and drawing on continuing developments in both applied mathematics and other fields of engineering, this research will establish means by which the epistemic uncertainty inherent in fractured rock masses can be handled, thereby leading to the development of radically improved design methods.