Infrastructure Engineering - Theses

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Author: Baczynski, Norbert Richard Przemyslaw × End date: 1989 × Start date: 1980 ×

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    Rock mass characterization and its application to assessment of unsupported underground openings
    Baczynski, Norbert Richard Przemyslaw ( 1980)
    The research study centres on the stability assessment of unsupported, sub-level open stopes located within the silver-lead-zinc orebodies at the Mount Isa Mine in Queensland, Australia. A systematic approach is adopted for characterization of rock masses and a statistically-based model is formulated to account for local variability in geological structure. Investigations suggest that the degree of fracture clustering observed in some masses may not have resulted from a random process. A zonal model is proposed for spatial distribution of these weakness planes. The general validity of the assumed model with respect to the dolomitic shales at the mine is confirmed by computer simulation of fracture distributions within three-dimensional blocks. The computer program used in the simulation process has been developed as part of the project. Mechanical properties of the mass are derived on the basis of the statistical model for geological structure and various published rock mass classification systems. A computer program is used to expedite these analyses. Alternate approaches for derivation of properties are mentioned. Several techniques are employed to assess the significance of statistically variable material properties on stability of the stapes. These include rock mass classifications, two-dimensional finite elements with elasto-plastic behaviour and sequential excavation, and the probability of failure analysis. Limitations of each technique are discussed. Some consideration is given to broadly reviewing past mining experience within stapes at the mine. Results of analyses demonstrate that a greater depth of understanding and appreciation of rock mass behaviour may be gained from modes with locally variable material properties. A reasonable degree of correlation is achieved between model and prototype response.