A fundamental problem in open pit mine planning is that of determining the optimum ultimate pit limits of the mine. These limits are that pit contour which is the result of extracting a volume of material which maximizes the difference between the value of extracted ore and the total extraction cost of ore and waste whilst satisfying certain practical operational requirements, such as. safe wall slopes. The determination of the optimum pit contour provides information which is essential in the evaluation of the economic potential of the mineral deposit.A number of optimization techniques have been proposed for determining the optimum pit contour. Of these techniques, those based on graph theory, linear programming and dynamic programming are mathematically rigorous, but only those based on graph theory are more suited to solving the three-dimensional problem. Unfortunately, direct application of these techniques to large ore- bodies may cause considerable difficulties because of the exceptionally high demand on computer storage and time requirements. Indeed, 25 years of research effort has not satisfactorily resolved these computational problems.A major contribution of the work presented in this thesis is the successful implementation of a system of techniques to solve the graph theoretic model, particularly when applied to large ore- bodies. A measure of this success is the fact that pits, as much as seven times larger may be designed with a given amount of computer storage, at a fraction of the time required by current software packages. The solution strategy presented involves the application of a modified Dinics Maximum Flow algorithm, together with an efficient data reducing technique. Computational results of these techniques applied on data from gold producing mines in Western Australia are used to demonstrate the success of this strategy.The relationships ++ / between the rigorous pit optimization techniques are also considered in this work. In particular, the Lerchs-Grossman graph-theoret ic method is shown to be stepwise equivalent to a modified version of the Dual-Simplex Linear Programming technique and not as efficient as the Network Flow method.

Thesis (M.S.)--West Virginia University, 2008. / Title from document title page. Document formatted into pages; contains vii, 32 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 29-31).

Thesis (M.S.)--University of Michigan, 1981.

Thesis (M.S.)--University of Michigan, 1998. / Includes bibliographical references.

Thesis (M.S.)--University of Michigan, 2000. / Includes bibliographical references.

Thesis (M.S.)--University of Michigan, 1981.

Thesis (M.S.)--University of Michigan, 2003. / Includes bibliographical references.

Thesis (M.S.)--University of Michigan, 2002. / Includes bibliographical references.

The evaluation of risk is often performed assuming static conditions when in reality, conditions are continually evolving. In the following dissertation, the evaluation of risk with changing conditions over time is considered for a specific project - placing overburden into an active, open pit mine. The research focuses on the geotechnical components of risk with the goal of identifying whether and to what extent it is possible to place overburden on mined out portions of the open pit slopes. The relevant factors, which change with time or impact risk, are first identified and an evaluation is performed to estimate a probability of failure at various stages of the project life. Potential damages are then assessed by first evaluating the run out distance and post failure geometry of a slope failure and then estimating the percentage of material that would have to be removed to continue extraction of ore. To convert the uncertainty into economic terms, unit values for savings that result from placing overburden in the pit and costs associated with cleaning up failure debris are estimated. The probability of failure, potential for cleanup, and unit values are combined to produce estimates of the likely costs and benefits associated with dumping overburden in the open pit.The results of the analysis indicated that risk varies considerably with time. However, it is possible to place overburden in the central portion of the open pit up to a limit of approximately 80 million tons while maintaining a positive net value of expected costs and benefits.

Dissertation (PhD)--University of Stellenbosch, 2005. / Bibliography. Also available via the Internet.