| This thesis deals with some of the decisions taken in open pit long term mine planning at two levels, at the level of setting the policies and criteria for the classification of long term plans as well as at the level of the planning personnel who interpret these policies and attempt to meet criteria with the description of the volume removal sequence that forms a long term plan. A condition for the maximisation of the widely accepted criterion of present value was identified and proven. The consequences of this condition are discussed extensively with particular emphasis on a policy which, based on ore cutoff mineralisation values, would lead to maximum present value. The condition explains some of the widely accepted rules and practices in open pit mining and proves that the immediate mining and stripping costs are not relevant in setting a cutoff mineralisation value based operating policy. The effects of stockpiling on this policy are also addressed, as well as the required mine capacity and the size of the recoverable reserve, employing a multicriteria approach. The empirical work in this area addresses the incentive that an operating mining company has in modifying the current operating environment and indicates that the established mine capacity is an important decision parameter. In addition, this work indicates that the expected present value gains from operating policy changes are measurable and, sometimes, small.;Decisions on the level of the planning engineer are addressed with the development of a complete computer package, to assist in deriving and accurately describing solutions to routine tasks in open pit mine design and planning. The package makes extensive use of interactive computer graphics and utilises a simple, powerful and flexible user interface that may be used effectively in the areas of final pit limit analysis, permanent and temporary haulage road design, long term production planning as well as waste dump design.;The package has been designed to operate on both the block model and contour representations of pit limit solutions. Emphasis has been placed on the efficient use of computer resources and the functionality and ease of utilisation of the user interface. The package features an unique ramp design utility, for use in designing both permanent as well as temporary ramps. In addressing this problem, contour representations of pit limits were used, and the associated periphery problems were independently resolved in a complete and robust manner. The research in this area resulted in the development of a powerful, complete, flexible and generic software package, which has been applied at a variety of open pit operations world wide. |
