The standard approach to open pit design is to optimize the pit shape using the criterion of maximum total profit on the basis of a revenue block model of the orebody. There are some difficult problems inherent in such an approach. For example, scheduling and production rates will have a significant effect on the shape of the pit; if the bulk of the rich (and thus high revenue earning) ore is at the bottom of the pit and will not be mined until near the end of the life of the mine, then the time value of money may make the simple revenue block approach meaningless. In
addition, optimality is a function of economic parameters which may change significantly over time.
The aim of the parametric approach is to express the solution (Le., the optimal pit shape) as a function of one or more parameters such as costs, prices or
cut-off grade. Matheron's parametric approach is to use a grade block model together with the techniques of functional analysis without making any economic
assumptions. This leads to a set of technically optimal nested pits which can be used for mine scheduling.
Whittle uses the traditional revenue block approach with the Lerchs-Grossmann algorithm and finds a set of optimal pits which are functions of the price/cost ratio.
The aim of this project is to combine the two approaches mentioned above and provide a complete parametric solution in terms of technical and economic parameters. The project includes the development of an interactive computer
program for the parametric design and scheduling of open pits.
The author reviews the literature on optimal open pit design and scheduling and then provides an overview of the parameterization method. In this research project the parameterization method has been extended to allow for the selection of an economically optimum pit. Scheduling is then discussed in detail and a new method that combines linear programming and user-activated simulation is
introduced.
All software developed during this project is described in detail in the final Chapter.