A Fast Optimum Pit Limit Analysis Method Based on Revised Maximum Flow Algorithm

摘要

A fast algorithm to find the optimum ultimate pit is not only used to solve the ultimate pit limit problem that maximize total dollar value for a given block model of an open pit project but it also plays an important role in solving a series of optimum pit limits required for some other stages of mine planning, e.g., open pit phase design using parameterization and long-term open pit mine production scheduling using Lagrangian relaxation (Dagdelen, 1985) or four-dimensional network relaxation (Akaike, 1999) methods. This paper presents the revised maximum flow algorithm that is further developed in order to solve each sub-problem in a new open pit mine phase design algorithm (Somrit, 2011) based on the maximum flow algorithm proposed by Johnson (Johnson, 1968). For all case studies, results indicate that the revised maximum flow algorithm is much faster than widely used commercial software packages that employ the Lerchs-Grossman (LG) algorithm (Lerchs & Grossman, 1965). We also prove that the optimality of the ultimate pit limit problem is always obtained using the revised maximum flow algorithm. Furthermore, results confirm that this algorithm guarantees the true optimum ultimate pit limit while some commercial software packages surprisingly may not.