A New approach to 3-dimensional optimization of ultimate pit geometry for open pit mines with variable overall slope angles

Altuntov, Firdevs Kübra
The mining activities have high economic risks and the determination of the optimum ultimate pit limit of an ore body greatly affects the economic feasibility of an open pit mine. Due to necessity of determining optimum pit limit, many researchers proposed different algorithms and heuristic methods which maximize economic value of a mine while satisfying operational constraints and extraction sequence constraints. In most of the proposed methods, overall slope angle variation in the pit is constant. However, in real situations, overall slope angle varies in different parts of the mine due to geotechnical reasons. Since overall slope angle is an important constraint in open pit optimization and it is a significant factor in terms of slope stability, overall slope angle variation should be taken into consideration in optimization algorithms. In previous studies, methods that include overall slope angle variation were generally formed according to precedency relationships among blocks, but these methods also have problems in creating variable overall slope angles. To overcome this problem, in this study, it is aimed to apply a new approach which includes overall slope angle variation in optimization of ultimate pit limits. For this purpose, mixed integer programming and cubic spline interpolation were utilized, and the application was performed by coding in Python Programming Language. The proposed method was verified by applying it to the four case studies.