Modification of Lerchs and Grossmann Algorithm for Pit Limit Optimization with Slopes Less Than 1:1

The Lerchs and Grossmann algorithm is a rigorous technique Based on Dynamic Programming, developed for optimization of open pit limits. This algorithm guarantees the true optimum solutions in 2D sections, but is may be used only for pit slope constraints of 1:1, 2:1 or more. In circumstances, where the geomechanical conditions impose less slopes such as 1:2, an adjustment of the block sizes and reconstruction of the block model is needed. A new algorithm is introduced in this paper to overcome this shortcoming. The conventional block model is transformed into an intermediate and a final block model to reflect the pit slope constraints. Then the modified Lerchs and Grossmann algorithm consisting of a recursive formula with two criteria is implemented on the final model. Using this algorithm, there is no need for reconstruction of the block model.