Underground stope optimization with network flow method

A new algorithm to optimize stope design for the sublevel stoping mining method is described. The model is based on a cylindrical coordinate defined around the initial vertical raise. Geotechnical constraints on hanging wall and footwall slopes are translated as precedence relations between blocks in the cylindrical coordinate system. Two control parameters with clear engineering meaning are defined to further constrain the solution: (a) the maximum distance of a block from the raise and (b) the horizontal width required to bring the farthest block to the raise. The graph obtained is completed by the addition of a source and a sink node allowing to transform the optimization program to a problem of maximum flow over the graph. The (conditional) optimal stope corresponding to the current raise location and height is obtained. The best location and height for the raise are determined by global optimization. The performance of the algorithm is evaluated with three simple synthetic deposits and one real deposit. Comparison is made with the floating stope technique. The results show that the algorithm effectively meets the geotechnical constraints and control parameters, and produce realistic optimal stope for engineering use.