ABSTRACT
Many long hole stoping methods applied in underground mines make use of rib pillars to keep stope stability. It is commonly seen stopes with 30–35 m along strike intercalated by 4–8 m length rib pillars. Depending on the situation (rock mass condition, depth, orebody thickness, etc.) around 15 to 25% of the mine’s reserves have to be left as rib pillars, especially when considered retreat methods where, after stoping, pillars are hardly reaccessed. Usually, engineers make use of a standard pattern to place rib pillars along a oredrive. Having the longest stope span possible generally means leaving fewer metal content. However, many orebodies vary along strike in terms of grade and thickness, thus varying in terms of metal content and revenue. As a consequence, regular pattern may not be the best solution. This paper aims to develop a mixed integer linear programming algorithm to optimize rib pillar placement in a sublevel oredrive.
