GA Simulation for Grade Adjustment in Limestone Quarries

Abstract eng:
In limestone quarries that produce lime for steel makers or slaked lime for purification, the products must satisfy the permitted CaO grade limits. In some limestone quarries in Japan, limestone with a low CaO grade is blended with high CaO grade limestone in order to maintain high product quality. Ito and Nishiyama (2003) and Ito et al. (2010) tried to apply a genetic algorithm (GA) in a mining procedure simulation for grade control and achieved better combination results. However, these simulations did not consider the stability of working faces during operations. It is very important to consider the safety of operations in open-pit mines in addition to the management of product quality. Then, in order to determine the optimum mixing of blocks with low and high CaO grade considering safety of the working face during operations in quarries, a mining procedure simulation applying a GA process was developed for an assumed mining area. The following are the basic quarry assumptions: (i) number of removable blocks is 6,000, (ii) block size is 6m square and 10m high, (iii) mining area is the lateral side of a mountain, (iv) highest altitude is 100m (i.e., 10 levels), and (v) average density is 2.5. Each block is distributed an appropriate CaO grade ranged 40-57%. One product lot consists of 5 blocks and needs to satisfy CaO grade of 50%. The whole area of 6,000 blocks could be mined out in one year, that is, 500 blocks (100 lots) are mined in a month. The simulation was conducted for the following two conditions: (1) whole blocks were mined in sequence (whole mining condition), and (2) the mining area was first divided into four appropriate areas considering the safety of working faces (quarterly mining condition). As a result, it was revealed that there were no marked differences in the number of production lots not satisfying the permitted grade between the two conditions. On the other hand, the working face situation during the operations was quite different between the two conditions. It was revealed that the setting of intermediate targets for mining blocks in advance is an effective way to manage the safety of the mining procedure.

• Export as: BibTeX | MARC | MARCXML | DC | EndNote | NLM | RefWorks
• Add to your basket