Four-Dimensional Network Relaxation Method for Long-Term Open Pit Mine Scheduling

摘要

The four-dimensional (4D) network relaxation method, originally developed by Akaike in 1999,rnuses Lagrange relaxation and is known for its ability to include the price change and possible betterrnoutputs, but the computation time is huge. However, the continuous advancement in computerrntechnologies allows the use of higher-speed computers with more memory capacity. Therefore, inrnthis paper the authors have tried to implement the method with adjustments and improvementsrnin its algorithm to suit the current computing system. As a result, the computation time has beenrndrastically reduced and more constraints can be included, which makes the scheduling a morernrealistic one. The case study of an open pit gold mine with 129 500 blocks can be solved consideringrnthe capacity constraints in 71 seconds. In previous case studies, the mined ore had to be processedrnor disposed of immediately. Now, stockpiling can be included as another option. Since the details ofrnthe algorithm are still being improved, the computation time is a little longer than the previous casesrnwithout the stockpiling option. However, it is found that scheduling with the stockpiling option isrnpossible in a reasonable time. In conclusion, the 4D network relaxation method has become morernuseful with advances in computer technologies and provides better results.