How ORB outperformed market leading planning software with a 30% increase to NPV


At one of the world's largest underground lead-zinc mines our project team were tasked with determining how to best plan and schedule development and production tasks to maximise NPV.

The team had to optimally schedule 50,000 stoping related tasks and a further 30,000 development tasks while considering multiple interdependencies and constraints, including ventilation restrictions; fill production and capacity; drilling capacity; production machinery constraints; mill tonnage and grade constraints; resource category limits; task dependencies; dependency lag timings, and so on.

The customer was already using what is generally considered to be two of the leading mine planning and mine design tools on the market. These existing incumbent tools however do not include any sophisticated mathematical optimisation techniques capable of automatically producing optimal solutions for problems of this scale and complexity. Instead they offer either ‘resource levelling algorithms’ or ‘manual dynamic scheduling algorithms’ which essentially function as manual decision making aids. Producing solutions using these tools can be inordinately time consuming, trying to satisfy all constraints, whilst keeping up production tonnes to the mill is often impossible, and maximising value is a completely manual task.

How ORB differs to other tools in the market is in how it expresses 'the problem' as a range of variables with an objective function, in this case, maximising NPV, subject to any number of constraints. No priorities are entered and no manual guidance is required to achieve an optimised solution. This is a fundamentally different approach to traditional mine planning software solution techniques for large and complex underground mining operations and this project clearly demonstrates the significant value ORB can deliver. In fact, ORB was able to produce a solution that:

  • explicitly scheduled all 80,000 production and development tasks
  • enforced more than 230 separate detailed planning constraints
  • obeyed all precedence constraints and corresponding timing lags
  • automatically produced optimal solutions using an exact numerical optimisation technique
  • increased NPV by 30% over the best solutions produced using the incumbent tools

Polymathian Partner and Project Lead, Steven Donaldson said, "Producing detailed and practical long-term mine plans for large stoping operations is an extraordinarily complex planning task. With over 80,000 individual tasks needing to be scheduled spanning a mine life exceeding 40 years, being able to increase NPV by 30% was a phenomenal result."

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