The encyclopedia · R&D & Science · Operational decision · 2023–2026
Rio Tinto solved decades-long open-pit mine plans with large neighborhood search
Rio Tinto's planners used large neighborhood search to crack long-term open-pit mine planning models that solvers couldn't touch — worth millions in insights.
Rio Tinto
The solution
Open-pit mine planning over decades of extraction produces enormous, complex optimization models: pit sequencing, blending, equipment, and ore grades all interact. Off-the-shelf solvers either time out or exhaust memory, so planners fell back on few-scenario manual analysis.
The team's large neighborhood search solves the problem the other way: a sliding-window heuristic produces an initial feasible plan, then repeated restricted mixed-integer solves free only a subset of variables per iteration. Neighborhood formation strategies exploit the model's structure to choose which variables to free.
Running live at Rio Tinto, the approach solves large long-term planning models that commercial solvers could not handle, cutting solve times dramatically and enabling planners to test multiple scenarios — generating millions of dollars in value insights.
Why it worked
- Fixing most variables makes each subproblem small enough to solve exactly, while iterating over different neighborhoods escapes the local traps a single greedy pass would hit.
- Structure-aware neighborhoods (blocks, benches, time periods) free the variables that actually interact, so the iteration converges fast.
- Scenario exploration is the real product: planners can now ask 'what if' across many futures instead of rationing three runs.
What can be applied
When a model is too big to solve, don't shrink the question — fix most of the answer and re-solve a moving neighborhood of decisions until it converges.
Aftermath
Published in the INFORMS Journal on Applied Analytics in 2026. Rio Tinto uses the framework for long-term mine planning, with the paper reporting 'millions of dollars in value insights' generated by the faster scenario exploration.
Sources
- Long-Term Open-Pit Mine Planning with Large Neighborhood Search
- Long-Term Open-Pit Mine Planning with Large Neighborhood Search
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