February 2010

Strategic mine planning

Finding the optimal in pursuit of the ideal

By R. Bergen

Innovation relies on execution – a team confers at IAMGOLD’s joint venture Sadiola Gold Mine.

At one point during the Second World War, researchers took another look at what colour Britain’s Royal Air Force should paint its bombers. The prevailing wisdom that led the planes to be black, it turned out, was wrong. In fact white planes are harder to spot against a night sky.

The review of strategy also prompted a change in the detonation depth of its explosives and the RAF’s efficiency in crippling German U-boats doubled. “There can be few cases where such a great operational gain had been obtained by such a small and simple change of tactics,” wrote a physicist who contributed to a number of such adaptations during the war.

These innovations didn’t introduce new technology but rather, they made better use of available resources. Progress came from challenging and systematically testing what had previously seemed assured.

After the war, this research approach was adopted by civilian industry, mining included. Operations research, as it came to be known, showed how things can be done better. For the mining industry, it planted the seeds that have grown into strategic mine planning, a discipline that at its core matches mining operations to long-term strategic objectives. It relies on the knowledge and collaboration of every arm of the mining operation, including finance, geology, mining and production scheduling, processing, engineering and human resources; the informed application of optimization tools. It also calls for a clear strategic vision for the company. Capturing and managing all of these aspects with a defined goal in mind can spark a shift in thinking, and counter-intuitive approaches that can effect:

  • how and when minerals are extracted;
  • how facilities are designed and where they are installed; and
  • how much value is ultimately realized.

The latest recession toppled many assumptions. A dedicated strategic mine planning approach will test the assumptions still intact. How far will conventional standards take us? Where can new, substantial value be found?

A durable solution

Forty-five years ago, the CIM Bulletin had a radical answer. Helmut Lerchs’ and Ingo Grossman’s paper, “Optimum Design of Open Pit Mines,” outlined an algorithm based on graph theory that could help planners determine the ultimate limits of an open pit mine in three dimensions by maximizing “the difference between the total mine value of ore extracted and the total extraction cost of ore and waste.”

But even as the two IBM researchers opened up a new frontier in optimization, they also traced its limits. Markets, processing facilities, mining methods, production scheduling, transport options, they noted, had, and continue to have, a bearing on plans. “There is an intimate relationship between all the above points, and it is meaningless to consider any one component of planning separately,” they wrote. “A mathematical model taking into account all possible alternatives simultaneously would, however, be of formidable size and its solution would be beyond the means of present know-how.”

Over the decades, a cascade of algorithms and new optimization programming methods — led by Jeff Whittle’s efficient implementation of the Lerchs-Grossman algorithm in a commercial software package — along with the efforts of software designers and the exponential increase in the power of the tools at their disposal have pushed the boundaries of know-how.

“The advances in computer capacity — the speed — have enabled us to bring down the processing time,” says Cindy Tonkin, technical product manager for Gemcom, which markets Whittle software. “Models that once took days can take minutes. That provides us with the ability to examine multiple options, to look at scenarios to determine a mine plan that can take us into the future — or a range of different futures — but to be robust enough to deliver value in that range of futures. We can generate optimizing models that are now up to three gigabytes. That would have been unheard of 15 years ago.”

The scope and complexity of optimization applications that serve the strategic mine planning process continue to grow. Australia-based Whittle Consulting is pressing ahead with a third version of Prober, an in-house proprietary global optimizer. Prober combines an algorithm with linear programming to create an optimized schedule that addresses a litany of issues including ultimate pit limits, mining methods, schedules, equipment needs, cut-off grades and blending. Twenty-five years ago, the optimization software that Jeff Whittle first developed for the market using the Lerchs-Grossman algorithm could calculate one option for pit design alone.

“Way back,” says Jeff Whittle, “I used to talk about a program such that each morning, you fed into it all the latest production figures, drill results, costs and prices, etc. It then thought a bit before telling you precisely where to mine today — optimally! I dubbed it ‘The Hallelujah Program.’ I don’t expect to see such a program in my lifetime, — [Whittle is now in his 80s] — but we can work towards it, and Prober is a step along the way.”

Page 1 of 3. Next
Post a comment


PDF Version