Rapid generation of multiple designs allows mine planners to quickly generate a suite of plans for caving methods, detailed production schedules and simulated “what-if” design scenarios.
Let’s talk Block Caving, because for all the industry talk nowadays of digital transformation, block cave mining presents an interesting new idea. The basic underground operation hasn’t changed in many decades. What has changed are current economics, digital tools and new modeling methods to better plan and manage operations.
Imagine an open pit and heavy machines hauling material up from increasing depths. Now imagine an underground mirror image. In this image, a vertical (or close to vertical) underground column of ore is undermined from below to collapse under its own weight and loaded in vehicles and conveyors that haul the material to the surface.
Block cave mining is becoming increasingly attractive for open pit operations struggling to find orebodies close to the earth’s surface. And for new projects, cave mining requires a much smaller footprint and generates less waste.
Mitigating Uncertainty
Generally best suited for lower grade ore reserves, block caving involves an elaborate pre-construction process that can take several years to develop, with considerable upfront capital expenditure. However, once production begins, the cost of block cave mining is as low as open pit mining, about one-tenth the cost of conventional underground methods. Production rates can reach 30,000 to 100,000 tons per day, a comparable rate for an open pit processing plant. Drilling and blasting costs are far less, and there are no backfilling costs. Block caving sharply reduces surface waste disposal compared with open pit operations because the amount of waste rock generated from block caving is far less.
Still, block cave production often entails uncertainties. In early stages of caving projects, little is known about underground orebody characteristics. This makes it difficult to develop accurate input parameters for mine design and strategy, and that makes it difficult to predict a mine’s future performance. Fortunately, new methods to optimize production scheduling can help overcome many uncertainties while minimizing risk.
Today, engineers have developed modeling software tools, methods, and templates that make it easy to quickly generate multiple designs and schedules that cover the likely range of key parameters. This rapid generation of multiple designs and plans, as opposed to evaluating only a few or even a single case based on precise but inaccurate parameter assumptions, allows mine planners to quickly generate a suite of designs and schedules that optimizes the decision-making process, reduce risk by running simulated “what-if” scenarios, and create detailed production schedules to maximize the net present value of the project.
Future of Mining?
Some have begun to refer to block cave mining as the “the deep mining method of the future.” Worldwide, about fifty block cave mining projects are underway today, and consortiums such as Cave Mining 2040 are working to reduce lead times and capital investment, improve viability, safety, cost, production, and to win public support.
In a new five-part series on block cave mining, we take a closer look, including: where to start; footprint and Best Height of Draw (BHOD); material flow; mining sequence and production schedule; and, very important, continual updating, monitoring, and improving operations throughout the mine’s life. We hope you find this series useful.
Firouz Khodayari is an industry consultant, author, and professional engineer with a PhD in mining engineering and more than a decade of international mine planning and optimization experience. He specializes in mathematical modelling and production schedule optimization for open pit and underground mining.
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