During Feasibility Stage, typically a very limited number of tests are conducted to support the mill design. This is because the tests are expensive and time consuming. As a result, these do not capture the full variability of the rock types across the entire deposit. This can have significant consequences on mill performance. https://www.cumtn.com/wp-content/uploads/2016/08/Oct_2014Upfront.pdf
During exploration, definition and extraction, widespread drilling occurs at every mine site. During drilling, every rock type is ground presenting an opportunity to better understand the variation of mechanical rock properties across the entire deposit.
Leveraging the drilling data, presents an opportunity for cost savings related to;
- Mill design and production
- Blast optimization
- Open pit/Underground mine design
and also presents an opportunity for testing and refining geological models.
There are four drilling parameters that are used to analyse drillability; torque, revolutions per minute (RPM), rate of penetration (ROP), and weight on bit (WOB). Three component accelerometers can be used to measure vibrations near the drill bit, which often correlates well with rock mechanical properties. There are numerous drillability parameters, which combine the four drilling parameters, into one representative parameter. One such parameter is the Mechanical Specific Energy (MSE), which is presented in the figures to the right, and below, and correlates well with rock mechanical properties.
In the figures to the right, and below, the drillability parameter (MSE) and maximum lateral acceleration correlate well with the Unconfined Compressive Strength (UCS) of the rock. Additionally, the maximum lateral acceleration is almost as good as the Gamma log at defining lithological boundaries.
Open Pit Mining Application
The example above demonstrates the usefulness of drilling data for characterizing the mechanical properties of rock. However, for this example, data only exists for one borehole. The figure to the right presents an example where drilling data was collected for over 100,000 10 meter blast holes in an open pit mine. By applying the same methodology, as for the example above, drillability information about a massive volume of rock was extracted.