At Snowden our Mine Planning group thrives on solving complex problems quickly. Because each project is unique, we often develop our own tools to get the best bottom-line outcome for our clients. We do this by leveraging our diverse range of skills, experiences and perspectives as mining engineers, mathematicians and software developers. This series of articles provide some examples of where we have developed innovative solutions to problems; solutions that could also help add value to your project or operation.
A number of software packages have been released recently for the optimisation of mining outlines for underground stoping operations. Some of these techniques are not appropriate for block caving applications due to the unique constraints associated with this mining method. These include:
- Dilution (mixing) dynamics as material is caved
- Minimum mining footprint, usually on a single level, in order to induce caving
- Maximum column height to control dilution and stability
- Minimum column height to support development costs
- Maximum adjacent height of draw (HOD) slope angle to minimise dilution from mixing
- Minimum horizontal pillar distance to provide regional stability
These issues are shown in the images below, in plan (upper), and in section (lower).
Additionally, with such large footprints, it is often necessary to mine the cave in panels. Where possible you will want to target the highest grade panels first as this can have a large impact on project value. Thus, it is important to have a tool that not only generates your overall outline, but also provides some guidance to the caving sequence. This is akin to cutbacks in an open pit.
At Snowden, we developed Block Cave Optimisor tool to optimise the footprint and column heights for a cave, considering all these important constraints. First, it applies vertical pre-mixing to gain a more accurate view of mining grades. It also optimises at a range of cut-off grades in order to provide a nested set of outlines for panel design.
The image below shows the footprint outline in plan. The darker colours represent higher grade outlines, and the places to try and start caving. The progression as the grey colours lighten shows the potential panel expansion options. Areas outside the grey colours are potential areas for locating infrastructure.