With the help of Maptek BlastLogic software, mines can improve drill and blast processes and increase coal recovery.
The Bowen Basin in Queensland is known for its high grade coking coal. However, these rich deposits bring the challenge of complex geology (folds, faults and seam dips exceeding 30 degrees).
Through-seam blasting involves mining in level benches at a consistent depth across the pit. Each bench contains waste material and coal seams. The through-seam method typically requires drilling to a fixed depth, and digging in a series of smaller benches.
Benches containing waste and coal have a high risk for dilution when digging. Care must be taken when loading explosives to ensure that coal seams remain intact.
Several factors must be considered when creating a through-seam drill design, including drill access, explosives loading around coal, timing and and the same factors on the next bench. One of the most important considerations is where the explosives will sit relative to the coal.
An optimum powder factor can be selected based on historical shots, and is used to dictate drill burden and spacing. A key factor when calculating these is to ensure the powder factor is maintained in areas where stemming is added through coal areas. Because explosives are not required in coal, a smaller burden and spacing are indicated.
An explosives loading rule is created to handle complicated through-seam designs. These rules generally dictate how much stemming should be loaded through coal and at the surface, and the type of explosives for wet and dry conditions.
The design then must be successfully executed. Tracking the execution progress ensures that any learnings are passed along for future blasts. The first step is the drill bench preparation. If drills do not have access to where holes are needed, the blast is off to a bad start.
Through-seam explosives loading is unique for every hole in the blast and specific loading instructions are required based on where the coal is in each hole.
Any variation from the designed load plan can cause dilution of coal and ultimately reduce revenue.
The multi-process nature of blasting allows mines to make corrections at each step. For example, drilling mistakes can be corrected by adjusting explosives loading. Similarly, loading mistakes can be mitigated by adjusting the blast timing. However, these corrections can only be made if issues are caught early in the process.
A robust, easy to use tracking system is critical to the outcome of a blast.
Maptek BlastLogic can help track each process and adjust designs along the way. Instant access to data provides more time for review and analysis. Detecting issues early on helps avoid the costly mistakes which can be associated with large complicated blasts.
BlastLogic interfaces with site drilling navigation systems to automatically retrieve as-drilled data. With live information, engineers can review any changes to the explosives loading plan as soon as the holes are drilled.
Engineers can also easily track the progress of drilling and change plans as needed. Complex charge plans can be pre-programmed to adapt to drilling changes. This saves time and reduces delays in getting updated information to the blast crews.
Importantly, information on the performance of a blast can be used to design future blasts. It may take several attempts to optimise the blast, and keeping good records guides long-term improvement.