Profile
Material: Coal
Bench Height: 6.0 m
Stemming: 3.7 m
Burden: 7.0 m
Spacing: 7.0 m
Bore Diameter: 0.171 m
Explosives: ANFO
Challenge
Suboptimal Productivity in the Upper Layer
At a coal mine in South Kalimantan, hard rock layers in the upper layer caused poor fragmentation, prolonged excavation times, missed production targets, and increased costs due to repetitive work cycles. Initial attempts to change the blasting design from 7x7x6 m (45 kg) to 7x7x7 m (60 kg) yielded only slight improvements, but resulted in higher vibration risks, and the overburden remained suboptimal. With powder factor limits in place and vibration safety measures in place, the Drill Blast team on site, in collaboration with MTi Group and PT Prima Minechem Indonesia, found a solution to increase stemming effectiveness without increasing the explosive charge. Technical evaluations led to the implementation of air decking using BLASTBAG KRAKATAU™ as a more efficient and safe solution.
Solution
Air Decking Using MTi BLASTBAG™
The trial was conducted in three structured stages to measure the impact of the air deck on fragmentation, energy efficiency, and productivity.
To ensure objectivity, a series of KPIs were established considering four key elements:
| Stage | Blasting Pattern | Method |
|---|---|---|
| POC 1 | 7m x 7m x 6m | No deck vs with deck |
| POC 2 | 6m x 7m x 6m | No deck vs with deck |
| Optimization | 6,5m x 8m x 6m | All blast holes use decks |
To ensure objectivity, a series of KPIs was established considering four key elements:
- Excavation time – Target set at 10 seconds or less
- Powder factor – Target below 0.15 kg/Bcm
- Maximum explosive charge – 45 kgs
- Fragmentation target – Top layer size remains below 500 mm
Results
Better Fragmentation, Lower Costs
The use of the KRAKATAU™ BLASTBAG has a significant impact on excavation performance and blast quality, as seen in the following table and the accompanying graph.
| PARAMETER | IMPROVEMENT |
|---|---|
| P80 | Down 8% |
| XMAX | Down 21% |
| EXCAVATION SPEED | Improved by 21% |
| DRILLING AND BLASTING COSTS | Down 8% |
| FLYROCK | Significantly Reduced |
| CONFINEMENT LEVEL | More Stable |
Based on these blasting results, the advantages of BLASTBAG™ are as follows:
- Reduces upward pressure during stemming
- Releases energy more effectively into hard rock masses
- Maintains a safe powder factor limit (<45 kg)
- Develops blast energy centrally, increasing fragmentation
The application of BLASTBAG™ also allows for optimized hole depth from 6.0 m to 7.0 m while maintaining constant explosive consumption, resulting in drilling efficiency.
Conclusion
Optimal Productivity Returns Without Increasing Risk
The comprehensive implementation of the air deck using BLASTBAG KRAKATAU™ provides:
- Dramatically increased excavation productivity
- Lower operational costs
- Safe vibration levels
- Controlled flyrock
- Optimized hard layer fragmentation without increasing explosive charges
The client now uses BLASTBAG KRAKATAU™ for all production blasting operations, resulting in accelerated overburden removal with more cost-effectiveness and consistent excavation quality.
