A large-scale surface coal operation in Queensland’s Bowen Basin partnered with Orica to overcome stratigraphic challenges and boost productivity.

As a multi-seam operation, the site was blasting and uncovering one seam at a time. One of the upper seams was relatively hard, and this slowed coal mining. The site sought assistance from Orica to develop a through-seam drill and blast design that would improve mining productivity in coal and overburden without compromising coal recovery.

On this site, Orica provides a Total Load Service, with Orica site-based engineers supporting daily design and supervision.

To address the situation, the site engineers and Orica devised a combined blasting approach that integrated a through-seam blast and coal blast across multiple horizons.

The key challenges in this scenario included:

• Achieving effective fragmentation of the overburden above the coal seam
• Fracturing the coal seam adequately without excessive pulverisation
• Minimising coal dilution
• Ensuring optimal fragmentation of the interburden below the seam

This design required careful consideration of blast parameters to balance fragmentation control, coal integrity, and overall excavation efficiency.

Loading through-seam blasts in dipping strata demands efficient and accurate data management. Every hole is slightly different. Variable energy charges are required between and within holes. Flexibility to rapidly change explosive energy and ensure precise explosive placement are crucial for success.

Orica’s 4D™ advanced bulk explosive system expands the range of energy available from conventional ANFO and emulsion blends. Delivered through MMU™ bulk delivery vehicles with LOADPlus™, it enables precise loading control. Integrated with the BlastIQ™ platform, it improves decision-making and blast outcomes.

In this case:

• A lower RBS charge of Aquacharge™ 4D™ was used in the coal seam
• A higher RBS was used in overburden and interburden

The initiation sequence is critical to preserving coal and reducing dilution. A layer-by-layer firing sequence using electronic delays is essential.

The i‑kon™ III electronic blasting system enables:

• Precise timing up to 30,000 ms
• Multiple blasting capability
• Controlled movement for efficient digging
• Reduced mixing of coal and overburden

All project KPIs were successfully met, confirming the effectiveness of the blast design and execution.

• Digging productivity above the coal seam exceeded target by 14%
• Productivity below the seam was 10% above target

The coal roof and floor remained intact. Coal mining performance was exceptional, with dig rates 56% higher than target. Coal recovery reached 97.7%.

These results highlight the precision achieved through integration of:

• 4D™ enabled MMU™ with LOADPlus™
• BlastIQ™ platform
• i‑kon™ III electronic blasting