Alert no. 111 | 05 April 2023 | Version 1

Unplanned Detonation of Explosives During Rock Breaking Activity

What happened?

An unplanned detonation of misfired explosives occurred when an excavator fitted with a rock-breaker attachment impacted explosives. The operator was shaken but unharmed.

How did it happen?

An unbroken toe in the floor was identified more than a year after a shot was fired in the quarry. Several secondary blasts were fired to break oversize fragments in the same area.

The unbroken toe was blasted along with another secondary blast for oversize rocks. Misfire in the toe was not identified and hence not marked for subsequent digging or rock breaking operations.

Inadequate records of secondary blasting meant the operator did not know the ground being broken contained misfired explosives, and subsequently the rock breaker hit the booster/detonator.

Key issues

• Unplanned initiation of explosives is a critical hazard to the safety of people. Detonators and boosters contain sensitive explosives which can explode when impacted by machinery or equipment.
• Processes on site failed to identify and remediate a misfire.
• Available records for multiple secondary blasts of oversized material contained deficient information to determine:
  • the exact blast parameters involving the toe and oversized rocks.
  • the number of oversized rocks and the toe holes fired in the same blast.
  • the type and quantity of explosives loaded into oversized rocks and toe holes.
  • an accurate record of the tie-up pattern and timing pattern of the initiation system used.

Recommendations

• Shotfirers must complete accurate blast records to the standards prescribed in section 153 of the Queensland Explosives Regulation 2017.
• Shotfirers must inspect the area immediately after clearing the blast to identify any misfires which must be refired or marked clearly for subsequent operations. This process should be captured in the safety management procedures.
• Authority holders employing shotfirers must be able to demonstrate that effective systems have been implemented to enable statutory obligations of shotfirers to be fulfilled.

References and further information

1. Queensland Explosives Act 1999
2. Queensland Explosives Regulation 2017
3. Mining and Quarrying Safety and Health Act 1999
4. Mining and Quarrying Safety and Health Regulation 2017
5. Australian Standard 2187 Part 2 – Use of Explosives

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Authorised by Hermann Fasching - chief-inspector-explosives

Contact: Shane Cooper, Senior Inspector of Explosives , +61 7 3199 8023 explosives@rshq.qld.gov.au

Issued by Resources Safety & Health Queensland

Safety: This information is a guide only and is issued to promote safety through experience. It is not to be taken as a statement of law and must not be construed to waive or modify any legal obligation.

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