Safex Newsletter No.82 May 2025

In alignment with our previous newsletters, we commence our articles with a safety message from Gilles de Preux, the CEO of the SEE Group, headquartered in Switzerland.

We are pleased to announce the introduction of a new member to our Board of Governors. Christo Peltz from AECI Mining will be succeeding Neil Franklin, who has stepped down due to work commitments.

Progress on our website is being prioritized under the leadership of Andy Begg, Paulo Siquera, and Ludovic Turlin. A Basis of Safety section is now operational, and significant advancements have been made on the Safety Management System. Articles regarding both initiatives are presented by Andy and Paulo.

Johanne dela Rovere from EPC presents an article on the reinforcement of windows to withstand overpressure. An assessment of the resistance of installations to blast waves typically indicates that glazed joinery and glazing are prevalent weak points in infrastructure.

Diane Ginnane elaborates on a Safety Management System developed by Dyno Nobel. Dyno Nobel has introduced an innovative Explosives Management System (ExMS) that emphasizes the identification and management of critical activities, while establishing standards and procedures that define minimum requirements for all operations related to explosives and the security of sensitive hazardous substances.

From South Africa, BME’s Dr. Ramesh Dhoorgapersadh addresses risk management in reactive ground. Reactive ground refers to soil containing high concentrations of sulfides (typically iron or copper) that have the potential to react exothermically with ammonium nitrate-based explosives.

Johanne recently delivered a presentation at a technical conference in Belgium focused on SAFEX and the associated database. In her preparation, she identified key areas for improvement, which were subsequently communicated to the webmaster.

NIXT, a Corporate Associate Member in South Africa, successfully hosted a conference in April, during which they agreed to feature two presentations in our Newsletter. One presentation will cover the Track and Trace of Explosives by Rob Penny from Synertech, while the other will discuss the application of fungi in environmental cleanup, presented by Northwest University in collaboration with Dyno Nobel and Sasol.

The current list of Board Initiatives is accessible on the homepage of the website. Should any member wish to contribute to these work groups, please feel free to reach out to me.

We are pleased to announce that our upcoming Newsletter will be published at the end of October 2025. A reminder will be distributed to solicit contributions from industry professionals.

Additionally, we would like to remind you of our triannual Congress taking place in Lisbon in April 2026. The organization of this significant event in our calendar is progressing well. We are currently seeking a few more papers on incidents for discussion during our Member Day. Please reach out to me if you are interested in representing your company.

Until we meet again, please remain vigilant and prioritize your safety.

Risk Management of Reactive Ground

Dr. Ramesh Dhoorgapersadh

Reactive ground is the term used to describe ground that contains high concentrations of sulphides (usually iron or coper) with the potential to react exothermically with ammonium nitrate-based explosives. This spontaneous chemical reaction involves the oxidation of sulphides by nitrates resulting in a quick and unstable rise in temperature. These unexpected and often intense reactions can lead to premature or unplanned initiation of explosives and toxic gas emissions, making reactive ground one of the most hazardous conditions in mining. The hazardous nature of reactive ground not only poses a threat to mining operations but can also lead to catastrophic accidents, including fatalities, injuries, and significant environmental damage. Therefore, identifying and addressing the risks associated with reactive ground is crucial for protecting both human lives and operational continuity.

Conducting geotechnical studies helps identify areas with reactive ground, enabling the implementation of targeted mitigation approaches. Reactivity screening can identify if site samples have the potential to react with ammonium nitrate explosives and can be used to determine the reactivity levels across the block. The assessment provides insights that can be used to manage reactive ground conditions and form the foundation of risk assessments and safety protocols that are specific to the site conditions.

Where reactive ground is found to be eminent, a risk assessment must be conducted and communicated with employees before any work is conducted in the area. The risk assessment should include assessing the compatibility of the selected explosive with the level of reactivity of the ground and adapting mitigation strategies such as using urea inhibited emulsion explosives or explosives and initiating products that are compatible with reactive ground and are formulated to withstand elevated temperatures. Monitoring controls of critical parameters such as temperature during the charging process should also be included in the risk assessment as controls to quickly identify and address changes in ground conditions.

Protocols to manage drill cuttings and preventing this from falling into blast holes is also a simple but key safety measure to mitigate the risks associated with reactive ground. Removing or clearing drill cuttings around the collar of the blast hole lowers the chance of cuttings mixing with explosives, thereby reducing the risk of a temperature buildup or explosive reactions.

Sleeving, a process whereby a plastic lining is applied to blast holes as a barrier between the reactive sulphides in blast hole walls and the explosives can be used to prevent exothermic reactions and unplanned detonations. This process does have limitations whereby the liner can split, or bulk explosives can split between the sides of the liner resulting in exposure of explosives to reactive ground. It is therefore important to note that the application of sleeves should be carefully evaluated especially with the use of uninhibited emulsion explosives.

In blasting operations involving reactive ground, managing the materials used for stemming is required to prevent unintended reactions between the stemming material and the explosive, reducing the risk of premature detonation. It is best practice to ensure that stemming material is tested to confirm that it is free of any reactive material. Unstemmed blast holes release any heat generated after the addition of explosives. To allow this, stemming should be the final step before blasting. However, blasting with unstemmed blast holes can lead to increased air blast and fly rock and the risks associated with this must be carefully considered against the benefits of heat release.

The number of people on the block during charging and stemming processes should be kept to a minimum. Personnel working on the block must be trained on monitoring and observing blast holes for signs of reactivity. These signs include the emission of fumes, smoke and unpleasant odours from the collar of the blast hole. Adequate emergency response and evacuation plans must be in place in the event that signs of reactive ground are observed or detected during blasting activities. The plans must be clearly communicated to all personnel working on the block and rehearsed or mock drills should be conducted to verify the awareness level of personnel and adequacy of emergency response systems.

Unplanned detonations resulting from reactive ground can have severe consequences. By implementing robust monitoring processes, including the regular review and update of risk assessments for sites with known reactive ground, mining operations can significantly reduce the likelihood of such incidents. Establishing and adhering to specific operational procedures for charging activities in reactive ground areas, coupled with ensuring that personnel are thoroughly trained and equipped to handle these conditions, are also essential measures to help prevent incidents.

References

  • Australian Explosives Industry and Safety Group Inc. (2017) Code of Practice: Elevated Temperature and Reactive Ground. Edition 4. March.
  • Pieterse, D. and Small, G. (n.d.) Reactive Ground Blast Management in a South Africa Open Pit Zinc Mine. [online] Available at: https://beacon.by/teracore/reactive-ground-blast-management-in-a-south-africa-open-pit-zinc-mine?t=1742388395
  • Oates, T.E. and Spiteri, W. 2021 Stemming and best practice in the mining industry: A literature review. Journal of the Southern African Institute of Mining and Metallurgy, vol. 121, no. 8, pp. 415–426
  • White, R. (2022) Reactive Ground and Explosives. [online] Available at: https://iseeaustralia.org/wp-content/uploads/2022/08/3_1White_ReactiveGroundandExplosives-1.pdf
  • Valenta, R., O’Sullivan, R. and Clark, A. (2019) 'Prediction of reactive ground using geoscientific datasets'. GEOMIN-MINEPLANNING 2019. WH Bryan Mining and Geology Research Centre – Sustainable Minerals Institute, The University of Queensland, Australia; Julius Kruttschnitt Mineral Research Centre – Sustainable Minerals Institute, The University of Queensland, Australia.