Boral’s Ormeau Quarry is in the northern Gold Coast region of Queensland, in a large zone of meta-greywacke. It supplies high quality aggregates to the asphalt and concrete market of southeast Queensland.
The current site capacity is about 400,000 tonnes per annum. The site recently had a development application approved to increase its capacity to two million tonnes. A project to realise this capacity has begun.
To ensure the pit development could meet the capacity requirements of the site, Boral and Orica worked together to:
• Improve blast size and shape.
• Optimise blast performance.
• Reduce the overall cost per blasted tonne of rock.
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BUSINESS IMPROVEMENT PROGRAM
A key element of the explosives supply agreement between Boral and Orica is the business improvement program. Through this program, Boral and Orica work through a defined process to scope, evaluate and deliver projects with significant value to Boral’s quarry operations.
A team was formed including members of Orica’s blast extraction planning team and key experts from Boral, to develop a project charter.
Initial investigations showed 17 blasts had been fired in the previous financial year to meet the production requirements for that year. It was also determined that:
• The blasts were not optimally sized.
• Orica surveyors were visiting the site more than once for each blast.
The team developed five project objectives:
• To optimise blast size to minimise the overall cost per tonne of rock blasted.
• To reduce blast days per calendar year.
• To deliver required volume and blend of raw feed to meet plant capacity.
• To ensure environmental compliance in line with licence conditions for blasting.
• To ensure compliance with approve life of mine design and any interim staged designs.
The key project outcome was to develop an easily interpretable schedule to meet the objectives stated above, while providing the quarry manager with confidence in the delivery of required rock for current and future plant production requirements.
TECHNICAL SOLUTIONS
Orica’s blast extraction planning team used several tools to deliver the objectives above. They included:
• The GEOVIA Surpac mine design software.
• Orica’s SHOTPlus 5 blast design software.
• Orica’s blast scheduling tool.
• Orica’s Cycad vibration analysis software.
With these tools, a series of optimised blast blocks was first developed, after determining potential blast locations and obtaining the most current design and topographic models.
Several considerations needed to be taken into account when building the blast blocks.
These included:
• The required extraction rate.
• The optimised blast volume.
• The blast geometry.
• Compliance with the life of mine design.
• Environmental compliance factors.
• Health and safety requirements.
• Final product quality parameters.
A number of schedule options were then created based on specifically identified drivers for the site.
These options were evaluated using Orica’s blast scheduling tool, allowing the most effective blast extraction plan to be determined from a productivity, blending and cost perspective. An example output from the scheduling tool is provided in
The schedule was then developed into a blast extraction plan that was colour-coded, making it easy to use for all personnel
(see Figure 2).
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Following development of the blast extraction plan, it was possible to identify and assess any environmentally sensitive blasts and take early action to ensure blasts were designed to comply with environmental limits, without affecting the blast extraction plan.
RESULTS
Working together, Boral and Orica were able to:
• Increase the size of blasts, reducing blast days per year from 17 to five, which in turn increased the utilisation of Orica’s mobile manufacturing units by 50 per cent.
• Reduce blasting costs by more than 20 per cent (see Figure 3).
In addition to these benefits:
• A consistent crusher feed was maintained at the blend ratios required by the quarry.
• Blasts have been designed to take imposed environmental limits into account while maintaining the blast extraction plan.
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The upper benches have been realigned to match the levels specified in the life of
mine design.
CUSTOMER FEEDBACK
Boral Quarries said its personnel recognised the benefits of developing a 12 month extraction plan for Ormeau Quarry that fit within the parameters of the life of mine design and provided the quarry manager and business with a fit for purpose document that optimised the extraction process, with clear actions and outcomes that met the company’s operational requirements.
The planned capacity increase for the site promises to be a step change, having a rolling 12 month extraction plan that helps the business to plan around pit development and associated activities to meet Boral’s operational and commercial targets.
The project charter approach involving critical stakeholders, plus use of mine development tools and techniques such as GEOVIA Surpac and Orica’s SHOTPlus 5, were significant enablers for the project to achieve its ongoing objectives.
Karen Normanton is a senior technical services engineer for Orica. •
ACKNOWLEDGEMENTS
Orica thanks Neil Bellamy, Boral’s Queensland and Northern Territory drill and blast manager, and Liam Elsworth, the Boral Ormeau Quarry manager, for their strong collaboration and support throughout the project and for permission to publish this case study.