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Fragmentation analysis opens way for new plant design

Deer Park Quarry is a major component of Boral’s Melbourne supply chain. The 1100-hectare site is located off the Western Freeway, relatively close to both the Melbourne CBD and the rapidly developing outer western suburbs.

The quarry produces a variety of aggregate and roadbase products from the Western Plains basalt resource. It is a key asset for Boral, and will play a vital role in the company’s growth in Victoria.

To safeguard the quarry’s future, Boral recently decided to replace its fixed plant, which was built in the 1960s and is nearing the end of its service life. To do this, Boral will design and construct a new crushing and screening circuit as part of the Deer Park Quarry Plant Replacement Project.

The columnar basalt quarried at Deer Park is challenging when blasted because it tends to produce oversize boulders from the face and stemming zone, and finer particles within the rock mass. It was crucial that the fixed plant supplier designed the crushing plant specifically to suit these geological characteristics.

Typically, raw crusher feed gradations, determined by manually sorting and sieving a sample of blasted rock into designated size envelopes, would be used to do this. However, due to the safety aspects of sorting and measuring large lump sizes (up to two metres), the determination of the gradations, and to provide a more accurate and repeatable data set, Boral enlisted Orica’s assistance through its Powersieve fragmentation analysis software, plus technical advice and peer review.


Technical solutions

Powersieve is a proprietary software program developed by Orica to measure the fragmentation characteristics of broken rock. The program analyses scaled digital images, grouping material into particle size windows specified by the operator. This data is then used to build gradation curves that describe the overall fragmentation of the muckpile.

Compared with traditional techniques, Powersieve provides a very safe, efficient and thorough method of analysing large volumes of material.

In the past the program has primarily been used to optimise blast designs, so a specific gradation can be targeted to suit the primary crusher at a given site.

However, in this application Powersieve was used to measure the as-blastedfragmentation, so the new processing plant could be tailored to suit site-specific geology, which optimises crushing efficiency and lowers the overall cost of production.

Boral’s engineering team for the Deer Park Quarry Plant Replacement Project undertook the photography and image processing.

They analysed four blasts in three different zones of the quarry, to ensure the sample was representative of the Deer Park resource. The technique and results were verified by Dr Mike Noy of Orica, to ensure their accuracy and validity.


Results and feedback

The Powersieve fragmentation analysis provided detailed gradation curves that showed a higher concentration of fine material in the raw feed than previously understood.

The fixed plant design was reviewed and subsequently modified to accommodate what was learnt through the Powersieve analysis.

“Orica Powersieve software has allowed Boral to formulate a reliable raw feed gradation using a safe, repeatable process, minimising human error,” Boral Construction Materials engineer Michael Oppedisano said.

“Design and engineering works for the new quarry fixed plant can now be based on best practice methods for determining feed gradation, which will assist in commissioning the new plant and generating products as designed.”

Graham Gordon is the blasting engineer for Orica Quarry Services.
Orica thanks Boral Construction Materials for its support and permission to publish this case study.

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