Hovermap maintains safety at Northparkes

Located outside Parkes in regional New South Wales, CMOC’s Northparkes mine is one of Australia’s largest copper producers. It was Australia’s first block cave mine when mining commenced in 1997.

Northparkes has earned a reputation for industry innovation, and in 2015 became the world’s most automated underground mine.

In 2020, the operation produced 26,997 tonnes of copper and 20,897 ounces of gold.

Challenges

In 2018, Northparkes commenced a ventilation upgrade to support planned mine expansion of the E26L1N block cave, supplement underground air volumes and maintain occupational exposure to respirable dust and quartz silica at acceptable limits.

The upgraded mine ventilation system consists of two primary exhaust shafts (E26 and E48). Each has two fans mounted on surface, and primary air intakes are the main decline, the hoisting shaft and the E48 intake shaft.

Intake and exhaust shafts, each measuring 5m in diameter and 560m deep were raise bored adjacent to the site’s operational E48 block cave and in proximity to sections of the mine slated for future development.

Both ventilation shafts experienced partial failure at the lower level, shortly after completion. Efforts to stabilise the more badly affected intake shaft by lining it with shotcrete were unsuccessful and self-mining continues to occur in the failed section.

A ventilation incline linking the intact section of the exhaust shaft with the mine workings was subsequently developed, as an alternative return airway.

The Northparkes geotechnical team needed to monitor the condition of both ventilation shafts to ensure they remained viable and to protect the integrity of the vent incline.

Access constraints meant the only way to inspect the failed sections was to send a scanner down the shafts.

While the mine possessed a downhole bore camera, it could only generate images, not the detailed data the engineering team needed to make informed planning and remediation decisions.

Solution

In June 2021, Northparkes conducted a scan to measure deformation and self-mining of the intake shaft using the emesent Hovermap LiDAR scanner.

Hovermap is a smart mobile scanning unit that combines advanced collision avoidance and autonomous flight technologies to map hazardous and GPS-denied environments.

Hovermap, mounted in a protective cage, was lowered 560 m down the intake shaft on a cable attached to a franna crane.

It is uniquely versatile, it can be mounted to a drone, cage, backpack or vehicle to map challenging, inaccessible areas. With a wide range of applications, Hovermap is being used by customers around the world.

Change detection image depicts the difference between scans conducted 12 months apart. Cold colours indicate failed areas, where the void is expanding. The image provides important insights into how the void is changing shape, the areas that are moving, and the failure zones.

An earlier Hovermap scan was undertaken on May 2020, when Northparkes engaged Pybar Mining Services to scan the intake shaft.

Northparkes acquired a Hovermap unit in June 2021 so its survey and geotechnical engineering team could conduct their own regular inspections.

The Hovermap scanner was mounted in a protective cage, attached to a crane and lowered slowly down the ventilation shaft. Scans were carried out in both directions and took around two hours to complete. Point cloud data was exported from Hovermap to the Deswik mine planning software platform where change detection and deformation were analysed.

Results

Northparkes personnel were able to measure changes in shaft over-break and deformation over time.

Comparing two scans, from 2020 and 2021, enabled them to detect changes in the raise bore walls. They were also able to identify joints, fractures and other types of rock features that may affect the stability of the shafts and impact the ventilation incline in the future.

Access to accurate data representing the true shape and dimensions of each shaft allows mine personnel to monitor the integrity of the ventilation system.

Better intelligence makes it possible to take timely remedial action when early signs of failure are detected and before the stability of the return air incline shaft is compromised. This improved preparedness reduces the occurrence of costly mine shutdowns and the resultant production loss.

About Ray Chan

Editor of industrial titles and mastheads with Prime Creative Media. Publications include Rail Express and Australian Mining (web content).

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