One thing that is certain in Australian underground mining is that our projects are getting deeper! Take my workplace at Gwalia, just outside Leonora. It bottoms out at 1800m below the surface, with plans to expand deeper in the coming decade. With these deeper and more complex mines come stricter protocols around geotechnical ground conditions, ventilation and as a result over all mine design.
Geotechnical constraints at depth can be overcome in multiple ways. It generally involves the utilisation of multiple systems of ground support concurrently, to provide adequate protection for miners and equipment. One that is often the backbone of any ground support standard at depth though, is shotcrete. The sprayable concrete mixture applied via a mobile spraying unit to areas that require extra support.
Many mines in the Goldfields, and beyond, will now utilise shotcrete with every cut advanced. It becomes an added part of the cycle of work between bogging of blasted dirt, and the jumbo installing bolts and mesh to the mining front. This addition to the mining cycle can cause extended cycle times and delays in meters advanced.
One way that projects can streamline and deliver repeatable quality of shotcrete, is utilising survey scanning data of their drives. Hexagon Geosystems have developed a simple to use mobile scanning system that can deliver analysis of shotcrete in situ. The user-friendly interface allows either the nozzleman, or a shift boss, to scan a heading before application of shotcrete and then again following a spray. Then, the built-in ruggedised tablet app, “Inspect Surfaces”, can be used to see a heat map of change (thickness of shotcrete) between the two scanned datasets.
This allows the operator to check for any discrepancies between desired design thickness and actual applied thickness, whilst still setup at the spraying front. This allows for improved QA/QC of shotcrete application as the crew can ensure they have met the minimum design thickness requirements, whilst not entering potentially hazardous, recently sprayed and unsupported work areas. Further to this, it will allow the nozzleman to gain valuable feedback on their spraying practices. This may possibly reduce overspray through insights delivered by datasets.
The knock-on effect of this could not only be better record keeping of each application, but also the ability to reduce wastage and over spray. This could dramatically reduce hold ups due to shotcrete application, as each load delivered to the spray hopper could be utilised to its full potential, covering more applications with similar agitator tramming time.
The data can even be geospatially referenced if required by utilising local survey control. Alternatively, the data can be stored in an arbitrary position, or multiple scans can automatically align themselves via “cloud to cloud”, which aligns multiple point clouds utilising common features of overlapping scans.
This scanning solution is not only suited for the single shotcrete application outlined above, but it can also be used for general survey purposes underground or areas of special interest within the mine. One such example could be utilising the scanning and cloud comparison functionality to assist with geotechnical assessment of areas. This could be particularly useful for areas that may need ongoing review for possible convergence due to seismic activities. Scan data can be particularly useful to show the full digital image of the area of interest.
This intuitive system utilises Leica Geosystems hardware & software, which has been the underground survey industry standard for well beyond the past decade. It combines their short range BLK360 scanner and ruggedised CS35 tablet to deliver a tailor made wireless solution for shotcrete operations. The kits include all accessories you could want for some of the harshest underground mining conditions, including a protective carry case, survey legs and all associated batteries.
Hexagon Geosystems have developed this system specifically for the growing number of projects using shotcrete underground – utilising proven hardware within its survey range. It would be awesome to see this adopted across the industry, empowering nozzlemen to refine their craft and ultimately delivering safer, more efficient mining at depth.
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