Underground Mining
In an effort to enhance mine safety, Beaconsfield Gold Mine, at Beaconsfield, north-east Tasmania, worked with Hi-Tech Metrology to develop a remotely controlled means of scanning stopes.
Historically, Beaconsfield's mine surveying team, headed by Simon Arthur, chief surveyor, has been restricted to using older-generation technologies, such as cavity monitoring systems (CMS) which have been around in the industry for 10 to 15 years. These systems are slow, require two-men to operate the equipment, and only collect a limited amount of data. Access to restricted stopes in the mine is limited by the boom length of the CMS and visibility of the area above the brow is virtually impossible.
After the serious incident underground on Anzac Day in 2006, when tragically one miner was killed, and another two were trapped at the 830 level for 10-days, mine management have been single-minded in their determination to improve mine safety.
With this in mind Simon was keen to find a way in which to survey stopes underground in the mine - more safely, and had heard about some new scanning technology, and hence was interested to see whether this technology could be applied to the conditions at Beaconsfield.
Beaconsfield, as part of the safety improvement program, was also about to introduce a new tele-remote system for bogging-out stopes underground, using a specially prepared CAT R1300G mining loader. At this point Simon Arthur approached Hi-Tech Metrology about the possibility of using a terrestrial laser scanner for an underground surveying application.
Hi-Tech Metrology took up the challenge of applying the technology of a high-precision 3D spatial laser scanning system in the harsh, arduous conditions of an underground gold mine.
The product chosen for the application, the FARO LS880 laser scanning system, is a 3D spatial information capturing system that collects data at a rate of 120,000 points per second at a distance of up to 80 metes from the scanner. The accuracy of the scan data collected is quoted as +/-3mm over a 25 metre distance.
The FARO scanner is motor driven on a horizontal axis giving it a 360 degree field of view in the horizontal plane, and a 320 degree field of view in the vertical plane. In fact the only spatial data the FARO LS Scanner can't pick-up is the information on what is underneath the base of the scanner - that is the tripod or whatever is used to mount the scanner.
Initially, the thoughts were to send the scanner into the inaccessible stope area using a specially-designed, remote controlled buggy or cart, as this had previously been done overseas but Simon Arthur was keen to use the tele-remote loader as the means of "delivering" the scanner into the mine stopes.
This presented some challenges to the development team, which consisted of members from Beaconsfield's survey, electrical and maintenance groups as well as Hi-Tech Metrology application's specialists back in Melbourne.
Initially it was thought that issues concerning excessive vibration, water and dust, and potential damage from rock falls would be the major challenges, but these turned out to be relatively easy to resolve, particularly compared to the communications issues.
The Beaconsfield underground maintenance team developed a special-purpose box to house the laser scanner which was mounted inside the loader bucket, using a gimbal mounting system. Special isolation mounts to mount the scanner to the mounting box in order to minimize vibration transfer and to provide a level of dampening for the FARO Scanner, were also designed and built by the maintenance group at Beaconsfield Gold Mine.
Initially it was thought that communications between the laser scanner in loader bucket would be via either an extra channel on the analogue tele-remote communications system or alternatively through an "expendable" cable system along the drive.
However both of these options were not ideal and the search for a wireless solution became a high priority. This presented a significant challenge for the team as it was desirable to control the remote scanning of a stope independently of the loader, with the scanner mounted in the bucket of the loader, and this would require wireless communications from the loader back to a laptop computer.
Hi-Tech Metrology eventually solved the communications issues after a number of investigations and final on-site testing of Rajant Technologies' "BreadCrumb" Wi-Fi products, supplied locally in Australia by Mine Site Technologies.
The solution involved the establishment of a mobile Wi-Fi mesh system underground. This consisted of a Rajant BreadCrumb personal unit, mounted to the cabin of the loader, and which was connected with a simple CAT5 cable to the FARO laser scanner and mobile battery pack. Another two Rajant SE Breadcrumb units were hung from the walls of the drives allowing wireless communications back to a remote laptop computer at the tele-remote station for data upload and operation of the scanner.After a number of trials underground the data collection and communication system was proven to the satisfaction of Beaconsfield Gold Mine the team then moved onto the next phase, data processing.
The enormous amount of spatial data collected by the FARO LS Scanner needs to be processed in the supplied software with the scanner, a product called FARO Scene. This software registers the multiple scans taken in a session; imports mine coordinates of the reference points along the drives which have been picked-up with a total station during surveying, and filters any extraneous data.
Once the scans are registered, processed, and reduced in size the data is converted to a triangulated STL mesh format for export. The STL mesh files are then imported into the Mine's CAD system, Surpac, where volume calculations can be made as to the volume of material that has been removed from the stope compared to both the theoretical stope volume and the amount of material believed to have been mined by the mining group for the month.
According to Simon Arthur other significant benefits of this technology in an underground mining environment, particularly due to clarity of the data, is that it now allows the geo-technical engineers at the mine to assess the safety or otherwise of the stope area.
It is also reported by Simon Arthur that, armed with the FARO LS laser scanning system tools, surveying underground is now a "one-man" operation, as opposed to the two-men needed with the CMS, and so there is a real cost saving for the mine as well with the adoption of this technology. The FARO Laser Scanner is also very affordable, and depending on options, can be lower in cost than a CMS system, but offers significant faster data collection and far better stope visualization tools.
After a number of months of use now at Beaconsfield, other benefits have been found with the use of the laser scanning system; such as the ability to assess stopes for areas where the mining has been incomplete, and this allows the mining groups to take decisions on whether to go back into the stope and recommence bogging or not.
Whilst the Beaconsfield experience with the use of laser scanning is still in its early stages, the management of the mine have already seen the benefits of the use of this technology, and are also keen to apply the technology to other applications within the mine now that the equipment is on-site and the personnel at Beaconsfield are experienced in the use of the equipment and the subsequent post-scanning data processing. Management has talked about using the technology for surveying other parts of the mine, such as the mines decline, for use in walk-through animations and 3D models for investors visitors and other interested paries.
Beaconsfield is also able to use the FARO laser scanner for other "more typical" uses of the technology such as scanning underground plant and equipment in order to develop "as built" drawings for plant and equipment that have been incrementally installed underground over a number of years or else for assessing whether new plant and equipment will fit into the available areas before the cost and time of taking new plant and equipment underground occurs. Survey applications on the surface are also possible with the LS Scanner including plant infrastructure as well as for applications in the Mines mill and ore processing plant.
Other improvements and enhancements to the application of laser scanning at Beaconsfield is on-going between Beaconsfield Gold Mining and Hi-Tech Metrology. Such developments include additional scanning protection systems, additional communications options and future delivery systems of the laser scanning technology in underground applications etc. where tele-remote equipment is either not available or suitable for the particular situation.
These on-going developments will ensure that the ground-breaking achievements that have been made at Beaconsfield Gold Mine continue to provide financial benefits and enhanced operational safety of the mine. They also stand as a great testament to the ingenuity of the industry in applying new and innovative technologies in a novel way benefiting both productivity and mine safety.