At the SME MineXchange conference in February 2020, Coeur Mining reviewed its automation journey so far at the Coeur Alaska Kensington gold mine, whichis located about 45 miles NW of Juneau. The mine started production in July 2010 and passed 1 Moz by 2019. The mine produces gold concentrate for smelter refining and has been progressively implementing LHD automation & digitalisation in the form of data analytics and remote process control at the site. The impetus was that the operating costs are high due to the mine’s location (for example parts take a week to get to site from Seattle), so the company was seeking to improve efficiencies and make better use of downtime safety between blasts and be able to continue mucking during these 1 to 1.5 hour shift change periods when currently nothing is produced.
The move would also allow the equipment to better follow a surveyed tramming route, removing pauses and waits for example in tighter corners, while at the same time improving safety with collision avoidance technology. Using onboard LIDAR with collision avoidance tech and a pre-programmed route would allow running of LHDs at maximum optimal speeds without risk of damage. The mine also wanted an increased ability to track equipment location, which cuts down time loss at the beginning of shifts; and to have the ability track power usage at or near the face, as well as more finite costing analysis. The company also wanted to track miners better for safety reasons in the event of an incident. Ventilation on demand (VOD) was also a desired capability at the face. The company also wanted to track water treatment underground and control pumping remotely. Equipment wise Coeur wanted telemetry and real time monitoring capabilities plus earlier warnings of failure on a real time basis. It would also mean safer remote operation in active stopes and more informed decision making.
The company knew there would be an additional cost to going with automation but proceeded on the basis of the associated efficiencies that would be gained. Sandvik’s AutoMine was chosen as the mine was going into a fleet upgrade cycle. Sandvik was chosen as they had the systems ready to go that allowed Kensington to implement it quickly. The automation was already on the machine as opposed to having to be retrofitted. It offered the ability to use remote operation using radio control if needed, as well as teleremote operation if needed. The main usage would be semi autonomous with mucking still remotely done but tramming fully autonomously as well as ore pass dumping. Kensington mine also chose to add Sandvik’ OptiMine digitalisation solution for tracking, allowing monitoring of any incorrect equipment usage, predictive maintenance, better understand utilisation and improve productivity.
All this required investment in a new wireless network underground, and to keep costs down, this WiFi network has been designed and maintained to allow use of alternative sources for key replacement parts such as cabling. It has also been kept flexible in design, with fast installation as the mining areas to develop and to allow for upgrades when required. The network is also monitored remotely for any defects to minimise the need for underground inspection. Despite teething problems and initial issues with user acceptance the system now functions beyond original expectations and has met all the original requirements.
In 2019 Kensington moved some 4,000 t of ore autonomously with auto operations having started mid-year including the implementation period and installing more comms backbone to support the new autononmous areas. By late 2019/early 2020 overall acceptance of the system increased markedly and in January 2020 alone 4,000 t were moved autonomously and this rate has continued. Long range planning has also improved. The mine has traditionally operated a mixed Sandvik and Caterpillar fleet for both LHDs and underground trucks. The current automation programme builds on the mine experience with a conventional Sandvik LH514. Currently there are two 14 t capacity Sandvik LH514s equipped to operate with AutoMine but up to February 2020 only one was being used in autonomous mode. Kensington is now also able to track loads and cycle times for trucks. Three underground water treatment plants are now being controlled via the network system and VOD is being expanded to all areas.
In Kensington, transverse stoping is mainly used. The dimension is primarily 40 ft in width, a nominal height of 75 ft, and variable lengths, from 25 to 150 ft along strike. Access ramps (16 × 16 ft) and level development (15 × 15 ft) are driven in the footwall (above 910 level) or hanging wall (below 850 level) of the orebody with twin boom jumbos, LHDs and teledump low profile mine haul trucks. Ore is extracted by driving across the orebody on two levels, drilling and blasting with 60 to 80 ft vertical rings of blast holes between the two levels at a width of 40 to 50 ft and creating an open stope near perpendicular to the strike of the ore using Sandvik Cubex and Epiroc Simba longhole drills. Vertical raising within and outside of the orebody is done with the Cubex longhole drill in most instances. Where greater ground control and dimension control is desired, a raisebore of the appropriate size is selected to pilot a hole between existing excavations and then back-reamed to the desired dimension.
