Open pit mines present a harsh and dangerous environment- for machinery and for workers. They also pose a particular challenge for global navigation satellite system (GNSS) technology-especially regarding the issue of blocked and reflected satellite signals that increase as mining equipment nears the steep pit walls (Figure 1).
Nonetheless, mining is an industry that demands operational reliability, consistency, and the kind of precision that GNSS brings. This is particularly true when it comes to blast hole drilling operations: the better a mine can control quality at the tip of the drill, the less time and handling of mined material that is needed-not to mention reduced wear and tear on downstream processing equipment.
Most mines attempt to blast holes within 20-30 centimetres (8-12 inches) of the mine plan, both horizontally and vertically. Horizontal hole spacing is critical to controlling rock fragmentation. The service life of the crushers used in processing the blasted materials (ore and waste rock) can be reduced if fragments are too large or if too much fine material is produced. Hole depth is important for creating a flat bench for subsequent mining activities. Designing the bench with a slight slope helps to improve water drainage, while a relatively flat bench reduces machine wear.
Flanders and ARDVARC®
Flanders Inc., is an Evansville, Indiana-based privately owned, third-generation manufacturer of motors, power systems, and automation solutions used in industrial operations around the world. Flanders developed its ARDVARC (Advanced Rotary Drill Vector Automated Radio Control) kit to give mine operators reliable, consistent automated drilling capabilities to ensure quality control. The advanced drilling system relies on NovAtel's GNSS receiver technology for ultra-precise positioning of drill holes-a major factor in optimizing the processing of mined materials.
Jarrid Cima, manager of software development for Flanders, points out that the development of the ARDVARC® system was driven by two factors. The first is safety: if no human operator is physically operating the drill onboard, it avoids exposure to an unsafe, collapse- prone environment. The second is productivity: an improvement of up to 30 percent can be realized.
The ARDVARC system's built-in intelligence is engineered to optimize machine movements and drill positioning. Above all, the system can be used to optimize a mine's operational profitability. It stores data related to the amount of energy required to create each blast hole. The data is then used to refine blasting procedures and optimize fragmentation of the materials being mined, which in turn affects the rest of the mining process.
The ARDVARC® operator can call up an overhead view of the drill and X cursors indicating the location of nearby target hole coordinates and the current drill steel location (Figure 2). For most of the ARDVARC® kits deployed, the operator stops the drill with the two cursors aligned as closely as possible before simply pressing a button to drill.
The system handles any of the various maneuvers required in drilling. These include raising the drill onto its corner jacks and leveling it, lowering the drill bit to detect the elevation of the surface, “collaring the hole” (a technique used to stabilize the borehole during drilling), backing out and re-drilling to clear any clogs, retracting the drill steel and drill bit once the hole is completed, and lowering the drill off of the jacks for tramming-that is, relocation of equipment between holes.
While drilling, the system records the precise position of the hole, its exact elevation, and foot-by-foot readings on the amount of required drilling force. This data reveals the geotechnical information about the rock being drilled, which can then be used to design blast patterns in the future.
By removing variables that might otherwise be introduced by operators, the system maximizes production quantity and quality. The system also optimizes the use of human resources, especially at remote mines where attracting the necessary semi-skilled talent is difficult.
“ARDVARC® can be installed drill,” Flanders sales manager Jim Elkins says, another plus for Flanders customers because most mines operate more than one type of drill. The ARDVARC® system monitors hole profile data and hole quality and integrity. The system also tracks production and records and builds reports for immediate display at the control center.