The case for blasthole drill automation

Semi-autonomous drill operation, managed from a tablet computer.
CREDIT: CATERPILLAR

Material fragmentation has compounding effects on mining costs and productivity. Drilling and blasting results impact loading, hauling and crushing and play a significant role in the success of the total mining system.

At the start of the mining cycle, where the rock mass is drilled and blasted, the degree of fragmentation and the muck pile configuration are determined, as are the effects on cost and productivity of all subsequent operations. Consider the cost of managing oversize material – including secondary handling, overloading, reduced diggability, higher load factors, extra pass loading, increased machine wear and reduced throughput rates. Also consider how improper bench slopes and uneven floors slow loading and hauling.

When we automate the drill, we can lower the variability in drilling so that the mine receives quality holes that match the designed drill-and-blast patterns. Additionally, with automation and on-board communications, we can off-load key data that can be used to track formation variations in real-time – enabling mine managers to take actions that mitigate potential risks to the production schedule. For example:

• Make adjustments to the drill pattern (spacing, burden, hole depth, hole angle)
• Make adjustments to the blasting mix (powder factor, timing, stemming material used)
• Make adjustments to the downstream load-and-haul operation and/or processing plan

The drill automation journey is one that can be taken in incremental steps.

Building blocks matched to needs

Cat drill automation technologies are laid out in a building block approach to allow mines to enter at different levels depending on specific site needs. The building block approach also enables upgrading the level of automation in the field as mine needs change.

The journey typically starts with the base drill auto-functions. Cat drills offer an advanced auto-controls package, which includes auto leveling/auto levelling jack retract, auto mast raise and lock/auto unlock and lower mast, plus single-pass auto drilling to include the entire drilling cycle from collaring the hole and working through changing ground conditions, to drilling down to exact depth and a retract and swab cycle – all programmable to adapt to the ground conditions and application requirements.

The next layer is outfitting the machine with Cat Terrain for drilling, which enables high precision guidance and a back-office package used to create and upload virtual drill patterns to the onboard operator. The system also sends information back to the Terrain office where software generates reports on drill productivity and utilization and tracks consumables usage.

Terrain uses high precision global navigation satellite systems to locate the machine over the hole. The system takes into account the orientation of the drill string in relation to the designed drill pattern to ensure the rig “touches” centre mass of the hole target with the bit, regardless of mast angle – out to 30° for angle drilling. It also monitors machine pitch and roll while on tracks, and it calculates trajectory of the bit when the machine is leveled. This ensures the machine can position over-the-hole perfectly without having to lower back to tracks and make minor adjustments. Terrain also controls hole depth to effectively reduce over- and under-drilling, even on rough ground.

Once Terrain is installed, the drill can be equipped with the next level of automation, Operator Mission Assist, part of Cat Command for drilling. Operator Mission Assist leverages the base machine automation functions and Terrain guidance to achieve the consistency of autonomous operation. The system enables an operator onboard the drill to select a row of holes and complete the entire drilling cycle automatically with the operator being the safety monitor. The communication network is the same as that required for Terrain for drilling.

No operator aboard

The fourth building block removes the operator from the cab of the machine and operates the drill semi-autonomously. This system has several on-board safety systems, virtual geo-fences and definable working parameters that can be set up for a work site. The drill autonomously completes a single row at a time.

This level of autonomy is intended to allow one operator to control multiple machines with a recommendation of three as optimum. The operator sets the rig up to a row of holes, launches autonomy, monitors the autonomous machines via a tablet computer, and interacts with the machines only to perform any exception management, such as shutting down a rig for refueling.

Adding a remote operator station to this semi-autonomous solution enables an operator to do all the exception handling while off the pattern, thus minimizing exposure to the elements and health and safety risks.

Semi-autonomous operation is the last building block before entering into full autonomy, which automates both drilling and tramming. The full-scale autonomous solution can vary by site since each site has different objectives. The solution requires a thorough analysis of the safety system, highly reliable network infrastructure and additional on-board hardware. There is significant change to be managed in migrating from a manned operation to a fully autonomous system. Operators will be able to monitor multiple machines from the remote operator station or from a non-line-of-sight control centre. Operators can take manual control of the machine if any exceptions occur.

Use precision, automated guidance to drill to plan for a more even, efficient blast and reduced costs downstream. And consider semi-autonomous and autonomous functions to enhance safety and improve consistency and drill utilization.

Jim Peterson is Mining Technologies Applications Specialist, Caterpillar.