From face drilling rigs for underground development to long-hole production rigs, there's a wide range of equipment used in today's underground mines. Mines and mining contractors are looking for productive, safe and accurate machines - and many modern rigs have incorporated improvements and harnessed some of the latest technological advancements to match these needs, including automated features, drilling control systems, electric drivelines and better drill cabin ergonomics.

With miners reaching deeper underground levels, they are faced with issues related to ventilation, higher ambient temperatures, and more waste rock having to be hoisted up from the tunnels during the development stage. Controlling all of these factors could cost the companies a pretty penny.

Accordingly, more automation and emission-free solutions can help keep costs under control, while also creating a safer and better working environment for the operators.

"Mine development is generally a pure cost, as it rarely generates revenue. However, the phase is a necessity for production to be realised," explains Johannes Välivaara, product manager for underground development drills at Sandvik Mining and Rock Technology.

 "On top of this the global trends in underground mining, such as deeper underground mine operations, difficulties attracting a skilled and experienced workforce, and an increased safety focus, require both end-users and OEMs to find alternative ways to undertake mine development in the most efficient way possible."

He suggests that there are many ways to improve the quality and productivity of the existing underground development methods by looking at different ways to optimise the results in rock excavation through more precise drilling and blasting.

In a paper on ‘Automated drilling features for improving productivity and reducing costs in underground development', Välivaara writes that, in practice, this would mean:

• Reducing overbreak to reduce costs of loading and hauling, roof support, shotcreting, hoisting etc;
• Increasing pull-out per blast to improve the productivity and tunnel advance;
• Automated/teleremote-controlled drilling functions to keep up the production during shift changes and blasting hours;
• Drill planning and analyses tools combined with automatic boom movements to achieve predictable drilling results day after day;
• Spatial awareness (ie. underground 3-D scanning) to measure the quality of the drilling results for further optimisation; and
• Premium cabin ergonomics with increased visibility, reduced noise and dust to help operators to work more consistently for longer periods of time.

Enhanced features, automation

Drill rig manufacturers are getting more requests for automated features and functions for underground drilling machines. While the manual operator-assisted rig is still the go-to for many operations, OEMs are looking into boosting their rigs' capabilities.

When Epiroc (previously Atlas Copco) launched its first generation of digital RCS (Rig Control System), from the start it included digital drill plans and one/multi-hole automation capabilities for its drill rigs. Since then, the RCS has been developed further, and Epiroc has now reached the fifth generation.

Johan Jonsson, global product manager - face drilling equipment (Boomer range), at Epiroc says: "Our digital drill plans (ABC Regular) have helped our customers to actively reduce their overbreak and achieve smoother contours in their underground operations all over the world.

"Over the years we have added on options like the tunnel profiler that enables our customers to automatically scan the tunnel or mine roof and calculate overbreak or underbreak.

"We have also developed an automatic rig navigation function based on total station technology. This option enables the rig to automatically calculate its position underground, so the rig always knows where it is."

Today, almost all of Epiroc's Boomer face-drilling models can be equipped with its recently launched Dynamic Tunnelling Package. It enables the drill rig to do its own drill pattern based on the preferred CAD design of the mine or tunnel and the location in which it is navigated.

The Dynamic Tunnelling Package enables the operator to create the drill pattern directly on the screen in the drill rig instead of using predefined drill patterns from an office environment. This a function that increases the precision of the drill plans, and is always based on the planned contour in front of the drill rig and not on an expected theoretical position.

On the Epiroc Simba production drill rigs series, the manufacturer has added the possibility to remotely control the drill rigs from surface or from an underground control room. This can help its customers to drill over shift changes, in hazardous areas or during blasting.

By drilling over shift changes or blasting periods the mines can increase their productivity and achieve more drill hours and metres on the already installed fleet.

 

Sales director Witold Hnat of Polish manufacturer Mine Master says the company has witnessed progress in the development of feeder guidance systems for face-drilling, as well as on computer-aided drilling to execute and achieve the desired production drilling pattern.

Mine Master's latest rig launch, the Production Master 2.3 long-hole drill rig with a Montabert HC 112 drifter, developed in co-operation with CMAC-Thyssen Group, was designed for drilling parallel upholes and downholes, as well as fans and rings in vertical or inclined planes.

Its top-hammer system gives the possibility of drilling holes in a range of 64-165mm depending on the configuration, while the positioning system guides drilling in the required directions.

The machine offers good stability for fast tramming even in tough conditions. A bluetooth remote control panel is included for easy operation and drilling accuracy outside the operator's compartment. Direct hydraulic control is also installed inside the compartment. The rig's carousel-type rod handler has a capacity for 16 rods, plus an additional rod in the gripper and another one in the drilling string.

So far, two units of the Production Master 2.3 have been delivered to the Hindustan Zinc mining company in India, with a third unit scheduled for shipment at the beginning of April.

Sandvik's Välivaara explains that to make the most out of automated drill rig functions customers should be able to select the most appropriate level of automation for their application needs and operator skillsets.

"Autonomous drilling improves consistency and predictability for the drilling process as the manual error and corresponding deviations in productivity and cost control (e.g. equipment misuse) will be minimised," he says.

"On the other hand the productivity level becomes more stable across the operators, provided that the basic settings (e.g. drill plan, drilling sequence design, etc.) have been correctly input and the operators feel comfort to follow given plans and trust the unit in performing the actual drilling as much as possible. All the drilling-related data can be collected and verified against the given plan to confirm that the underground crew and planning team are aligned in following the predefined drill pattern."

Adapted for mining

Earlier this year Master Drilling launched its Mobile Tunnel Boring (MTB) solution at African Mining Indaba 2018. While tunnel boring machines (TBMs) are commonly used in civil and energy-related projects, the company wanted to design a system specifically for the mining sector.

"The idea to use conventional tunnel boring technology in a mining environment was conceived many years ago, where proven TBM technology could be adapted for use in a mining environment. Over a period of time, Master Drilling engineers have developed multiple concepts that would meet the requirements but further development was still necessary," Master Drilling's executive director and technical director Koos Jordaan explains.

"Recently Master Drilling partnered with a highly experienced TBM technology development company, Seli Technologies based in Italy, to assist with refinement of the concepts, all the while focussing on safety, mobility and operability.

"Seli Technologies has, by applying their expertise and in close cooperation with Master Drilling, come up with a workable concept that satisfies all the client requirements whilst meeting international safety standards."

The new machine is suited for the excavation of various types of tunnels. The MTB is capable of operating in rock conditions ranging from <100MPa to >300MPa UCS. In development sections, the MTB is capable of excavating mine access ramp and decline tunnels, conveyor tunnels and ring main level tunnels up to a diameter of 5.5m. In sub-level caving and cut and fill mining methods, the MTB is capable of excavating production and contact tunnels of 4.5m diameter.

Battery equipment

To help minimise emissions underground from diesel combustion engines, many OEMs are now turning to battery-powered options for their equipment, which also means mines aren't relying solely on ventilation systems.

"At the moment battery-driven equipment is a big trend within the industry, and our customers are looking for different ways to improve the air quality underground," notes Jonsson.

"Epiroc has a full range of battery-powered face and production drill rigs, loaders and trucks, meaning that a big portion of the activities in the tunnelling cycle can be performed with electric-powered equipment. Epiroc has full focus on extending the range of battery equipment, and more models will be launched within the very near future."

Many areas of the mining industry are facing a skills shortage, and underground drilling is no different.  Difficulties in finding skilled and experienced workforce, particularly in remote mine locations, have already had negative impacts for miners.

"A big challenge within the industry is to find people that would like to work underground and are skilled enough. Today, people are more hesitant to work underground and prefer jobs in a ‘cleaner' environment than in mining," says Jonsson.

Rig operators nowadays have to be both skilled and motivated.

Boart Longyear's team of drillers, which offers services for drilling production blastholes, slot raises, service holes and ground support holes for cable bolts, is responsible for the set-up, operation and maintenance of drills that conduct underground drilling services for various customers.

The drills they use are divided into top-hammer drills (Stopemaster, BCI 2, Stopemate, Fremar, Bar & Arm) and down-the-Hole (DTH) drills (Stopemaster conversion, Cubex 6200, Cubex Orion).

"The driller is primarily responsible for adding and removing rods on a drill string for the drill; the driller operates the machine to produce holes for the customer for various purposes, including service holes and blasting holes in order to create stopes," explains Al Portugie, field supervisor for production drilling services at Boart Longyear.

"The driller is responsible for moving the drill to new site locations, and will also conduct inspections, and clean and maintain the drill and other equipment to ensure all equipment is in optimal production condition."

As the manual operator is still needed at most operations, this also means that the drillers need an intelligently designed drilling station or cabin with easy-to-use  controls, so they are able to work comfortably and concentrate for the whole length of their shift. Everything should be adjustable according to size and preference.

"Maximised visibility through bigger windows and optimised location of the boom support structures, particularly when drilling the lifter or bolt holes, helps the operator to achieve better results.

"Noise levels are reduced through acoustic windows, careful material selections and minimisation of hydraulic hoses through the cabin, and a reduced dust level inside the cab will isolate the operator from the disturbances and safety-related concerns that are typically associated when working underground," says Välivaara.

Master Drilling's MTB was also developed with safety of personnel in mind. The machine would be manned by three personnel. Two rock support drill operators and one machine operator. The machine operator will operate the machine via remote control, controlling cutter head rotation speed, thrust cylinder position and advance rates. The remote control is also equipped with safety shutdown switches, which allow the operator to instantaneously stop machine operation from any location at the press of a button.

"The continuous boring process creates a controlled environment, allowing workers to concentrate sufficient energy through the MTB onto the rockface to fracture the rock structure, thus completely negating the risk of latent energy being distributed through the rock and affecting the stability of the surrounding rock. The MTB also installs the required rock support as it advances, thereby giving immediate safe working access to the tunnel," says Jordaan.

Overall, increased demand for improved safety and operator ergonomics will continue to set higher requirements for underground drilling equipment.