Title Image Source: Perseverance Drilling
Cable bolts installed underground cover wide span excavations or areas that require additional support due to potential rock movement and fall out. They are a system that is used in conjunction with traditional bolt and mesh systems for underground mining. The installation of cable bolts (cables) is often out of the mining cycle, in a second pass within the area. They also can cause long delays if not scheduled correctly into the mining sequence. Delays can also be created due to the multiple pass installation process that is commonplace in Australia.
The traditional method of installation involves a drill rig creating the cable holes, a service crew team and elevated platform installing the cables and grout (think a thick, pumpable cement mix). Then once the grout has cured (24-72 hours), the cables can be plated and tensioned by a second pass from the service crew. It is quite clearly a multiple staged process that has inherent dangers within the process including working at height, extensive manual handling, and potential exposure to cement.
Could underground mines look to transition to a more mechanised install for cable bolts? Improving safety outcomes for their mining crew, but also improving the speed at which cables are installed. I have compiled below a list of some of the new to market specific cable installation auxiliary rigs that could potentially be explored for underground mining projects.
Epiroc CableTec M
This machine allows the operator to use twin booms just like a jumbo. Instead,one boom drills the cable hole (up to a depth of 20) whilst the other boom can install grout and insert the cable via its specially designed tooling. This system totally removes personnel from repetitive physical labour and cement dust exposure. This is controlled by a central computer interface which delivers amazing QAQC on each bolt installed, including grout mixture feedback. Furthermore, it reduces cable install time by completing two parts of the three step process at once.
MacLean CB3 Cable Bolter
The Canadian based underground specialist delivers a fit for purpose rig specifically for safe and fast cable install. Utilising a purpose-built working platform with ergonomically designed accessories, the operator can install and grout cables with ease. All the consumables required are easily stored on the rig and feed into the drilled hole with no limitation on cable length or grout amount delivered.
Sandvik DS422i Cable Bolter
Sandvik, who have been at the forefront of this space so far within Australia, have created a rig that can deliver both drilling and cable/grout install in one pass. It is controlled from a computerised cabin with multiple controls allowing the operator to bore, inject grout and then install cable strand for curing all with one single boom. The rig looks more like a long hole rig with its rotary drill steel carrier but is noticeably different with the flexible grout pump system and large cable reel on the rear of the rig.
Summary
These machines deliver significant improvements on the historic cable install process, which is potentially hazardous, time consuming and lacks quality control measures. The reason that these haven’t made more of a footprint within the industry would be down to utilisation rates depending on site requirements. Some projects may not require a consistent, streamlined rig working 365 a year on cable bolt install, so therefore this may seem at face value an expensive solution. However, in review over the life of the machine the cost benefit analysis in improved installation times, reduced delays to other parts of the mining cycle and better working conditions for miners, could well make a cable bolt machine a smart investment for an underground mine.
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