For as long as hard rock underground mining has been practiced, ground support has been a challenge. Without adequate ground support, mining operations can become risky, as there is an increased risk of a rock fall or collapse, endangering the lives of miners and seriously disrupting mining operations.
Over the years, a variety of methods have been developed to achieve rock reinforcement and area ground support. One of the most cost effective and efficient of these is the use of cable bolts (sometimes also called long tendons).
The use of grouted cables was originally introduced in mining to reinforce the backs of cut and fill stopes. Over time, though, the technology and materials used have improved and cable bolts are now used in a variety of applications.
Different types of cable bolts and installation methods can be used, as dictated by the conditions; for example, tensioned or untensioned cable that is installed ungrouted, partially grouted or fully grouted.
Cable bolts can be manufactured from different types of cable; for example:
- Indented cable
- Plain cable
- Plain cable with one or more bulbs (birdcages)
Some of the advantages of cable bolts are:
- Very cost-effective solution
- Can be easily installed in various lengths, typically 10 – 25m. In most cases, cable bolts are substantially longer than standard rock bolts or rebar solutions
- Can be installed in very narrow areas
- High resistance to corrosion (when in a permanent installation)
- Very high load-bearing capacity under a variety of different conditions
High-tech cable bolts, called SMART Cable Bolts, now also exist and are becoming prevalent in mining. A SMART Cable Bolt is created by fitting a miniature electronic extensometer inside a regular cable bolt, creating a device that can both provide ground support within a bolt pattern and relay data about the extent of ground movement in the area.
Overall, cable bolts provide a simple, competent, durable, cost-effective and, now high-tech monitoring solution for many ground support applications within hard rock underground mines.
