Lightning bolting - rock reinforcement deluxe
1. The challenge
“We were pretty much given a blank slate and brainstormed a wide scope of ideas. We then whittled it down to the best approaches that could give reasonable results within a reasonable time frame.”
"We started a project at the LKAB mine in Malmberget with the main objective of making the rock bolting process twice as fast as LKAB’s existing bolting systems."
2. The solution
“We partnered with resin suppliers to develop a pumpable type of resin with fast setting times and a ketchup-like consistency to prevent the resin from dripping from the bolt hole,” says Peter Bray.
In parallel to the resin work, an existing type of rock bolt – a Self Drilling Anchor, or SDA – underwent modification to allow the pumping of the resin. The SDA bolt is essentially a hollow steel tube with a drill bit welded to the end. It acts like a drill steel during installation and like a bolt when installed in the rock.
A major hurdle to overcome during the development of the pumpable resin system was finding a solution for flushing the resin mixer elements to enable repeated use of the mixers without clogging. After several trials, a simple solution was discovered that provided robust and reliable flushing while maintaining a closed system with no release of unmixed resin. Finally, all aspects of the design were working in harmony.
3. The result
“It’s very low maintenance. At the end of the shift, the operator simply turned the Boltec off and walked away. They loved the machine, and were very upset when the field test ended,” says Peter Bray.
Pumpable resin with SDA bolts has also been tested with extension drilling out to 15 meters in total bolt length with excellent results. Extension bolting further adds to the flexibility of the system, potentially replacing cable bolting in poor rock conditions.
“In some rock conditions, this machine provides the best solution available,” says Peter Bray.