VIDEO: Excavation revelation
By Chris Sleight02 July 2009
Lafarge's Whitwell quarry in Nottinghamshire, UK was opened in 1957. An unusual facility, it produces a chemically pure dolomitic limestone that is used in steel production as well as traditional aggregates from an underlying bed of harder material.
Despite the current economic downturn, Lafarge sees good long-term prospects for its rare smelting quality limestone. This helped justify the decision to extend the quarry, allowing access to some 20 years' worth of reserves in addition to the 17 years available from the existing site.
However, the new reserves on the other side of a small but important rural road, so gaining access to them building a bridge and cutting a new quarry haul road into the limestone underneath it. Being so close to a public highway meant blasting was out of the question, so Lafarge looked at mechanical excavation options.
Quarry manager Shane Tompkin took up the story. "On the quarry side we used a road planer. It took about 12 weeks, and it was getting through a full set of picks almost every pass. The machine just wasn't built for that sort of work."
After this experience, Lafarge looked around for a different solution to cut a ramp from underneath the newly constructed road bridge up into the quarry extension.
The answer came from specialist trenching contractor A.J. Gammond, which proposed the use of a Tesmec TRS1150 ‘Rock Hawg' mechanical excavator. To Mr Tompkin's clear delight, the company managed to excavate over 500 m3 of rock in just two weeks.
"We were scratching out heads about how to do the ramp, but the Rock Hawg really worked," said Mr Tompkin.
In fact the machine performed so well that he is considering using a larger versions - a 109 tonne TRS1475 for full-scale production extraction in sensitive areas. With two villages nearby, as well as the surrounding roads there is a railway tunnel running through the site, there are plenty of areas of the quarry where blasting is not an option as Mr Tompkin explained.
"We agreed on a handshake that we wouldn't go any closer to the village with blasting. We can blast up to 40 m up to the train line, so that's another area we might use the Rock Hawg, but that's seven to eight years away," he said.
When CE visited the site in July, both machines the machines, which are owned by Gammond and supplied by Tesmec's UK and Ireland dealer Westquay, were on site for trail and demonstration purposes. According to Mr Tompkin, the indications were that the TRS1475 could produce the 300 tonnes per hour he is looking for.
There could also be another big advantage with the Tesmec machines, as Mr Tompkin explained. "What we see with mechanical extraction is that you don't need a primary crusher. It (the aggregate) was a bit fine and dusty with the smaller machine (TRS 1150), but it looks coarser with the big one (TSR1475)."It is a prospect Mr Tompkin was clearly very excited about. He said that over the years various mechanical systems, such as dozers and excavator-mounted breakers, had been tried with unsatisfactory results. The Rockhawgs however show great potential.