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Terrain leveler chops rocks and costs

Mar-2011

A 113-tonne Vermeer T1255 terrain leveler has helped a contractor build new spillways and dramatically cut the time required to detail excavate the spillway floor at the Keepit Dam, 56km west of Tamworth and 39km northeast of Gunnedah on the Namoi River.

Dave Thompson, the managing director of Trenching Systems Australia (TSA), which owns the T1255, said using the terrain leveler also meant significant cost savings for the contractor and the dam owner.

The Keepit Dam has a storage capacity of 425,510 megalitres, equal to the size of Sydney Harbour. The NSW State Water Corporation is overseeing a $146 million project to expand its size to ensure adequate flood protection for downstream residents and properties.

Simon Flannery, the contractor’s senior project engineer, Keepit Dam Upgrade, said the current $38 million project involved building two new spillways to improve dam safety and avoid main dam failure in an extreme flood event. The spillway project is due for completion in August 2011. A second stage will include raising the dam wall.

One spillway’s foundation was a mixture of clay and shale, which presented no problems, but the second 220m long spillway required removing very hard rock, up to 150MPa. The traditional methodology is to drill and blast the rock to foundation level, risking overblasting, which is expensive to repair with “dental” concrete.

Final detail excavation is usually done with excavators and jackhammers, because blasting cannot achieve the precision required. “With a 6500m2 area required for the spillway, it would have taken three or four weeks to get to the specific floor level we needed,” Simon Flannery said.

The T1255 Commander terrain leveler was untested in such an environment, as the machine is commonly used in surface mining. A precision construction project like Keepit Dam was novel.

“It was a bit of a gamble, but we knew if it worked it would save us weeks of heartbreak with excavators,” Simon said.

The construction team called Vermeer’s national mining services manager Craig Batten and TSA’s Dave Thompson on-site to assess the project. Both knew the T1255 was up to the task.

“The project manager and project engineer were very forward thinking and proactive. They analysed it carefully,” Dave said.

Their thinking paid off. The T1255 took only 58 hours to complete the job, profiling the spillway floor down to the exact level required. It chewed through 100mm of compacted gravel, spread across the floor surface to give the machine a stable base to work from, then through 300mm of solid rock.

“The terrain leveler is impressive to see in action,” Simon said. “It’s very aggressive.”

Dave Thompson said the T1255, powered by a 448kW Caterpillar engine, moved 3000m3 of hard meta-sandstone and metaconglomerate rock at the dam site. “She chews rock up and spits it out nicely.”

The machine achieved “a perfect result”. Dave said the floor surface was left smooth – “like a billiard table”, ready for TSA to simply “hose it off, broom it and pour concrete on it”.

Unlike the inconsistency of blasted rock particles, the T1255 creates a uniform-sized, reusable product, so a crushing plant is no longer needed on-site.

The terrain leveler’s top-down cutting produces larger product size with less fines, or more usable product. It allows more horsepower to go towards cutting the rock and less into moving the tractor.

The terrain leveler’s drum tilt system allows the machine to control grade in both lateral and longitudinal directions in a single pass, using a laser or GPS for grade control.

Simon Flannery said the T1255 had proved it had a role in the civil construction industry.

Craig Batten agreed. “We’re receiving inquiries from around the country, not only from mine and quarry sites, but from a large number of civil projects. There are numerous road, rail and construction projects the terrain leveler can sink its teeth into.”

Dave Thompson is so pleased with the machine’s success, he is planning to add another one to TSA’s fleet. Business has grown exponentially since he bought the terrain leveler in May 2010. “It’s about being imaginative with potential uses, not just traditional surface mining,” he said.

“There’s plenty of work available. It’s a matter of convincing clients of the cost savings.”

Mobilisation to site is “quite a task”, given the terrain leveler’s massive size and weight. It took three days to transport it on a lowloader from Melbourne to Tamworth for the Keepit Dam project. But according to Dave Thompson, the savings are there for clients prepared to “think outside the square” and visualise the T1255’s varied applications.

Dave, who also owns a pipe company, Polymer Welding Services, bought TSA six years ago, when it had two trenchers and two trucks. He has since expanded the fleet to 13 trenchers and the company’s assets are valued at about $15 million.

He is keen to stick with the Vermeer brand, saying the repair and maintenance network around the nation is excellent.•