Two steel and concrete foundation piles that had been driven through a 375mm culvert have been given the chop from nearly 70 metres away using the latest robotic cutting technology.
Lanes Group plc was called in after the 150mm piles were put through the concrete culvert during the building of a garage in the garden of a house in Irvine, Ayrshire. Lanes was commissioned to because the only other option was to demolish the garage and excavate the culvert. This would have been even more arduous, because the culvert was taking large volumes of water from nearby high ground, making contingency plans to manage the flow more complex. John Murray, Operations Manager at Lanes’ Glasgow depot, said that, even using remote access technology, it was a challenge. “The high and unpredictable flow rates meant we had to pick just the right moment to carry out the work and select a cutting method that could complete the task safely in as short as possible a time,” he said.
“The location where the piles had been accidentally driven into the culvert also meant our only safe entry point was from a manhole more than 60 metres away, a distance that compromised certain cutting systems.”
The answer was to deploy an electric-powered milling robot. Unlike hydraulic or pneumatic robotic cutting systems, there is no loss of power at longer distances from the point of entry into the pipe. The 760mm-long ProKASRO 4.0 DN 200-600 milling robot is designed to be operated in pipes with diameters from 200mm to 600mm. An operator controls the machine from a console in a van, viewing it through a video camera lit by LED lights. Its diamond milling head is more than a match for steel or concrete. Four specialist crews from Lanes, eight personnel in all, carried out the work. A jet vac crew set up and carried out the over-pumping. Two operatives controlled the robot. A CCTV drainage survey crew used a robotic camera to record and report evidence of the work, and a point lining team stood ready to line the pipe as soon as the piles had been cut out.
Simon Bull, Manager of the Lanes Sewer Rehabilitation and Lining Division, said: “Each pile took a full day to remove. It’s a highly-skilled, precision task that requires a delicate touch and a good deal of patience.
“Key factors were the toughness of the material, the limited operating space within the pipe, given the size of the piles, and the need to proceed with caution to avoid causing further damage to the pipe which might have caused its collapse, making excavation the only option.”
The jet vac tanker stationed at the next downstream manhole vacuumed pile fragments flushed down the pipe while larger and heavier fragments were removed at the same point by confined space entry. Then one-metre point liners were immediately installed – with each section double-lined to provide additional strength. A point liner, or patch liner, is a short liner, made from resin-impregnated sheets of glass-reinforced plastic (GRP) which is wrapped around a cylindrical rubber tube called a packer. The packer, along with the liner, is then moved into position in the pipe and inflated with compressed air to push the liner against the pipe wall where it is left to cure, or harden, in ambient temperature.
