Robot cutters at work in St Petersburg

Contractor ICA Construction used two Aquajet robotic hydrodemolition machines to clear surplus concrete from the top of a 120m high bridge pylon in St Petersburg, Russia.

The Petrovsky Fairway Bridge, crossing the Rover Neva, is part of the Western High-Speed Diameter (WHSD) motorway project, aiming to provide a key link between the Scandinavian Peninsula, Continental Europe, Central Russia, and the Baltic States.

Turkish-Italian construction company ICA is building a 11.57km section of the highway under a US$1.6 billion (€1.5 billion), four-year construction programme. The contract includes three major high-level bridges, together with low-level viaducts and smaller overbridges.

The Petrovsky Fairway Bridge is a 560m cable-stayed structure linking two islands. It will feature two needle-shaped towers, each 120m high. The deck will be supported by four planes of cables: the cables supporting the deck units closest to the tower will be connected to the top of the tower, with those towards the mid span connected at a lower level.

The length of the central span is 240m, and the bridge under-clearance is 25m.

On the northern pier, ICA has used two Aquajet hydrodemolition robots to cut away surplus concrete from near the top of the pylon.

Rented robots

The robot machines were rented by Termite, a hydrodemolition specialist that is a sister company to DUS, distributor for Sweden’s Aquajet Systems AS in Finland and Russia.

Max Petrov, Development Director for DUS, said that DUS was first established in St Petersburg in 2003, and began the successful marketing of Aquajet water cutters in Russia about two years ago.

He said, “For this project we used the Aqua Spine from Aquajet which is the most effective and flexible equipment you can find in the market for this type of job.

“It is easy to build the system in the size needed by using the multi-modular Aqua Spine. The spine is made to handle the reaction force from a 700hp pump with 262L/min.

“The height of the area to be removed was 10m so we assembled the Aqua Spine in the same length. We assembled the complete system on the ground which reduced the set up time.”

The 10m high Aqua Spine mast was lifted in place and bolted onto each side of the pylon. An Aqua Cutter 410A was used as the Power Control Unit to control the Aqua spine.

Mr Petrov explained, “ICA wanted to remove the concrete without causing any damage to the inner steel structure, and needed to save the vertical rebar to spend less time on recasting.”

Termite provided the two water cutters to ICA, together with operators and service backup, on a rental basis.

“The ‘trouble’ concrete was at a height of 84.5m to 94.5m, and the full thickness that had to be removed was about 77m³,” Mr Petrov said. “We placed the power pack at the bottom of the pylon and used a 120 m long high-pressure hose to access the working area.

“The hose was fed upwards inside the pylon and then through a vent hole to the outside. Our water source was the Finnish Gulf. We used three-level filtration to prepare water for the plunger pump; the used water was fed back into the sea. A caisson wall filled with sand and crushed stone surrounds the pylon. This acted as a filtration and settling tank, so the water that was pumped back into the Gulf was almost entirely clean.”

Mr Petrov says that the advantages to ICA, along with the clean cutting of the concrete, was that there was no need to have a large gang of jackhammer operators working high up on the pylon or any need to build any platforms or scaffolding.

“This is only the sixth or seventh hydrodemolition project that has been undertaken in Russia, but the concept is rapidly gaining interest. The Petrovsky Fairway Bridge has been a very high-profile job for us, and we are convinced that the market will grow strongly for Aquajet robots within the next two to three years,” he said.