InfraStructures - October 2009 - Lightweight Aqua Cutter Proves the Solution for German Lock

Lightweight Aqua Cutter Proves the Solution for German Lock

John Hooper, Joem Promotions Ltd
on behalf of Aquajet Systems AB
Special Collaboration

As part of Germany’s WSV and the Bundersministerium’s strategy to upgrade its locks on the River Neckar, hydrodemolition techniques are being employed at the Guttenbach lock where weight loadings are critical to prevent badly cracked lock walls from collapsing.

Hydrodemolition techniques using an Aqua cutter HD RA system with a robot arm from Sweden’s Aquajet Systems and weighing just 1700 kg, was chosen to remove poor quality and cracked concrete on the Guttenbach Lock.

Located on Germany’s River Neckar, the twin Guttenbach Locks were first built in 1939 with a second lock being added in 1955.

The middle wall separating both locks and also built in 1939 is just 1,2 m wide. With excessive cracking on both sides of the lock walls, weight loadings was a critical factor in determining the method of removing the concrete slab across the full 1,2 m width.

Hydrodemolition specialist Luckei Betonfrästechnik based in Bendorf, Germany, was awarded the contract for the concrete removal; opting to use its Aqua cutter HD RA robot.
Luckei is using the Hydrodemolition robot to remove 400 mm of concrete along the full 100 m long lock wall; totalling 280 m³.

The compact and versatile HD Robot Arm is proving ideal for working on the 1,2 m wide strip. It features Aquajet’s improved EDS cutting head which keeps the set distance from the nozzle to the surface independent of the selected lance angle: optimizing the removal rate and saving energy. The system also has no electric cables or sensors at the front, eliminating the risk of malfunction due to moisture.

All movements are hydraulically maneuvred by remote control, a safe distance from the unit. No manual adjustments or use of tools is required to position the robot arm.

Use of hydrodemolition techniques ensures no rebar damage, minimized risk of good concrete removal, eliminates dust and crystalline silica pollution and leaves a superior bonding surface. It is also substantially faster than mechanical removing methods and is also considerably less labor intensive.

Together with the robot, Luckei is operating a high pressure Power Pack with the capacity of 250 l/min of water at 1000 bar pressure, water is taken from the river and filtered to ensure performance is not affected by dirty water.
After use, the water is again filtered and returned to the river.

A temporary gate barrage has been placed across the upstream end of the lock closest to the river bank and water pumped out to provide a dry lock for Luckei to prepare the 9,50 m wall.

Luckei will then use hydrodemolition techniques for the severely cracked walls and is considering the use of Aquajet’s recently introduced hybrid robot offering an extended vertical cutting reach of 9 m.

Once reconcreted and additional strengthening completed with the installation of 20 m deep prestressed anchors along both sides of the lock, new gates will be installed for the lock to resume normal duties.

The River Neckar is 367 km long and forms a major tributary to the River Rhine which it joins at Mannheim discharging an average 145 m³/s of water into the Rhine; making it the fourth largest tributary and Germany’s 10th largest river.
It is navigable for cargo ships up to the river port of Plochingen, some 200 km upstream from Mannheim and features 27 locks dropping the river from 247,32 m to 86,50 m.

With barge traffic using the Guttenbach Lock every 10 – 15 min between 7am – 10pm, plans are underway to increase the length of the lock from 100 m to 130 m in readiness for the new generation of longer barges.

Main contractor for the Guttenbach Lock project is Echterhoff GmbH & Co Kg and consulting engineer is Glass Bauuternehmung GmbH.