High rise foundations

A 98 tonne Bauer BG 28 piling rig has been lifted to a height of 22 m by a telescopic crane into a former high-rise Second World War bunker in the Ruhr District city of Bochum, Germany.

While inside the bunker, the rig installed the foundation piles required for the construction of the "Exzenterhaus" - a 90 m tall office building - to be constructed on top of the listed circular high-rise bunker.

Designed by Berlin architect, Gerhard Spangenberg, the building will sit on the central island of the southern approach road to the city and is to become a new icon for Bochum.

As the former bunker has a diameter of just 15 m, the inside is too small for the mast of the drilling rig to be attached in-situ. This meant the machine had to be lifted into the bunker fully rigged apart from the counterweight, kelly bar and drilling tools.

The work carried out by the drilling rig is not extensive, but highly challenging, according to Bauer. Twelve piles, each with a diameter of 1,2 m, were drilled to a depth of 30 m. They carry most of the loads from the new building, as only a small proportion is transferred onto the old bunker and its almost 2 m thick walls.