Jacking up office tower foundation

Situation

Across from Rotterdam Central Station, in the most prominent location of the Central District, the 130 meter high office tower "FIRST Rotterdam" marks the entrance to the town.

During the construction of the office tower, uneven settlement occurred caused by weight differentiation. The building is founded on vibro-combination piles on the first layer of sand (-28 meters NAP), which is better than building it on top of 60-meter piles. But this layer has less weight bearing strength than the deeper sand layer. In accordance with pre-calculations, the heavy concrete core could then sink by as much as 9 centimeters more than the rest of the building. To counteract this, jack points were fitted to the outer columns and the underlying two-storey car park was built in segments.

Challenge

Jacking up of the outer columns prevented problems caused by the uneven settlement of the building.

Solution

Underneath the lifting point of the heavy column on the northeast side of the building, 12 Holmatro hydraulic locknut cylinders were positioned, each with a capacity of 400 tonnes. When the hydraulic pump is switched on, the pressure of the cylinders slowly increases. At 149 bar, the thick column (1110 x 760 millimeters) raises slightly  until a gap appears. Jacking mechanics then remove the filler plates from underneath the jacking points and after the pressure of the cylinders has been decreased, the building lowers slightly.