The Elbtower drops its anchor
At the beginning of May, construction workers completed the ground engineering works under the future high-rise building. The pile foundations are now completed, providing solid anchors for the future tower rooted firmly in the ground. Now the task is to prepare the construction pit for further earthworks.
The Elbtower’s base plate is to be poured as early as January next year. Then the building is ready to steadily grow upwards until it reaches its final height of 245 metres in three years. To ensure that the tower remains immovable for the coming decades, it must be firmly anchored in Hamburg’s soil. Because the subsoil at the Elbe bridges is considered difficult, geologists and engineers have carried out test drillings to a depth of more than 200 metres.
The piles have been in construction since the end of 2021 and will anchor the building in the ground underneath what will later become the base plate. The so-called pile foundations reach up to 75 metres deep into the ground. “In the past few months, the employees of the construction companies involved have done an enormous job on the construction site,” says Torben Vogelgesang, branch manager of SIGNA Real Estate in Hamburg.
The piles are solid concrete structures
It is by no means enough to simply ram a thick steel pipe into the ground, scoop out the soil and then pour in concrete. The piles are extremely solid – they reach a diameter of two metres. Steel pipes can only be used to support the walls of the borehole on the first few metres of the future piles. From a few metres down, however, a special supporting fluid ensures that the drill can go deeper and deeper without any soil slipping in. Once the deepest ground is reached, the soil is cleaned: each pile rests on more than three square metres of surface at a depth of 75 metres. Then the steel reinforcement is inserted for stabilisation and concrete is poured from the bottom to the top via a pipe.
»In the past few months, the employees of the construction companies involved have done an enormous job on the construction site.«
Elaborate preparations for the construction pit
The construction workers have placed a total of 63 pieces of these huge concrete structures in the ground over the past weeks. In addition, two test piles no more than ten metres deep will stabilise the future building.
The cold weather certainly had its advantages, because the large pile foundations are made of concrete using a special kind of cement. The so-called blast furnace cement hardly gives off any heat when it sets, which prevents cracks in the piles. It takes 56 days, almost two months, for the concrete to set.
Until then, the construction pit must be checked for leaks because the next stage is to excavate 130,000 cubic metres of earth. Only then can preparations for the base plate begin and with it the construction proper of the building.