June 27, 2025
Historical method, modern solution: Ground freezing for a high-rise building in Basel
A method rarely used in Switzerland is being applied in the construction of a new high-rise building in Basel: ground freezing. Where conventional techniques reach their limits, liquid nitrogen provides the necessary stability and impermeability – a traditional engineering solution that proves its worth even in complex urban environments.
Limited space – special solution
Ground freezing, a method seldom used in Switzerland, is being employed in the construction of a new high-rise building in the Basel region. This technique involves freezing the pore water in the soil, thereby stabilising and sealing the ground.
The reason for choosing this method is clear: in areas requiring a robust and watertight excavation pit, existing underground structures make it impossible to use large drilling equipment or diaphragm wall grabs. In a comparative study that included low-pressure injection and jetting (high-pressure injection), ground freezing emerged as the safest and most economical option.
This is how a wall of ice is created.
This technology, which dates back over 150 years, is being used to construct a section of an excavation pit up to 22 metres deep in a densely built-up urban area. A freezing wall is being formed in the affected zone to resist the pressure of both soil and groundwater – the latter reaching heights of up to 10 metres. The wall is created using vertical freezing lances, which are filled with liquid nitrogen at –196°C. The spread of the freezing front is monitored using temperature sensors installed at various depths and locations. The remainder of the pit is secured with an overlapping bored pile wall supported by a stiffening slab. Excavation work is well underway, and the freezing system was shut down a few days ago following the successful closure of the gap.
This is an exciting project that demonstrates how traditional construction methods can meet modern challenges. Two additional projects using the ground freezing method are currently underway at Gruner.
Many thanks to everyone involved in the success of this project, especially the team led by Dr W. Orth.
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Further information on the ground freezing technique can be found here (only available in German): Geotechnik Schweiz conference on the method
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