Ground freezing
Encyclopedia: Ground freezing
Ground freezingTemporary stabilisation and waterproofing of the subsoil
The ground freezing method is a method for the temporary stabilisation and sealing of the subsoil. It is used in particular for projects where drilling from the surface is only possible to a limited extent due to spatial or technical constraints. The method is frequently used in underground construction and tunnelling. Depending on the project requirements, it can be used to stabilise sections of the subsoil for the duration of the works and to protect them against water ingress.
The work is carried out taking into account the relevant geological, technical and project-specific conditions.
Technical brochureGround freezing method
Applications
Common uses for ground freezing include:
- Temporary sealing and/or support while building tunnels, especially for cross-cuts and junctions
- Producing and/or sealing shafts or construction pits
- Securing existing buildings (underpinning)
- Preparing the soil for undisturbed sampling, e.g. core drilling
Gruppeneinteilung und Anschluss der Gefrierköpfe an die Haupt-Soleleitung.
© PORR
Benefits / Features
- Closed-loop brine system: Ground freezing method using brine in a closed circuit
- Construction: Minimally invasive method with minimal vibrations
- Method: A method used for many years with project-specific monitoring
- Groundwater: No groundwater lowering required
- Space requirements: Minimal space required for execution
- Construction sequence: Above-ground uses can be maintained depending on the project
- Scope of application: Can also be used under special technical conditions, for example in tunnelling
- Quality assurance: Carried out in accordance with defined quality and monitoring measures
Basic facts
The success of ground freezing fundamentally depends on the boring technique used for the freeze boreholes. The freeze boreholes must be placed with maximum accuracy and the drill strings sunk with maximum impermeability. Other technical challenges include drilling under pressure from groundwater and in confined workspaces. PORR has the special boring equipment and proven drilling and preventer techniques necessary to carry out this construction task safely and economically with its own experienced specialist team.
Quality assurance
We ensure high execution quality with:
- Individually coordinated instructions
- Monitoring the boring accuracy, e.g. by means of an optical deflectometer
- Monitoring the temperature curves in temperature measuring lances inserted in the soil
- Monitoring the brine circuit parameters (e.g. system pressures, flow rates, temperatures)
- Clear processes governed by our quality management system in accordance with DIN EN ISO 9001:2015
Design variants
Two different freezing methods and refrigerants are available:
Brine freezing
- The refrigerant is a CaCl salt solution.
- Working temperatures down to -37 degrees C
- The brine circulates in a closed circuit and is treated by a freezing unit.
- High economic efficiency, which makes the brine process suitable for longer applications
Nitrogen freezing
- Ground freezing using liquid nitrogen
- Working temperatures down to -196 degrees C
- The target ground can be frozen quickly.
- Can also be used where there are rapid water currents in the groundwater
- Particularly suitable for short-term special applications, also in combination with brine freezing
