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Ground freezing

This technique involves freezing of the groundwater. The principle is to abstract heat from the soil until the groundwater is frozen.

The following effects occur:

- water impermeability from the frozen soil

- increased strength of the frozen soil.

Ground freezing can be used in almost any type of soil, provided that the soil deposit contains sufficient water (at least 10%). The soil is frozen by insertion of lances, which can be pre-installed at the outer edge of a concrete structure or applied by means of drilling. Through the lances liquid nitrogen at 196 degrees Celsius or another fluid with a very low freezing point is pumped, causing the surrounding water to freeze. The whole process is monitored using sensors and control technology.

Application

  • Ground freezing can be used for the construction of transverse connections between for instance 2 tunneltubes or joint transitions.
  • Cable or pipeline opening that must be temporarily closed off, such as the lead-through of a large-diameter pipeline in sheet piling where no bearing may occur later on.
  • Sealing leaks (if groundwater flow is limited)
  • Applicability in poorly permeable soil where injection methods are not as suitable.
  • As emergency control measure, but can also be included in the design as alternative for jet grouting and injection.
  • Working in densely built-up areas.
  • Working with limited clearance or poor accessibility.
  • Where no foreign substance foreign to the environment may be left in the soil after the structure is finished.
  • Soil deposit may thaw, only freezing lances remain behind (can also be removed if necessary)
  • Application of ground freezing as supporting measure in polluted soil. Because no soil is removed using this technique, no increased removal/cleaning costs. In addition to impermeability to water, the frozen soil also has constructive properties.
  • Projects with high risks due to water-permeability such as transverse connections in drilled tunnels.

Ambient factors

  • Can be applied in confined spaces.
  • Low vibrations and low noise.
  • Space utilisation can be easily organised.
  • The drillings can be installed at an inclination.
  • Drilling against water pressure possible.
  • All types of soil containing at least 10% water.

Pros and Cons

  • A low-vibration and low-noise method that can be applied in any type of soil.
  • Flexible due to short preparation time, short freezing time with nitrogen.
  • Reliable and impermeable to water.
  • Environmentally friendly.
  • Optically expensive method, but often good price-quality ratio if correct risk weighing factors are applied. 
  • Time-dependent method.

Applicated

 

Name of project

Client

Amsterdam, ground freezing new entrance Van Gogh Museum

Bouwbedrijf Van der Spek bv

Amsterdam, Freezing diaphragm wall transition Noord-Zuid subwayline

Max Bögl Nederland

Rotterdam, Cross connections Statentunnel

Arge VST

Amsterdam, Cross Connections 3 caissons Noord-Zuid subwayline

Heijmans

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