Frost stroke

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Cross-section of a ground with a frost lift of 15 centimeters, below a large ice lens made of kammeis (1.), above it, frozen ground with further segregation ice in the form of smaller ice lenses (2.), above the thawed ground (3.). Taken in Spring in Norwich , Vermont, USA .

Frost lift (also frost lift ) refers to the lifting of the subsoil by ice formation when the ground is frozen in a ground susceptible to frost. The nine percent increase in volume of freezing water is not, as is often wrongly assumed, the main cause. The decisive factor for frost heave is rather that by thermodynamic processes associated with capillary effects , pore water of the soil is displaced toward the freezing front - ie generally up - and collects in a frozen state, mostly in the form of ice lenses or needle ice . Stephen Taber (1882–1963), director of the Geological Institute at the University of South Carolina , has shown that it is not the increase in volume of freezing water that is decisive for this effect . He has devoted himself to this phenomenon since the late 1920s and was able to prove that frost stroke also occurs in soil soaked with benzene, i.e. by means of a substance whose volume decreases when it freezes.

If the freezing front does not spread parallel to the surface of the ground, this effect can also act laterally, which is also referred to as a burst of frost . Ice that forms in the ground during frostbite that exceeds the pore volume is known as segregation ice . Through repeated freezing and thawing, Frosthub can cause larger objects in the ground, such as stones, to be carried to the surface of the ground. This effect is called freezing .

Frost lift is favored by a high groundwater level , a low load, a slow freezing rate and the soil's susceptibility to frost. Soils susceptible to frost are typically fine-pored and have high permeability .

literature

  • Hugh M. French: The Periglacial Environment. 3rd edition, Wiley-Verlag, Chichester 2007, ISBN 0-470-86588-1 .
  • Albert L. Washburn: Geocryology. Edward Arnold Publishers, London 1979, ISBN 0-7131-6119-1 .

Web links

Individual evidence

  1. ^ Alan W. Rempel: Frost. In: Vijay P. Singh, Pratap Singh, Umesh K. Haritashya (Eds.): Encyclopedia of Snow, Ice and Glaciers. Springer, Dordrecht 2011, pp. 303-306, ISBN 978-90-481-2641-5
  2. ↑ Ulrich Smoltczyk: Grundbau-Taschenbuch, Part 2: Geotechnical procedures. Ernst & Sohn, Berlin 2001, page 154 f., ISBN 3-433-01446-9 ( Google books )