Frost heaving

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Anatomy of a frost heave during spring thaw. The side of a 6-inch (15-cm) heave with the soil removed to reveal (bottom to top):
· Needle ice, which has extruded up from the freezing front through porous soil from a water table below
· Coalesced ice-rich soil, which has been subject to freeze-thaw
· Thawed soil on top.
Photograph taken 21 March 2010 in Norwich, Vermont

Frost heaving (or a frost heave) is an upwards swelling of soil during freezing conditions caused by an increasing presence of ice as it grows towards the surface, upwards from the depth in the soil where freezing temperatures have penetrated into the soil (the freezing front or freezing boundary). Ice growth requires a water supply that delivers water to the freezing front via capillary action in certain soils. The weight of overlying soil restrains vertical growth of the ice and can promote the formation of lens-shaped areas of ice within the soil. Yet the force of one or more growing ice lenses is sufficient to lift a layer of soil, as much as 30 cm or more. The soil through which water passes to feed the formation of ice lenses must be sufficiently porous to allow capillary action, yet not so porous as to break capillary continuity. Such soil is referred to as "frost susceptible". The growth of ice lenses continually consumes the rising water at the freezing front.[1][2] Differential frost heaving can crack pavements—contributing to springtime pothole formation—and damage building foundations.[3][4]

Needle ice is essentially frost heaving that occurs at the beginning of the freezing season, before the freezing front has penetrated very far into the soil and there is no soil overburden to lift as a frost heave.[5]

Mechanisms[edit]

Historical understanding of frost heaving[edit]

Ice lens formation resulting in frost heave in cold climates.

According to Beskow, Urban Hjärne (1641–1724) described frost effects in soil in 1694.[5][6][7] By 1930, Stephen Taber (1882–1963), head of the Department of Geology at the University of South Carolina (Columbia, South Carolina), had disproved the hypothesis that frost heaving results from molar volume expansion with freezing of water already present in the soil prior to the onset of subzero temperatures, i.e. with little contribution from migration of water within the soil.

Since the molar volume of water expands by about 9% as it changes phase from water to ice at its bulk freezing point, 9% would be the maximum expansion possible owing to molar volume expansion, and even then only if the ice were rigidly constrained laterally in the soil so that the entire volume expansion had to be taken up vertically. Ice is unusual among compounds because it increases in molar volume from its liquid state, water. Most compounds decrease in volume when changing phase from liquid to solid. Taber showed that the vertical displacement of soil in frost heaving can be significantly greater than that due to molar volume expansion.[1]

Taber demonstrated that liquid water flows towards the freeze line within soil. He showed that other liquids, such as benzene, which contracts when it freezes, also produce frost heave.[8] This ruled out molar volume changes as the dominant mechanism for vertical displacement of freezing soil. His experiments further demonstrated the development of ice lenses inside columns of soil that were frozen by cooling the upper surface only, thereby establishing a temperature gradient.[9][10][11]

Development of ice lenses[edit]

The dominant cause of soil displacement in frost heaving is the development of ice lenses. During frost heave, one or more soil-free ice lenses grow, and their growth displaces the soil above them. These lenses grow by the continual addition of water from a groundwater source that is lower in the soil and below the freezing line in the soil. The presence of frost-susceptible soil with a pore structure that allows capillary flow is essential to supplying water to the ice lenses as they form.

Owing to the Gibbs–Thomson effect of the confinement of liquids in pores, water in soil can remain liquid at a temperature that is below the bulk freezing point of water. Very fine pores have a very high curvature, and this results in the liquid phase being thermodynamically stable in such media at temperatures sometimes several tens of degrees below the bulk freezing point of the liquid.[12] This effect allows water to percolate through the soil towards the ice lens, allowing the lens to grow.

Another water-transport effect is the preservation of a few molecular layers of liquid water on the surface of the ice lens, and between ice and soil particles. Faraday reported in 1860 on the unfrozen layer of premelted water. [13] Ice premelts against its own vapor, and in contact with silica.[14]

Micro-scale processes[edit]

Frost heaving on the spot of brown earth without cover of plants. The effect of frost heaving is reduced on the area covered by grass.

The same intermolecular forces that cause premelting at surfaces contribute to frost heaving at the particle scale on the bottom side of the forming ice lens. When ice surrounds a fine soil particle as it premelts, the soil particle will be displaced downward towards the warm direction within the thermal gradient due to melting and refreezing of the thin film of water that surrounds the particle. The thickness of such a film is temperature dependent and is thinner on the colder side of the particle.

Water has a lower thermodynamic free energy when in bulk ice than when in the supercooled liquid state. Therefore, there is a continuous replenishment of water flowing from the warm side to the cold side of the particle, and continuous melting to re-establish the thicker film on the warm side. The particle migrates downwards toward the warmer soil in a process that Faraday called "thermal regelation."[13] This effect purifies the ice lenses as they form by repelling fine soil particles. Thus a 10-nanometer film of unfrozen water around each micrometer-sized soil particle can move it 10 micrometers/day in a thermal gradient of as low as 1°C km−1.[14] As ice lenses grow, they lift the soil above, and segregate soil particles below, while drawing water to the freezing face of the ice lens via capillary action.

Frost-susceptible soils[edit]

Partially melted and collapsed lithalsas (heaved mounds found in permafrost) have left ring-like structures on the Svalbard Archipelago

Frost heaving requires a frost-susceptible soil, a continual supply of water below (a water table) and freezing temperatures, penetrating into the soil. Frost-susceptible soils are those with pore sizes between particles and particle surface area that promote capillary flow. Silty and loamy soil types, which contain fine particles, are examples of frost-susceptible soils. Many agencies classify materials as being frost susceptible if 10 percent or more constituent particles pass through a 0.075 mm (No. 200) sieve or 3 percent or more pass through a 0.02 mm (No. 635) sieve. Chamberlain reported other, more direct methods for measuring frost susceptibility.[15]

Non-frost-susceptible soils may be too dense to promote water flow (low hydraulic conductivity) or too open in porosity to promote capillary flow. Examples include dense clays with a small pore size and therefore a low hydraulic conductivity and clean sands and gravels, which contain small amounts of fine particles and whose pore sizes are too open to promote capillary flow.[16]

Structures created by frost heaving[edit]

Palsas (heaving of organics-rich soils in discontinuous permafrost) may be found in alpine areas below Mugi Hill on Mount Kenya.

Frost heaving creates raised-soil landforms in various geometries, including circles, polygons and stripes, which may be described as palsas in soils that are rich in organic matter, such as peat, or lithalsa[17] in more mineral-rich soils.[18] The stony lithalsa (heaved mounds) found on the archipelago of Svalbard are an example. Frost heaves occur in alpine regions, even near the equator, as illustrated by palsas on Mount Kenya.[19]

In Arctic permafrost regions, a related type of ground heaving over hundreds of years can create structures, as high as 60 metres, known as pingos, which are fed by an upwelling of ground water, instead of the capillary action that feeds the growth of frost heaves.

Polygonal forms apparently caused by frost heave have been observed in near-polar regions of Mars by the Mars Orbiter Camera (MOC) aboard the Mars Global Surveyor and the HiRISE camera on the Mars Reconnaissance Orbiter. In May 2008 the Mars Phoenix lander touched down on such a polygonal frost-heave landscape and quickly discovered ice a few centimetres below the surface.

See also[edit]

References[edit]

  1. ^ a b Taber, Stephen (1929). "Frost Heaving". Journal of Geology 37 (5): 428–461. Bibcode:1929JG.....37..428T. doi:10.1086/623637. 
  2. ^ Rempel, A.W.; Wettlaufer, J.S.; Worster, M.G. (2001). "Interfacial Premelting and the Thermomolecular Force: Thermodynamic Buoyancy". Physical Review Letters 87 (8): 088501. Bibcode:2001PhRvL..87h8501R. doi:10.1103/PhysRevLett.87.088501. PMID 11497990. 
  3. ^ Transports Quebec (2007). "Québec Pavement Story". Retrieved 2010-03-21. 
  4. ^ Widianto; Heilenman, Glenn; Owen, Jerry; Fente, Javier (2009). "Foundation Design for Frost Heave". Cold Regions Engineering 2009: Cold Regions Impacts on Research, Design, and Construction: 599–608. doi:10.1061/41072(359)58 
  5. ^ a b Beskow, Gunnar; Osterberg, J. O. (Translator) (1935). "Soil Heaving and Frost Heaving with Special Application to Roads and Railroads". The Swedish Geological Society. C. No. 30 (Year Book No. 3). 
  6. ^ Hjärne, Urban (1694). Een kort Anledning till åtskillige Malm- och Bergarters, Mineraliers, Wäxters, och Jordeslags sampt flere sällsamme Tings, effterspöriande och angifwande [A brief guide to discovering and specifying various types of ores and mountains, minerals, plants, and soils, together with several unusual things] (in Swedish). Stockholm.  In the section "II. Fl. Om Jord och Landskap i gemeen" (II. About the soil and the landscape in general) of his book, Hiärne mentions the phenomenon of "earth casting" or "earth heaving", in which, after the spring thaw, large chunks of sod appear to have been ripped from the ground and tossed: "3. Om man seer uti andre Orter i Swerige / Fin-Est och Lif-land / etc. så wara stedt / som hår i Upland / och i Nårike i Wijby Sochn / Kongz Wallby / at Jorden sig med Torff och all till någre Alnars Långd och bredd har opkastat det 20 eller flere Karlar teke hint göra / och en stoor Graff effter sig lemnat." (3. Whether one sees in other places in Sweden, Finland and Iceland, etc., as has so happened in Uppland and in Närke in Viby parish, royal Vallby, that the earth itself with turf and all [in pieces] up to a few cubits long and wide has been thrown upwards which 20 or more men could not do, and a large pit is left afterwards.)
    Other early mentions of earth casting are quoted in: Sjögren, Hjalmar (1903) "Om ett "jordkast" vid Glumstorp i Värmland och om dylika företeelser beskrivna av Urban Hiärne" (On an "earth casting" at Glumstorp in Värmland and on such phenomena described by Urban Hiärne), Arkiv för matematik, astronomi och fysik, 1 : 75–99.
  7. ^ Patrick B. Black and Mark J. Hardenberg, ed.s, Special Report 91-23: Historical Perspectives in Frost Heave Research: The Early Works of S. Taber and G. Beskow (Hanover, New Hampshire: U.S. Army Corps of Engineers: Cold Regions Research & Engineering Laboratory, 1991).
  8. ^ Taber, Stephen (1930). "The mechanics of frost heaving". Journal of Geology 38 (4): 303–317. Bibcode:1930JG.....38..303T. doi:10.1086/623720. 
  9. ^ Bell, Robin E. (27 April 2008). "The role of subglacial water in ice-sheet mass balance". Nature Geoscience 1 (5802): 297–304. Bibcode:2008NatGe...1..297B. doi:10.1038/ngeo186. 
  10. ^ Murton, Julian B.; Peterson, Rorik & Ozouf, Jean-Claude (17 November 2006). "Bedrock Fracture by Ice Segregation in Cold Regions". Science 314 (5802): 1127–1129. Bibcode:2006Sci...314.1127M. doi:10.1126/science.1132127. PMID 17110573. 
  11. ^ Dash, G.,; A. W. Rempel, J. S. Wettlaufer (2006). "The physics of premelted ice and its geophysical consequences". Rev. Mod. Phys. (American Physical Society) 78 (695): 695. Bibcode:2006RvMP...78..695D. doi:10.1103/RevModPhys.78.695. 
  12. ^ John Tyndall (1858) "On some physical properties of ice," Philosophical Transactions of the Royal Society of London, 148 : 211–229. Summarized in: Tyndall, J. (1858). "On some physical properties of ice". Proceedings of the Royal Society of London 9: 76–80. doi:10.1098/rspl.1857.0011. 
  13. ^ a b Faraday, M. (1860). "Note on regelation". Proceedings of the Royal Society of London 10: 440–450. doi:10.1098/rspl.1859.0082. 
  14. ^ a b Rempel, A.W.; Wettlaufer, J.S.; Worster, M.G. (2004). "Premelting dynamics in a continuum model of frost heave". Journal of Fluid Mechanics 498: 227–244. Bibcode:2004JFM...498..227R. doi:10.1017/S0022112003006761. 
  15. ^ Chamberlain, Edwin J. (December 1981). Frost Susceptibility of Soil, Review of Index Tests. Hanover, NH: Cold Regions Research and Engineering Laboratory. ADA111752. 
  16. ^ Muench, Steve (6 November 2006). "Pavement Interactive—Frost Action". Retrieved 2010-03-24. 
  17. ^ Pissart, A.; Tilman, Sart (2002). "Palsas, lithalsas and remnants of these periglacial mounds. A progress report". Progress in Physical Geography 26 (4): 605–621. doi:10.1191/0309133302pp354ra. 
  18. ^ De Schutter, Paul (2005-12-03). "Palsas & Lithalsas". Retrieved 2010-03-10. 
  19. ^ Baker, B. H. (1967). Geology of the Mount Kenya area; degree sheet 44 N.W. quarter (with coloured map). Nairobi: Geological Survey of Kenya. 

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