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Frost heaving

Frost heaving

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Frost heaving results from ice forming beneath the surface of soil during freezing conditions in the atmosphere. The ice grows in the direction of heat loss (vertically toward the surface), starting at the freezing
Freezing
Freezing or solidification is a phase change in which a liquid turns into a solid when its temperature is lowered below its freezing point. The reverse process is melting....

 front or boundary in the soil. It requires a water supply to keep feeding the ice crystal growth; and the growing ice is restrained by overlying soil, which applies a load that limits its vertical growth and promotes the formation of a lens-shaped area 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
Capillary action
Capillary action, or capilarity, is the ability of a liquid to flow against gravity where liquid spontanously rise in a narrow space such as between the hair of a paint-brush, in a thin tube, or in porous material such as paper or in some non-porous material such as liquified carbon fiber, or in a...

, 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.
Differential frost heaving can crack pavements and damage building foundations
Foundation (architecture)
A foundation is the lowest and supporting layer of a structure. Foundations are generally divided into two categories: shallow foundations and deep foundations.-Shallow foundations:...

.

Needle ice
Needle ice
Needle ice is a phenomenon that occurs when the temperature of the soil is above and the surface temperature of the air is below . The subterranean liquid water is brought to the surface via capillary action, where it freezes and contributes to a growing needle-like ice column.The ice needles are...

 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.

Historical understanding of frost heaving



According to Beskow, Urban Hiäme described frost effects in soil in 1694. Taber disproved the hypothesis that frost heaving results from molar volume expansion with freezing of water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...

 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
Molar volume
The molar volume, symbol Vm, is the volume occupied by one mole of a substance at a given temperature and pressure. It is equal to the molar mass divided by the mass density...

 of water expands by about 9% as it changes phase
Phase transition
A phase transition is the transformation of a thermodynamic system from one phase or state of matter to another.A phase of a thermodynamic system and the states of matter have uniform physical properties....

 from water to ice at its bulk freezing point
Freezing Point
Freezing Point is a news journal in the People's Republic of China which has been the subject of controversy over its criticism of Communist Party officials and the sympathetic ear it lent to a Chinese historian who had criticized official history textbooks...

, 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
Ice
Ice is water frozen into the solid state. Usually ice is the phase known as ice Ih, which is the most abundant of the varying solid phases on the Earth's surface. It can appear transparent or opaque bluish-white color, depending on the presence of impurities or air inclusions...

 is unusual among compounds because it increases in molar volume from its liquid state, water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...

. Most compounds decrease in volume when changing phase
Phase (matter)
In the physical sciences, a phase is a region of space , throughout which all physical properties of a material are essentially uniform. Examples of physical properties include density, index of refraction, and chemical composition...

 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.

Taber demonstrated that liquid water flows towards the freeze line within soil. He showed that other liquids, such as benzene
Benzene
Benzene is an organic chemical compound. It is composed of 6 carbon atoms in a ring, with 1 hydrogen atom attached to each carbon atom, with the molecular formula C6H6....

, which contracts when it freezes, also produce frost heave. This ruled out molar volume changes as the dominant mechanism for vertical displacement of freezing soil. His experiments further demonstrated the development of ice lens
Ice lens
An Ice Lens or ice lenses are formed when moisture, diffused within soil or rock, accumulates in a localized zone. The ice initially accumulates within small collocated pores or pre-existing crack, and, as long as the conditions remain favorable, continues to collect in the ice layer or ice lens,...

es inside columns of soil that were frozen by cooling the upper surface only, thereby establishing a temperature gradient
Temperature gradient
A temperature gradient is a physical quantity that describes in which direction and at what rate the temperature changes the most rapidly around a particular location. The temperature gradient is a dimensional quantity expressed in units of degrees per unit length...


Development of ice lenses


The dominant cause of soil displacement in frost heaving is the development of ice lenses
Ice lens
An Ice Lens or ice lenses are formed when moisture, diffused within soil or rock, accumulates in a localized zone. The ice initially accumulates within small collocated pores or pre-existing crack, and, as long as the conditions remain favorable, continues to collect in the ice layer or ice lens,...

. During frost heave, one or more soil-free ice lenses grow, and their growth displaces the soil above them. These grow with the continual addition of water from a groundwater source lower in the soil structure, below the freezing line in the soil. The presence of frost-susceptible soil with a pore structure that promotes capillary flow
Capillary action
Capillary action, or capilarity, is the ability of a liquid to flow against gravity where liquid spontanously rise in a narrow space such as between the hair of a paint-brush, in a thin tube, or in porous material such as paper or in some non-porous material such as liquified carbon fiber, or in a...

 is essential to delivering water to the ice lenses, as they form.

Water can arrive at the forming ice lens at a temperature that is below the bulk freezing point, owing to the Gibbs-Thomson effect
Gibbs-Thomson effect
The Gibbs–Thomson effect relates surface curvature to vapor pressure and chemical potential and is a consequence of surface tension. It is named after Josiah Willard Gibbs and William Thomson, 1st Baron Kelvin. It leads to the fact that small liquid droplets The Gibbs–Thomson effect (also called...

 of confinement of liquids in pores. Very fine pores have a very high curvature
Curvature
In mathematics, curvature refers to any of a number of loosely related concepts in different areas of geometry. Intuitively, curvature is the amount by which a geometric object deviates from being flat, or straight in the case of a line, but this is defined in different ways depending on the context...

, and this results in the liquid
Liquid
Liquid is one of the three classical states of matter . Like a gas, a liquid is able to flow and take the shape of a container. Some liquids resist compression, while others can be compressed. Unlike a gas, a liquid does not disperse to fill every space of a container, and maintains a fairly...

 phase
Phase (matter)
In the physical sciences, a phase is a region of space , throughout which all physical properties of a material are essentially uniform. Examples of physical properties include density, index of refraction, and chemical composition...

 being thermodynamically stable
Thermodynamic equilibrium
In thermodynamics, a thermodynamic system is said to be in thermodynamic equilibrium when it is in thermal equilibrium, mechanical equilibrium, radiative equilibrium, and chemical equilibrium. The word equilibrium means a state of balance...

  in such media at temperatures sometimes several tens of degrees below the bulk freezing point. Another water-transport effect is the preservation of a few atomic layers of liquid water on the surface of the ice lens, and between ice and soil particles. Faraday reported on the unfrozen layer of premelted
Premelting
Premelting describes the fact that, even below its melting point , quasi-liquid films can be observed on crystalline surfaces. The thickness of the film is temperature dependent. This effect is common for all crystalline materials.Premelting shows its effects in e.g...

 water in 1860."
Ice premelts against its own vapor
Vapor
A vapor or vapour is a substance in the gas phase at a temperature lower than its critical point....

, and in contact with silica.

Micro-scale processes


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 free energy
Thermodynamic free energy
The thermodynamic free energy is the amount of work that a thermodynamic system can perform. The concept is useful in the thermodynamics of chemical or thermal processes in engineering and science. The free energy is the internal energy of a system less the amount of energy that cannot be used to...

 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." This effect purifies the ice lenses as they form by repelling fine soil particles. Thus a 10-nanometer film of unfrozen water around each micrometre
Micrometre
A micrometer , is by definition 1×10-6 of a meter .In plain English, it means one-millionth of a meter . Its unit symbol in the International System of Units is μm...

-sized soil particle can move it 10 micrometres/day in a thermal gradient of as low as 1°C km−1. 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



Frost heaving requires a frost-susceptible soil, a continual supply of water below (a water table
Water table
The water table is the level at which the submarine pressure is far from atmospheric pressure. It may be conveniently visualized as the 'surface' of the subsurface materials that are saturated with groundwater in a given vicinity. However, saturated conditions may extend above the water table as...

) 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.

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 clay
Clay
Clay is a general term including many combinations of one or more clay minerals with traces of metal oxides and organic matter. Geologic clay deposits are mostly composed of phyllosilicate minerals containing variable amounts of water trapped in the mineral structure.- Formation :Clay minerals...

s with a small pore size and therefore a low hydraulic conductivity and clean sand
Sand
Sand is a naturally occurring granular material composed of finely divided rock and mineral particles.The composition of sand is highly variable, depending on the local rock sources and conditions, but the most common constituent of sand in inland continental settings and non-tropical coastal...

s and gravel
Gravel
Gravel is composed of unconsolidated rock fragments that have a general particle size range and include size classes from granule- to boulder-sized fragments. Gravel can be sub-categorized into granule and cobble...

s, which contain small amounts of fine particles and whose pore sizes are too open to promote capillary flow.

Structures created by frost heaving



Frost heaving creates raised-soil landforms in various geometries, including circles, polygons and stripes, which may be described as palsa
Palsa
thumb|right|300px|A group of well developed palsas as seen from abovePalsas are low, often oval, frost heaves occurring in polar and subpolar climates, which contain permanently frozen ice lenses...

s in soils that are rich in organic matter, such as peat, or lithalsa in more mineral-rich soils. The stony lithalsa (heaved mounds) found on the archipelago of Svalbard
Svalbard
Svalbard is an archipelago in the Arctic, constituting the northernmost part of Norway. It is located north of mainland Europe, midway between mainland Norway and the North Pole. The group of islands range from 74° to 81° north latitude , and from 10° to 35° east longitude. Spitsbergen is the...

 are an example. Frost heaves occur in alpine regions, even near the equator
Equator
An equator is the intersection of a sphere's surface with the plane perpendicular to the sphere's axis of rotation and containing the sphere's center of mass....

, as illustrated by palsa
Palsa
thumb|right|300px|A group of well developed palsas as seen from abovePalsas are low, often oval, frost heaves occurring in polar and subpolar climates, which contain permanently frozen ice lenses...

s on Mount Kenya
Mount Kenya
Mount Kenya is the highest mountain in Kenya and the second-highest in Africa, after Kilimanjaro. The highest peaks of the mountain are Batian , Nelion and Point Lenana . Mount Kenya is located in central Kenya, just south of the equator, around north-northeast of the capital Nairobi...

.

In Arctic
Arctic
The Arctic is a region located at the northern-most part of the Earth. The Arctic consists of the Arctic Ocean and parts of Canada, Russia, Greenland, the United States, Norway, Sweden, Finland, and Iceland. The Arctic region consists of a vast, ice-covered ocean, surrounded by treeless permafrost...

 permafrost
Permafrost
In geology, permafrost, cryotic soil or permafrost soil is soil at or below the freezing point of water for two or more years. Ice is not always present, as may be in the case of nonporous bedrock, but it frequently occurs and it may be in amounts exceeding the potential hydraulic saturation of...

 regions, a related type of ground heaving over hundreds of years can create structures, as high as 60 metres, known as pingo
Pingo
A pingo, also called a hydrolaccolith, is a mound of earth-covered ice found in the Arctic and subarctic that can reach up to in height and up to in diameter. The term originated as the Inuvialuktun word for a small hill. A pingo is a periglacial landform, which is defined as a nonglacial...

s, 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
Mars Global Surveyor
The Mars Global Surveyor was a US spacecraft developed by NASA's Jet Propulsion Laboratory and launched November 1996. It began the United States's return to Mars after a 10-year absence. It completed its primary mission in January 2001 and was in its third extended mission phase when, on 2...

 and the HiRISE
HiRISE
High Resolution Imaging Science Experiment is a camera on board the Mars Reconnaissance Orbiter. The 65 kg , $40 million instrument was built under the direction of the University of Arizona's Lunar and Planetary Laboratory by Ball Aerospace & Technologies Corp....

 camera on the Mars Reconnaissance Orbiter
Mars Reconnaissance Orbiter
Mars Reconnaissance Orbiter is a NASA multipurpose spacecraft designed to conduct reconnaissance and Exploration of Mars from orbit...

. 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

  • Needle ice
    Needle ice
    Needle ice is a phenomenon that occurs when the temperature of the soil is above and the surface temperature of the air is below . The subterranean liquid water is brought to the surface via capillary action, where it freezes and contributes to a growing needle-like ice column.The ice needles are...

  • Palsa
    Palsa
    thumb|right|300px|A group of well developed palsas as seen from abovePalsas are low, often oval, frost heaves occurring in polar and subpolar climates, which contain permanently frozen ice lenses...

  • Pingo
    Pingo
    A pingo, also called a hydrolaccolith, is a mound of earth-covered ice found in the Arctic and subarctic that can reach up to in height and up to in diameter. The term originated as the Inuvialuktun word for a small hill. A pingo is a periglacial landform, which is defined as a nonglacial...

  • Lithalsa
    Lithalsa
    Lithalsa is a frost-induced raised land form in permafrost areas with mineral-rich soils, where a perennial ice lens has developed within the soil. The term sometimes also refers to palsas and pingos.-See also:* Cryoturbation* Frost heaving* Gelifluction...

  • Frost weathering
    Frost weathering
    Frost weathering is a collective name for several mechanical weathering processes induced by stresses created by the freezing of water into ice. The term serves as an umbrella term for a variety of processes such as frost shattering, frost wedging and cryofracturing...

  • Frost law
    Frost law
    Frost laws are seasonal restrictions on traffic weight limits and speeds on roadways subject to thaw weakening.In climates that experience below-freezing temperatures, damage to roads from thaw-weakening have led to many U.S...


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