tiistai 6. helmikuuta 2018

Frost line

The frost line - also known as frost depth or freezing depth - is most commonly the depth to which the groundwater in soil is expected to freeze. 
The frost depth depends on the climatic conditions of an area, the heat transfer properties of the soil and adjacent materials, and on nearby heat sources. 

For example, snow cover and asphalt insulate the ground and homes can heat the ground (see also heat island).
The line varies by latitude, it is deeper closer to the poles. 
Maximum frost depth in the contiguous ranges from zero to about 2,5 m. Below that depth, the temperature varies, but is always above 0 °C.

A really great video that shows winter work and how to use machines efficiently
See and look, how easy the Case Backhoe moves in Finland (digging position) and that reasons not necessity needs (stupid) sliding boom. The 4-spoke bucket is also unnecessary, to earth constructions works. 

And fortunately, here all machines are sold frog legs, no stupid pillar feet who not enough to stabilize the machine enough soft soil

Skandinavia, to here where we live, untouched soil freezes 50-70 cm deep, without snow cover about 1 meter. If the soil are foot walking way the depth is greater (1m), and also the path or road freezing depth zero, limit is over 2m.

Alternatively, in Arctic and Antarctic locations the freezing depth is so deep that it becomes year-round permafrost, and the term "thaw depth" is used instead. Finally, in tropical regions, frost line may refer to the vertical geographic elevation below which frost does not occur.

Frost front refers to the varying position of the frost line during seasonal periods of freezing and thawing.
Building works mustbe take to frost depth, because frost many times which can damage buildings by moving their foundations. Foundations are normally built below the frost depth for this reason. 

Very typical terrain digs. In addition boulders under street and winter work, just like here. Very typical terrain digs, freezer soil, in addition boulders under street and winter work, just like here

Drink and day usewater and sewage pipes are normally buried below the frost line to prevent them from freezing. Alternatively, pipes may be insulated or actively heated using heat-tape or similar products to allow for shallower depths. 
Due to additional cost, this method is typically only used where deeper trenching is not an option due to utility conflicts, shallow bedrock, or other conditions that make deeper excavation infeasible.

There are many ways to predict frost depth including factors which relate air temperature, soil temperature and soil properties.
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. Differential frost heaving can crack road surfaces - contributing to springtime pothole formation - and damage building foundations. Frost heaves may occur in mechanically refrigerated cold-storage buildings and ice rinks.


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

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