When the water flows in the upward direction from water table to capillary fringe, it generally gets freeze when the temperature falls below freezing point and this term is referred as ‘frost heave or frost heaving‘.
In simple terms frost heaving means the contraction and expansion of soil due to freezing and thawing conditions.
Due to this the water gets converted into ice and generally its volume gets increased. The change in volume can be between 5 – 10 %. This volumetric change leads to the change of volume of soil.
This results in the lifting of small objects on the top surface of the ground. This condition is generally observed in cold regions.
As you can see in the left picture that ice lens has been started forming due to the moisture present in the soil. Later in the right picture these lens gets bigger in size as more water is rising due to the capillary action. This results in pavement heave and sometimes it also gets cracked.
What Causes Frost Heave ?
Some of the basic conditions which can encourage the formation of frost heave are mentioned below :
- Soil temperature below freezing point.
- Saturation of soil during freezing period.
- Increased permeability of soil to move water quickly through it.
Major Effects of Frost Heave
- It can seriously cause damage to pavement, house, driveways etc.
- This process is repeated yearly which can result in deterioration of concrete.
- If concrete piles are not installed deeper below, the frost line can cause lifting up of piles which can damage the above structure as well as the pile.
Also Read : Index Properties of Soil and Its Formation
Also Read : Soil Structure and Their Types
Frost Heaving Prevention
Generally frost heave can be prevented by avoiding any conditions which encourages frost heave formation. Some of the preventive measures are listed below :
- During the construction of the new building, the footing should be extended below the frost line.
- Proper water drainage methods should be applied to the foundation.
- Stabilization of soil.
- Additives such as dispersing agent can be boon for the prevention of it.
- Frost susceptible soil should be replaced with coarse grained soil.
- Providing an insulating blanket between ground surface and the water table can avoid the frost effect.
image credit : overlays.acpa.org