Frost heave is an upward swelling of
soil due to formation of ice during freezing conditions. It occurs when
freezing temperature penetrates the soil. Consequently, moisture in soil converts
to ice and generates an upward movement in the soil.
The size of ice mass increases because
of continuous supply of moisture through capillary action. Soil weight might
restrain the influence of ice and generates ice lenses. Nonetheless, ice lenses
can move soil layer upward.
Frost heave inflects considerable damage to roads, channels, foundations and subsequently superstructures. In order to prevent the detrimental effects of frost heave, it is necessary to understand how it works and identify basic elements which lead to frost heave occurrence. After that, proper measures can be set up to prevent it.
How It Works?
As freezing temperature penetrates into the soil, it converts soil moisture to ice. When moisture at freezing area solidify, water from other parts of soil would moves toward freezing area through capillary action. This leads to the increase of ice size. Soil weight and other objects above would restrain ice size growth and consequently ice lenses are formed.
When freezing temperature further penetrates
soil, it leaves formed ice lenses behind. These ice lenses continue to growth
toward area that loses temperature which is toward soil surface
The ice lenses are capable of thrusting soil layer upward. It creates cracks in soil and cause damages to foundations and subsequently superstructures. It is reported that, when moisture converts to ice, its sizes increase by 9%.
Fine grain frost susceptible soil,
moisture that continuously supply water to ice lenses, and freezing temperature
are the basic elements of frost heave action.
When temperature declines, the ice
melts and the structure lows back to its location under its weight. When freezing
and thawing process repeats, it would severely deteriorate and possibly collapse.
of channels in freezing season.
load carrying capacity of subgrade
undulations and considerable damages to the pavement
foundations and slabs
Generally, frost heave can be
prevented by eliminating one of its basic elements which include fine grains soil,
frost temperature, and water. There are several measures which can be considered
to avoid frost heave:
of frost heave prevention systems such as hydronic heating system.
foundation such as piers below frost line.
backfill materials such as gravel around foundation so as to encourage water drainage.
- Use sleeve to avoid ice from gripping the
footing that withstand upward movement.
- For road
construction, replace fine grain frost susceptible soil with coarse granular
- Use capillary
breaker so as to prevent movement of water toward freezing front and
consequently decline frost heave influence.