Text 3. Frost heaving

Frost heaving can damage houses, barns, sheds, roadways, concrete slabs, basically anything that is connected to the Earth in a place where the ground freezes. (___1___) The problem is, the lifting may not be equal around the structure.

Frost heaving (or a frost heave) 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 front or boundary in the soil. (___2___). 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. (___3___).

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. (___4___).

Frost heaving requires a frost-susceptible soil, a continual supply of water below (a water table) and freezing temperatures, penetrating into the soil. (___5___) Silty and loamy soil types, which contain fine particles, are examples of frost-susceptible soils.

Non-frost-susceptible soils may be too dense to promote water flow (low hydraulic conductivity) or too open in porosity to promote capillary flow. (___6___). These soils contain small amounts of fine particles and their pore sizes are too open to promote capillary flow.

Sentences to choose from:

a) Differential frost heaving can crack pavements and damage building foundations.

b) Examples include dense clays with a small pore size and therefore a low hydraulic conductivity and clean sands and gravels

c) Frost-susceptible soils are those with pore sizes between particles and particle surface area that promote capillary flow.

d) It requires a water supply to keep feeding the ice crystal growth.

e) Just as the phrase implies, the frost heaves, or lifts things up.

f) These grow with the continual addition of water from a groundwater source lower in the soil structure, below the freezing line in the soil.

Read text 4 divided into parts. Find answers to the questions which come before each of the coming passages.