Soils

Frost heave occurs when ice forms beneath the surface in below-freezing temperatures. The ice grows in the direction of heat loss (vertically toward the surface) starting at the freezing front or boundary in the soil. A supply of water is required for the ice to form and grow.

When the ice has grown enough to counter the overlying weight of soil, it moves the soil, heaving it upward and causing a bulge at the surface. The heave movement can be fractions of an inch and undetectable to drivers to several inches, causing a large bump.

Settlement occurs when underlying soils compact, creating a depression.

Swelling soils occurs when certain soils expand or react with water. They expand in volume, creating large forces in the soil. The soil bulges upward and creates a wavy or bumpy surface.