Frost heaving can be divided into two types: surface and structural frost heaving. In the spring, gravel roads are first affected by surface frost heaving as the warmth melts the surface layer of the road but the moisture is unable to flow through the frozen road structure. This may cause the surface layer of the road to become very soft. In case of long wet periods, surface frost heaving may also occur in the summer and in the autumn.

Structural frost heaving appears as the warmth further melts the road structure. The structure and the water within begin to melt. The melting of the structure may sometimes cause great deformations in the road. At this stage, the bearing capacity of the road structure is also at its weakest, and in some cases, we need to limit the traffic on the road by imposing a weight restriction.

Read more:

• Frost heaving on the roads (Finnish Transport Infrastructure Agency)
• Weight restrictions (Finnish Transport Infrastructure Agency) in Finnish