Fagyásheave

Fagyásheave is the phenomenon commonly known in English as frost heave. It refers to the upward movement of soil, aggregates, and any embedded objects caused by the freezing of pore water. The effect is most noticeable in cold climates where freeze–thaw cycles occur and can lead to surface deformation and damage to infrastructure such as roads, sidewalks, and pipelines.

The mechanism involves water within the soil migrating toward the freezing front. As temperatures drop, capillary action and pressure gradients cause unfrozen water to move toward the area where ice is forming. Within the soil, layers of ice, known as ice lenses, can develop and grow, pushing soil grains upward. Because ice has a larger volume than liquid water, this expansion contributes to heave. The magnitude of fagyásheave depends on moisture content, soil type, temperature gradients, and the continuity of freezing cycles.

Conditions that favor frost heave include saturated or nearly saturated soils, especially fine-grained sediments with strong capillary action, and repeated freezing and thawing. Moisture availability near the surface and low soil compaction also increase vulnerability. Soils with high clay content or silt are often more susceptible, though the exact behavior varies with local conditions and impurities.

Impacts and mitigation are central to civil engineering practice. Frost heave can cause road and sidewalk buckling, misalignment of pipelines, and foundation distress. Mitigation strategies include improving drainage to limit moisture reaching the frost zone, insulating the ground or using frost-protective foundations, and designing joints or ground slabs to accommodate movement. In some cases, reducing moisture supply or relocating utilities away from zones of active frost is employed.