What is Frost Heave?
Frost heave is the result of pressure created from a combination of freezing temperatures and soil defrosting. The fluctuating freezing and thawing conditions heave, or lift, the soil, which is often characterized by deep cracking of the soil. Plants may be uprooted from the ground as well. For many gardeners, this can become a major issue, as entire crops can be lost or damaged. Plants can quickly dry out and die once their roots have become exposed to cold temperatures. This heaving of the soil can also cause structural damage, in the form of cracks, on roadways, buildings and foundations. This damage can range from minor to major depending on location, weather conditions and soil structure.
While frost heave usually occurs in early spring, it can happen during late fall as well. This is when seasonal temperatures fluctuate most. Frost heaves are favorable whenever there is an abundance of cold air and soil moisture. Soil freezing results from this cold air, soil moisture combination. As it sinks to the ground, cold air causes water within the soil to freeze. Any additional moisture, such as that from soil defrosting, is drawn upward, freezing as well. When water freezes, it expands, creating pressure—both upward and downward. It is this pressure which causes frost heave to occur. Heaves are also more likely to happen in moisture-retaining soils such as loam, silt and clay. Well-draining soil, like that of coarse sand, rarely if ever suffers from frost heaving issues.
Although frost heave cannot be completely eradicated, as it is simply an act of nature, it can be prevented. Most heaving problems begin in low-lying areas of the landscape. Dips or depressions in the ground hold water. With the right soil and freezing temperatures, frost heave is inevitable. Therefore, it often helps to rake or smooth out these areas in order to minimize frost heaving threats. Soil moisture can also be alleviated by amending the soil with compost. Not only will this improve drainage issues, but it can also help with soil structure. Well-draining soil also warms up faster, further lessening the occurrence of frost heave. Another way to warm the soil is by applying mulch where suitable. Mulch helps insulate the soil by regulating temperature fluctuations and reducing frost penetration.
Does anyone know if there is a way to engineer roads and foundations to minimize the effect of frost heaves? I would think this would be a good topic for a graduate engineer to research. I have come across unknown frost heaves that have caused me to lose traction and spin off the roads. I am sure that I am not the only one that this has happened to. There has to be something better than those frost heave road signs that the state installs after the fact.
@valleyfiah- I grew up in Maine and still have family back east so I know exactly what you are talking about. The New England winters are a foundation contractor's dream. I can remember driving to work and there would be new frost heaves that were not there the day before. I think this is why these states have so many dirt roads. Dirt roads are so much easier to maintain than asphalt.
Now I live in the desert southwest where there is rarely a pothole. I forget what frost heaves and washboards are until I fly back east in the spring. All I can say is I am glad that I only have to put rental cars through that type of torture. Now I can buy one set of tires every three years, My vehicle does not need to be "winterized", and my repair bills are less than half what they were.
Unbelievably, frost heaves can pop up in the middle of winter, and can damage everything from roads and sidewalks to foundations and slabs. I used to live in Vermont and frost heaves were simply an unpleasant fact. Almost every January, we would have a mid-winter thaw that would melt and freeze the snow and ice. On years when the thaw was significant and there was a lot of snowfall, huge frost heaves would pop up.
My family actually had to repair the foundation of our barn because of frost heaves. A series of thaw and freeze cycles caused the ground to become saturated next to the bottom floor foundation wall. The saturated ground expanded when it froze, causing the wall to buckle and the foundation to crack near the edges.
The barn was over 100 years old, so it was likely from decades of freeze thaw cycles, but the repairs were very costly. If you tour almost any old farmhouse in the state, you will notice that none of them are plum square. Walls bow and wave, floors slant and tilt, and foundations eventually crumble. This happens regardless of how deep the foundation is poured because ground in that state is constantly moving.
This article presents a lively, informative look at frost heave. I had always wondered where those cracks in my back yard came from, and now I know.
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