# Frost Heave - Is it all or nothing?



## Jerry McColgan (Feb 8, 2008)

There has been a fair amount of discussion over the years regarding the effect of frost heave on posts inserted into the ground.

Here in central Arkansas[/b] I have not thought of it is a problem that I should concern myself with but I got to thinking and wondering if frost heave is something that you either have or do not have or if it may be something that may affect all areas but that requires deeper depth of posts as one moves further north.

My question is rather basic in that it is a question of whether I should give frost heave any consideration at all based on my location?

Thanks,

Jerry


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## altterrain (Jan 2, 2008)

Actually, frost heave can be worse in more moderate climates where you can get several freeze/thaw cycles during a winter. You don't get a the deep freeze to up heave posts but it can wreak havoc on your perennials and ground level track. 

-Brian


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## Dougald (Jan 2, 2008)

Frost heave is a simple mechanical action ... water in the soil freezes during cold weather and the water expands pushing the ground above it up.

Clearly the amount the ground moves is related to how cold it gets as well as the amount of water in the ground to expand. This of course is related to the soil characteristics and the amount of railfall. Sandy well drained soil in a dry climate has much less frost heave than poorly drained clays in a wetter environment. 
The traditional approach to dealing with frost heave has been to use one or all of three basic approaches
1) support anything at ground level on a substructue that is below the frost line so that the expanding water has nothing to get under and push up
2) provide significant drainage (usually crushed stone) under the structure so that the water drains off and there is limited expansion
3) make the structure stiff and strong (like rebar in concrete) so that if the ground heaves it will lift the structure and set it down in the same place undamaged

Houses in cold climates are built using #1 above and highways and sidewalks by #2. Anyone driving on those highways knows that the strategy doesnt always work.

Time has shown that if something is set in the ground but the frost line is lower, then the object will be pushed up with the soil and in spring as the soil settles, the object will not settle as far. This is what causes posts and all sorts of other things to be pushed out of the ground by the frost. Here the frost line is 42 inches. Anything built in the ground not on footings below that level will be pushed out in time. There are no exceptions. Even boulders weighing several tons are slowly being pushed to the surface by the frost.

I do not know if the light frost in Arkansas can cause a problem but I suspect that any post in the ground deep enough to hold stable is below the frost line. That same post here would need to be set to a minimum of 48 inches and 54 inches is recommended.

Regards ... Doug


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## Jerry McColgan (Feb 8, 2008)

Posted By Dougald on 26 Oct 2009 02:53 PM 


I do not know if the light frost in Arkansas can cause a problem but I suspect that any post in the ground deep enough to hold stable is below the frost line. 



Hi Doug,

Once again you have come up with very useful information.

I know that here water lines are supposed to be run below 18" (but seldom are). It is quite rare for us to have a bad winter and often our winters are free from any snow accumulation at all. This is quite a difference from when I lived in Chicago and one of the reasons why I moved south.

Since I do not have any track actually on the ground most likely if I did have a frost heave situation I would be able to rectify it by removing the top layer (plywood or whatever) and resetting the top layer somewhat lower on the 4' x 4's to allow for the increase in height. That by itself would take a major effort but if I am lucky everything would rise by the same amount and no significant changes would be necessary.

Unfortunately there is ground movement here without frost heave in that both our house and the shop (which is a steel building on a concrete floor) tend to move slightly as evidenced by cracks in the house wall and the ability of a steel door on the steel walled shop opening and closing with varying degrees of difficulty from season to season. I believe the movement is caused by varying levels of moisture in the soil.

Thanks,

Jerry


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## Spule 4 (Jan 2, 2008)

Here in TN it cycles regularly, freeze/thaw/freeze/thaw. But generally the top inch or two. Moles cause more damage honestly. The 18" is for short term freeze on waterlines. 

Ditto on the moisture as you pointed out Jerry, can tell on what doors you can open/close depending on the season. Worse here in Midddle TN (Karst) and have the sinkholes to prove it.....blech!


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## Madman (Jan 5, 2008)

I have found that posts set in concrete tend to be pushed up more so than posts set in screenings (crusher fines). The screenings let water in and out. They don't have enough solidity to allow frost to grab hold. They pack solidly around a post. They store easily. They make excellent track ballast. So who needs concrete?


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## Dennis Paulson (Jan 2, 2008)

I have alwys been amused each spring on my layout because any MODEL post , telephone pole or retaining wall that goes 3 or 6 inches into the dirt , is always pushed up and remained higher than the dirt that has returned to its normal level . 
When the layout had code 250 rail and track , the frost heave would cause the track to raise and turn and twist it , sometimes so much a locomotive could not run on it . 
And since I changed it all out and went to the LGB code 332 track , it really is not affected much if any at all , and can be operated anytime . 
Which is very important for all of the catenary poles and wires which are connected to the track itself , this really wouldn't work if the poles were just into the dirt itself , and there was frost heave .
All of this is on a foot of dirt , elevated 3 feet up from the ground , on two feet of pea gravel . So all this frost heave is actually in a foot of dirt . 
Sort of 24 scale feet of dirt above bed rock ...................ha ha ha


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## Madman (Jan 5, 2008)

Dennis,

If I understand correctly, the pea gravel is under the 12" of dirt. It would seem that the water would drain out through the pea gravel, leaving minimal frost heave if any. Although as I think about it, in a raised layout, like in a flower pot, the dirt would freeze sooner than the surrounding grade.


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## Ray Dunakin (Jan 6, 2008)

I never heard of frost heaves until my brother moved to Montana. First time I heard the term, I thought it was an abdominal ailment brought on by exposure to cold weather.


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## hawkeye2 (Jan 6, 2008)

Ray that is pretty good but frost heave is a misleading term for an ailment which brings severe pain to your anatomy slightly lower.


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