Northbrook School District 28
I have a raised bed line in which I am having frost heave
I live just north of Chicago. I used the HDPE “ladder”
method to install
my track two winters ago. I used 1 ½ “ PVC pipe for support,
these were pounded in 12 “ about every
6 feet. Last spring I
needed to try something else as frost heave had pushed up most of the track
between a half and one inch. The track is loosely wired to the ladder and I
took the track off , lifted the ladder and placed 18” steel tent augers every 6
feet that were bolted to the ladder.
Unfortunately, I have discovered extensive frost heave again. It is not
a big deal to lift off the track, but I do not want to lift up the ladders and
I can pound it back down, but does anyone have any other
ideas I can try to keep it down? More posts set deeper? Leave it pushed up and landscape
Any ideas would be appreciated.
You need to go deeper. You may be able to stop by a local nursery and ask what is your frost depth. Then start digging down below that depth. You are currently anchoring inside the frost depth and you will continually have this problem. Anchoring about a foot or so below the frost line will stop (or at least 95% stop) the anual lifting.
Planning for tomorrow is time well spent; worrying about tomorrow is time wasted.....
I live in Kalamazoo, Mich and have similar conditions to you. When I started out I built the first part of my RR with pressure treated posts that went down about 3 foot. None of that has ever moved. When I expanded the RR I used composite deck boards held up by short pressure treated boards that were supported by pvc pipes that were driven about 1 to 1 1/2 foot into the ground. Every spring I had to push the road bed back down (as long as I did it early in the spring it went down fine). I got tired of that after a few winters and pulled the pvc pipe out at just used pressure treated 2x4's (to keep the composite decking flat) with just bricks and soil under it for support. It's been good for the past two years. I think you have to either go below the frost line or don't put anything into the ground. Part way is worse than just sitting on top of the ground.
We live in the Sierra Nevada Mountains near Truckee, CA. I use the floating system for track work on our ten year old railroad. I occasionally experience frost heave. However it’s just a matter of leveling the upheaval.
Have fun, Rob
I agree with Bob. I had a series of 4'X8' "tables" bolted end-to-end sitting on bricks and patio blocks right on the bare ground. There was always some movement due to the freeze/thaw cycle but the tables moved together and seldom presented a major alignment problem. I had a couple inches of 1/4 minus gravel and crusher fines on the tables for road bed so re-alignment was usually pretty easy.
If you want a raised roadbed but don't want the work and expense of digging below the frost-line (at least 2 feet and as deep as 3 feet in the northern states) a system of platforms sitting at grade level will probably work fine for you.
As far north as you are, I would recommend at least a 42" minimum depth to get below the frost line. I lived for many years in New Jersey, and our frost line there was 36". Once below the frost line, you should have no more MAJOR frost heave issues. I would also recommend setting your posts in pea gravel, allowing the water to drain away from your posts (hence there is little water to generate ice from).
I live in the panhandle of Florida and my problem is water. It rots everything, even pressure treated succumbs sooner or later, and usually sooner. I set my posts in pea gravel for similar reasons. As the water table goes up and down, it allows the post to dry in between soakings.