Insulation to Prevent Frost Heave in Pipe Rack Piles

[CANeng11]

We are having an issue with frost heave in a truck loadout piperack in Northern Alberta. The piles are steel piles that were originally driven 14ft below grade according to the drawings we have. The site has been shortening the pipe stands every spring the past few years to deal with the frost heaving and I would estimate its heaved at least a foot, probably 2.

One solution that was proposed to me was to install insulation around the piles, extending about 3 meters around the piles and at a depth of about a foot. Does anyone have any experience with this method? Or any other suggestions? We have looked at replacing the piles with screw piles, but the layout of the pipe rack makes this difficult.

 

[CarlB]

I'll respond, since I did suggest insulation in your previous post on this.
This same concept is applied in ASCE 32, for insulating below unheated buildings.
Horizontal insulation is also in road subgrade design, to reduce frost penetration into frost susceptible subgrade materials.
So yes, it's a proven method.


Depth of 1 foot works thermally, but I'd suggest a little deeper, maybe 2 feet, for physical protection and since shallow first 12" or so over insulation is difficult to compact.
Thickness-probably 4",that should prevent frost from deeper than about 2 feet below it.
3m laterally sound like more than plenty, 4 feet is probably sufficient. Rule of thum, lateral extent of insulation beyond what's being protected should be aequal to maximim frost depth minus insulation depth. So say maximum frost is 8 feet, insulation is 2 feet deep, should extend 6' laterally.

It there is a chance of fuel spills (which can disintegrate insulation), should cover it with a membrane.

 

[CANeng11]

Thanks. Do you think that jacking due to frost adhesion would also be an issue? Is there anyway to mitigate this?

 

[aeoliantexan]

I have used polystyrene board insulation under pavements and sidewalks in Iowa and Nebraska to reduce frost heave. Report No FAA-74-30, Design of Civil Airfield Pavements for Seasonal Frost and Permafrost Conditions, Written by Richard Berg at Cold Regions Research and Engineering Laboratory, has design methods for determining how much insulation is needed to allow frost penetration to only a certain depth beneath the insulation. If the soil within that depth is non-frost susceptible granular soil, the heave can be negligible. I would guess that the insulation needs to run laterally from your foundation a distance of some multiple of the frost depth. There may be a more recent publication.

What is the depth of frost penetration there?

 

[CANeng11]

Around 7 feet.