Frost protection of fill

[m63]

Does anyone have any experience in protecting fill during Canadian winter from freezing using straw or wood chips.
Would a foot or so on top of the fill help?

Thaks

 

[CarlB]

I don't have specific experience with those materials but I know they have been used for that purpose. More typically straw than wood chips. Will work great if it doesn't get wet. Should reduce the frost penetration by several feet.

It is well documented that a surface layer of insulating material will reduce frost penetration. For example snow covered ground will have musch less frost penetration than an area kept clear of snow. The depth the frost will penetrate below the insulating layer depends on insulating value (thermal conductivity and thickness), initial ground temperature, and of course the air temperature over the freezing period.

 

[jheidt2543]

The choice of material for frost protection depends a lot on how big the area to be protected and for how long.

I've never seen wood chips used, but can't see why they wouldn't work. We've used straw to protect continous continous and spot footing trenches and also floor slab areas. It works fine if it stays dry and the wind doesn't blow. Clean up is always a problem, especially if there is blowing wind. Either way, the material has to be removed before backfilling.

We also used insulated blankets. They work fine and are reusable, but if they get wet or frozen they must be dried out before storage. There are also available electric mats and heating pipe systems both of which can be expensive.

Basically, we ended up protecting only the footings, it is easy and cost effective. We let the floor areas freeze. Then, once the building is enclosed, we would rent some 1,000,000 btu LP heaters and thaw the floor subgrade out. It takes about 3-4 days per foot of frost thickness.

NEVER use water to thaw out a subgrade you plan to pour concrete on!

 

[todousa]

If applicable/available pile snow on top the area. The snow will insulate the earth limiting frost penetration to 2-3 feet which can be excavated through. Also, keep in mind that any area receiving vehicular or equipment traffic will freeze deeper than the normal frost depth level.

 

[KRSServices]

Having residing in the Yukon, BC and Alberta I have a great deal of frost proection experience. An appropriate response is dependent on the application. Is the protection permanent or temporary? Is it to protect shallow services or deep utilities? What area are you looking at and what is the average (published) frost depth in that region? Lastly what kind of soils are being subjected to frost because each type has different frost behaviors. I have used techniques such as board insulation, pea gravel and extra bury to allieviate frost. What application is yors?

 

[m63]

We need to protect structural fill for the 4000 m2 building (slab on grade) during this winter and start building construction sometime in March.
We have already applied 1 foot of woodchips over the fill, hoping that would limit frost penetration to 2-3 feet
One foot of woodchips should equal two feet of soil (as an insulator)
Anyway, I would be interested to hear from anybody with more experience with this.
Thank you all for responding.