Freezing Depth

Care to tell us where you live,type of climate,hemisphere of the earth?This stuff really helps.

In central Alberta, temperatures of -35C occur from time to time. Depth of frost penetration varies depending on the amount of natural insulation, particularly the snow cover. In open areas, frost penetrates from six to eight feet. The soil type is predominantly clay.

Fine grained soils such as silts, fine sands and clays are frost susceptible. Coarse grained soils such as coarse sands and gravels are not susceptible to frost heave.

Another consideration for frost penetration is surface traffic. If your pipes are under roadways the depth of frost can be significantly deeper than surrounding untravelled ground, and that frost will be the last to come out during thaw.

In Calgary, water services are spec'd below 3m in order to be out of the freeze. On pipe penetrations for some of the plants I've work on, the pipes are insulated and heat traced 1.2-2m below grade.

If you are replacing native backfill, clean uniform gravel is key as any silty or clay lenses in the backfill will create frost lenses that become heaves that will impact your pipe.

What kind of piping are you designing?

Thank you everybody! that was really healpful, and much appreciated!

I am using HDPE pipe, min 2m cover, and pipes are in trenches with pipe bedding, zonning and backfilling. there is specification for the materials to be used for trenching to meet common standards

Thanks alot!