Cantilever Retaining Wall Frost Depth

[Ceinostuv]

A colleague of mine is studying for the PE exam and came across a note that reads "To prevent frost heaving, the top of the base should be below the frost line. This establishes a minimum wall height, H." in reference to cantilevered retaining wall footings. Does anyone practice this and/or have an explanation for why they would be different from other walls? We can't seem to find a source for this and have typically specified bottom of footing at frost depth (also typically dictated in the Geotech reports we receive for these projects).

Judgement-In-Training

 

[JAE]

Sounds like a mistake in the verbiage.



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[bridgebuster]

The NYSDOT standard is to place the bottom of the footing at the frost depth.

 

[BAretired]

Frost penetrates deeper when the wall is not adjacent to a heated space, so frost depth outside the wall of a heated building will be shallower than a retaining wall in an open field. Another factor would be depth of snow, so if the retaining wall is adjacent to a road or sidewalk which will be cleared of snow in winter months, the depth of frost will be substantially greater.

It is not always practical to place the bottom of footing at frost depth. In some climates, that could be eight feet or more. Sometimes insulation is used above and beyond the footing to limit frost penetration.

BA