Frost Protection for Retaining Wall Foundation. 3

[BigBakwas77]

I am designing a reversed-L shaped retaining wall. (Cannot have a heel due to boundary restriction and retained earth being higher on neighbor side) If the wall height is less than 1.0m and providing 0.9 ~ 1.0m long 50mm thick rigid insulation, would it be OK to provide base around 200mm below grade?

 

[BridgeSmith]

What is the frost penetration depth for your locality?

 

[aeoliantexan]

There is a manual for designing airfield pavements on frost-susceptible soils using rigid insulation, but I can't lay my hands on it. Perhaps FAA or USAF or CRREL.

In the Midwest where maximum frost penetration was 4 to 5 feet, I used 2 inches of rigid Styrofoam insulation under critical sidewalks and pavements and had little to no movement. I also used it behind the walls where the backfill was frost-susceptible.

 

[BigBakwas77]

HotRod10 It is 4'-0".

 

[BridgeSmith]

I don't know how much of an effect the insulation will have, but a foot or so of material under the footing that is not frost susceptible (granular base) should mitigate any frost heave from the native material below.

 

[bridgebuster]

I would with HotRod10. The attached may be of some help. Also, Google "Penner, frost heave". He did a lot of research on the subject.

 

[bridgebuster]

here's another

 

[bridgebuster]

here's one by Penner

 

[oldestguy]

It depends on some factors.
Is the ground frost susceptible? If high silt content, yes. If relatively low frost heave potential, why worry?
What is this for? If a simple wall not carrying any building or fancy stuff? then no need to go to "frost depth" and let it move some.
As it is as with your diagram, that wall is a heat sink and will carry heat out and temp below the footing gets cold. Think about insulation under the footing that can take some load without compressing much.

 

[BigBakwas77]

Thank you all for your inputs, especially bridgebuster for your links. oldestguy- I believe the soil content is silt-sand, more sand. The retaining wall will be carrying a boundary fence on top and not part of the building. Hence not part of any heated area. In worst case scenario, it will retain around 30" of earth above base on higher side. I wanted the client to go 4'-0" below grade on lower side but he thinks it is an overkill- to which I partially agree.

 

[oldestguy]

I'd go with a wall no more than 2 feet down and insulation under it.