Pile Depth and Frost Heaving

[phonedesk]

Hello,

I have a lightweight structure supported by multiple H-piles, and I'm trying to quantify the frost heaving force on an H-pile. I know there's very limited research on this topic, but I was wondering if anyone knows (or knows a geotechnical engineer who knows) how to quantitatively design for such forces. The only equation I've found is Dalmatov's adfreezing equation:

F = L*h*(c-0.5*b*Tm)
where
F = frost heave force on the pile (kgf)
L = perimeter of foundation in contact with the frozen soil (cm)
h = thickness of the frozen soil layer (cm)
c and b = soil parameters (kgf/cm^2)
Tm = minimum soil or surface temperature (C)

While this is very helpful, I can't solve the equation without knowing the site-specific soil parameters 'b' and 'c'. Are they standard terms that a geotechnical report would yield? If anyone has any insight, it would be greatly appreciated!

(Also, I know that frost heave can only occur if the soil has the right porosity, water/moisture is present, and freezing temperatures occur. However, I can't use the typical "cheats" of changing the soil conditions via backfill, or using an expensive type of pile with a collar, or any other technique, as my project budget doesn't allow for it.)

 

[CarlB]

There is a lot of research on this topic.
Rule of thumb, to be safe from frost jacking, pile embedment should be 3 times the maximum frost penetration. Search the foundation forum. USACE has various cold region foundation design manuals and research.
This paper refers to Dalmatov method, as well as the USACE method (TM-5).

http://research.iarc.uaf.edu/NICOP/... conf/CD-ROM/Proceedings/PDF001189/123002.pdf

 

[phonedesk]

Thanks, CarlB. I've come across that paper before. It's interesting, but it's conclusion leaves me in a tough spot: It seems to state that (and I'm paraphrasing) "there are two approaches to designing for frost heave, and while one is more economical than the other, it doesn't always apply and is probably underestimating the force on steel piles. And the other is almost never economical." I need to work with steel H-piles, so I'm still at a loss.

I'll definitely give the foundation forum a try. Nonetheless, if you or anyone else has any more advice in this thread, please share!

 

[CarlB]

You may want to design by the "uneconomical" method, which is more of a US industry standard than the Russian method. Perhaps they were promoting their method? Better to over-predict than under-predict the heave forces.

Some other sources:

CRREL Report 88-21regarding frost heaving of H-piles:

http://acwc.sdp.sirsi.net/client/search/asset/1001202

UFC 3-130-04 document on arctic foundations, formerly Air Force manual TM-5:

https://www.wbdg.org/ccb/DOD/UFC/INACTIVE/ufc_3_130_04.pdf

 

[jayrod12]

An upper bound number that the Canadian Foundation Engineering Manual suggests is 150 kPa for adfreezing against steel. Multiple this by the surface area of the pile and the depth of frost penetration. The problem is this number becomes unmanageable fairly quickly.

 

[oldestguy]

While you got some answers here, that is fine. However double posting is not wanted since many of us look at more than one room. Check out the one other post that I know of. You do have the option to delete your posts.