Frost susceptibility of pile supported foundations

[71corvette]

Hi All,

Does anyone have any thoughts on the frost susceptibility of pile supported foundations? Specifically, I'm dealing with an H-pile supported bridge abutment. Our state agency states that the depth of cover for frost protection shall be applied to both spread footings as well as pile supported footings but it seems pile foundations should not be all that prone to frost action.

Any thoughts, opinions or references will be greatly appreciated.

Thanks,
Tim

 

[lkjh345]

Tinytim:

We do a considerable number of pile supported buildings.
We always set the bottom of our exterior pile caps and connecting grade beams below frost depth. We do not want frost below the caps/beams to heave the foundations upwards.

Frost heave is a difficult force to control. IMHO, it is a good idea not to give it a surface to work against. It can lead to nothing but problems.

 

[msquared48]

I assume your pile are placed so the tips are below the frost line here.

Logically thinking here, discounting the weight of the pile and any dead load the pile may support, if frost heave were to occur on a pile, it would have to develop enough friction on the side of the pile to lift the pile, over-riding any side friction below the frost line. So, if the uplift force above the frost line is greater than the resisting frictional force below the frostline, plus the pile weight and supporting dead load, the pile will lift. Otherwise, no.

Mike McCann
McCann Engineering

 

[shin25]

More over, if the ratio between the live load for the bridge and the uplift for the frost action is quite large, there may be possibilty of reversal of pile skin friction. This may not be very good thing for pile capacity.