Frost protection - void form thickness design 1

[monopoly]

Hi all, this may be old to someone but i need your input on frost heave design for my foundation.
I'm designing an unheated structural slab supported on piles. Design depth of frost penetration is 2700mm from soil report. I'm going to use Dow ethaform void form but i dont know how to calculate the thickness of void form to reduce uplift on my foundation. Let say, for frost heave uplift of 100 kPa, from soil report, if using 100mm thickness void form, what is the pressure underneath of foundation and if using 200mm thickness void form, how better i will have ???
Anyone has design guide or manual or any detail reference, it would be appreciate.
Thank you

 

[JAE]

I've seen 21 feet of frost in Nebraska....




OK....it was in a freezer warehouse where the underfloor heating system failed over 20 years.

 

[dik]

I should have noted that some foams can exert a substantial pressure... you have to realise that 8 psi is actually close to 1200 psf... and the crushing strength increases as the material is compressed...

Currently looking at using void form horizontally... I have a mine that the potash material deforms plastically over a period of time. I'm building a large sump pit and want to prevent the walls from crushing the pit walls. Planning to use void form and design the wall cantilevers for the anticipated pressures and deformation of the foam.

Dik

 

[Ron]

We have extensive frost in Florida...sometimes three or four times a year....sometimes it even covers all of the grass, not just the shaded parts.

 

[dik]

I noted in an earlier post to our CBO that we can wake up to -40 in the winter. We often have a few weeks where the temp dips to -35 or so with the occasional day of -40... January and February are often down at -30 or so for extended periods.

Dik

 

[JAE]

Ron, so frost heave for Florida is when a Floridian looks out the window in the morning and spits out his coffee and breakfast when he sees all the white on the grass?

 

[Ron]

JAE...exactly! It means you have to wear a sweater,or God forbid, a jacket.

If the temp drops below 60F, it's not good!

Sometimes I want to move back to Central Florida where it's warm.

 

[bobbybeaver]

Dik
Re sump pit. Did you mean to use the void matieral =vertically (not horizontally)?

 

[dik]

That's what I'm thinking of doing... to establish some lateral load values against the pit wall...

Dik

 

[bobbybeaver]

Perhaps the stress strain data at

http://www.beaver

plastics - DYNAFLEX, from one of the calculators
would be helpful , if you know what the wall can handle for lateral load, and you can make a guess at how much strain (soil face movement) you think you should provide for.

 

[dik]

Thanks BB... often use Frostcushion... great product.

Dik