Gravel/sand pressure?

[SAIL3]

The simplest way to present this question is to assume the following:
Typical formwork.....6in wide by 7ft tall and filled with gravel.
What is the design pressure from the gravel?.....thanks in advance for your response.

 

[KootK]

35 degrees is a common estimate of the angle of repose for gravel. With that in hand, perhaps you can treat it like you would a retaining wall?

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[dcarr82775]

I don't have the books handy, but bin pressures would be one way to go here. Using something like a Rankine earth pressure is not correct.

 

[SlideRuleEra]

For dry gravel, you can assume an equivalent liquid pressure of 24 to 26 lb / ft^2. Smaller gravel has less voids therefore the higher value. These numbers are based on traditional Rankine / Coulomb assumptions and should be conservative values. See pages 5 and 8 of "US Steel Sheet Piling Design Extracts" on this page of my website:

http://www.slideruleera.net/Steel-Piling.html

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[aggman]

I would approach this with Bin Theory. If you have Gaylords structural engineering handbook it can walk you through it. Other references are ACI 313-97 which addresses design and construction of concrete silos and stacking tubes. These all follow Jannsen theory. The hard part is going to be assuming a wall friction angle for the material against the wood, but I would probably assume something along the lines of what it would do against concrete and look at a range of numbers. With that small of a gap, the material is going to be significantly carried by vertical wall friction, so the forms will carry a lot of the vertical load.

 

[KootK]

To the extent that it's relevant, the article on stacking tubes is attached.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[XR250]

IRC uses 30 psf/ft for basement walls backfilled with gravel.

 

[SAIL3]

thanks to everyone for their responses......because of the narrow width, it was questionable wheather the Rankine/Coulomb or the bin theory would apply....