permeability estimate from fines content 1

[jgailla]

I am trying to come up with a rough seepage estimate for a wet detention pond in which the design normal water level is about 1.5 feet below the groundwater level.

The site is mostly clayey sand.

I used to have a correlation between fines content and permeability, but I just moved offices and can't find anything.

This is one of those things that shouldn't cause a problem but I need data to bring to the permitting agency.

Does anyone know of a rough correlation between k and fines for clayey (or silty) sands?

 

[Ron]

jgailla....Sowers has a table in his book for reasonable correlation. Das probably does as well. Mine are packed up or I'd check them for you. In general, clean sands will be in 10^-3 range, while clays will be in the 10^-7 range. Clayey sands will generally be in the 10^-5 range (+/-).

Here's the relationship given in a military publication...

http://www.usace.army.mil/publications/eng-manuals/em1110-2-1901/c-2.pdf

Check the figure on page 10.

 

[jgailla]

Thanks Ron. This is exactly what I was looking for. I had Das and Budhu, but the ranges didn't address sand-clay mixtures.

 

[BigH]

Check out Terzaghi Peck and Mesri - they report, from recollection, new correlations of material permeabilities after Kenney.

 

[NHSlide]

For clean sands one can use Hazen's equation:
k = C.(D10)^2
D10 = diameter for 10% finer
You can use an average value for C, C = 1.
If you take D10 in mm, your k value will come out as cm/s.

If you have even small amount of fines (clays/silts) this may reduce your k dramatically. So Hazen's k value may be your upper boundary since you have clayey sand.

I agree with Ron. 10^-5 cm/s is a good approximation for clayey sand. For fine sands, mixtures of sand, silt and clay I would say the range k = 10^-4 to 10^-6 cm/s.

hope this helps

 

[BigH]

NHSlide - if you check out later studies (i.e., Kenney), they are now arguing that using the D5 size is more appropriate. The Hazen's coefficient was really only for clean medium sand.