Permeability of various gravels 2

[ngnear]

I need information on the permeability/porosity of various gravel sizes. Specifically, I want to know the vertical flow rate (GPM or cfs) through various thicknesses of various sizes of gravel under various heads. This info is needed for proper design of a "french drain" system or an infiltration basin. Can anyone point to a good source of (fairly extensive) data?
I've searched Google and found many sites, but none with the specific info I need. Thanks for any help.

 

[Dubliner]

Dear ngnear

The porosity and permeability of your gravels will vary with the sorting of the gravel sizes (generally, same size = higher porosity and better permeability).

I suggest you get hold of a copy of "Groundwater"
by Freeze & Cherry (Prentice Hall, 1979) from a local library. You will find estimates of permeability for particulate media (sand, gravel, etc), equations for flow and definitions of the parameters.

If you would like to email the data and your calculations to me in more detail I would be happy to take a look for you.

geologist@postmaster.co.uk

Regards

Adam B-Browne
Hydrogeologist
URS (Cardiff)

 

[gibfrog]

Check out the Naval Facilities Engineering command "Soil Mechanics" Design Manual 7.01, pg 7.1-139, permeability of sands and gravel mixtures, freely available as a pdf file download at

http://www.navfac.navy.mil/cheng/coi/civileng.htm

However, this page is not currently responding, so try

http://www.ece.jcu.edu.au/research/compgeo/geores.html#freebies

The printed manual is also availabe from NTIS (national technical information service)for around $75.

A few caveats.
1) I use the following equation to determine inflow - Q=K*G*A,
Q is the inflow, K is the permeability (provided by the chart), G is the hydraulic gradient or the head divided by the flow length and A is the average (or minimum) cross sectional area of the flow. You may need to calculate this for various heights. I usually use about 5 increments for a 6"-1' total drawdown. (When I am flowing to a pipe, I use the average pipe center line as the base elevation)
2) You should also check the perforated pipe inflow capacity based upon a orifice equation for the total pipe openings' area (if a pipe is involved in the franch drain - also you may want to verify the minimum flow velocity for the pipe) -
Q = C*A*(2gH)^.5
Q is the flow, C is the orifice constant (assumed to be 0.62, unless manufacturer data is availabe), g is 9.81 m/s^2 or 32.2 ft/s^2 and H is the head.
3) If fabric is involved, check to make sure that it is not the critical restriction in your flow, use the permeability supplied by the manufacturer.

 

[gibfrog]

I forgot to add - check out the national engineering handbook, Chapt 26, gradiation design of sand and gravel filters at

http://www.ftw.nrcs.usda.gov/neh26.html

they have the data that you want and a design example.

 

[Ron]

Why not just get a sample of the material you will use locally and take it to a local testing laboratory for at least a gradation. From that you can estimate several parameters, including porosity from basic weight-volume calculations. You could also get them to do a permeability test of the material.

Unless your "French Drain" is fairly exotic, there isn't much need for computation, as the goal of a french drain is to remove water faster than the surrounding soil ...sort of a "short circuit". For example, if you are putting a drain in a clayey material with a permeability in the range of 1x10^(-6), then almost any sand, gravel, or combination will get you into the 1x10^(-3), or even faster, range.

 

[mfrad]

Does anyone have data on the permeability rate of 4000 psi stone concrete measured in cm/sec for use in a containment dike against either oil spillage or caustic materials?

 

[RDK]

mfrad

I would not be worried about the porosity of the concrete as much as the porosity of any and all shrinkage , tension and thermal cracks in the concrete.

I would also be worried about the resistance of the concrete to long term chemical attack.

For caustic material containment, the only thing that I have seen is specialty coatings applied on the cured concrete. Your local dealer will have some information on the specific material requirements for your specific application. If you google search the terms concrete coating “your specific material’ you should get lots of leads.
Rick Kitson MBA P.Eng

Construction Project Management
From conception to completion

http://www.kitsonengineering.com