Permeability of #57 stone

[ajm306]

I am hoping to use Darcy's Law to get the expected velocity of stormwater through a french drain I am designing. However I have not found a coefficient of permeability for #57 stone I am comfortable with. Someone told be .1cm/sec, but that seemed conservative. What K value have you used for this?
thanks

 

[gbam]

when in doubt test it. Can you have a local college run a test?

 

[TerryScan]

Looking through various results of google search:

http://people.engr.ncsu.edu/barlaz/lectures/13_lf1.pdf

- 1 cm/sec

http://publicworks.kingsporttn.gov/files/publicworks/3.pdf

- 10 cm/sec

 

[GeoPaveTraffic]

#57 stone should be pretty clean with little sand. I would expect a permeability of between 0.1 and 10 cm/sec. Permability will depend on how the material is placed in the trench (i.e. how much contamination is allowed), comapction, and actual gradation.

Now to the real question, why do you want to calculate velocity in a French drain? If you want to have conveyence, install a pipe. A French drain is to dry out an area not provide stormwater conveyence.

Mike Lambert

 

[TerryScan]

And of course....if the french drain is for infiltration, the conductivity of the soil beneath the drain will control.