Geotextile permittivity and permeability

[kar108]

I have a spec requiring a geotextile with a permeability of 0.1 cm/sec using ASTM D4491. I am looking at using a 0.491 cm thick geotextile with a permittivity of 0.7 sec(^-1). Calculating the hydraulic conductivity as (permittivity)*(thickness), I get k=0.293cm/sec. The data sheet lists the Water Flow Rate as 50gpm/ft^2. When I convert that to a metric velocity, I get 3.39cm/sec. Which is the correct value for the permeability?

 

[ishvaaag]

Since you have dimensionally correct formulations, the best option is to ask the maker of the table. The only (and unlikely) explanation that comes to my mind is that due to the presence of the joints the flow may jump that order of magnitude... but I think they should have that effect filtered out to more controllable proportion.

 

[fattdad]

I'd have to see the data sheet to comment. It seems to me that a data sheet that lists flow rate must also tabulate the assumed flow gradient.

According to your formula (which I agree), permeability would be 0.7*0.491=0.344 cm/sec. Not sure how you got 0.293 cm/sec. I do see how you got to the 3.39 cm/sec, but I doubt you can just convert. . .

f-d

¡papá gordo ain’t no madre flaca!