Constant vs Falling Head Permeability
Constant vs Falling Head Permeability
(OP)
I have samples of clayey sand and clayey gravel (weathered granite) that I want to test for permeability. Which method should i do - falling or constant head?
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Constant vs Falling Head Permeability
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Constant vs Falling Head PermeabilityConstant vs Falling Head Permeability(OP)
I have samples of clayey sand and clayey gravel (weathered granite) that I want to test for permeability. Which method should i do - falling or constant head?
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RE: Constant vs Falling Head Permeability
RE: Constant vs Falling Head Permeability
RE: Constant vs Falling Head Permeability
RE: Constant vs Falling Head Permeability
My favorite tool for permeabilty testing is the triaxial cell as it allows backpressure saturation. Just not too sure how this would work for a clayey gravel sample.
If you are compacting the sample into some steel mold and then applying a pressure head, I'd likley use a falling head test for lower permeability soils.
If I had the option of performing a field test, that's what I'd consider first (i.e., Boutwell permeameters or slug tests).
Would like to know the context of your study, however. . .
f-d
¡papá gordo ain't no madre flaca!
RE: Constant vs Falling Head Permeability
RE: Constant vs Falling Head Permeability
Will the tank bottom be significantly above the water table?
I'd likely do three or four different things: Run a sieve and hydrometer and consider 1) correlation between "texture classification" (USDA soil triangle) and "perc" rate; 2) D10 or D20 correlations to hydraulic permeability (i.e., Hazen's formula); 3) Conduct a field permeability test (i.e., ala Hvorslev); 4) Conduct a standard-issue "perc" test.
Fundamentally, what you want to know is the rate that the permeant will migrate vertically downward at a gradient of 1.0. The perc test doesn't really tell you this as the hole size allows for horizontal spread of the permeant below the point of discharge. That said, it's unlilkely that the ENTIRE tank will fail at once, so a perc test may give you a basis to understand a practical migration rate.
Just some thoughts.
f-d
¡papá gordo ain't no madre flaca!
RE: Constant vs Falling Head Permeability
RE: Constant vs Falling Head Permeability
If the material is clayey, use falling head test.
RE: Constant vs Falling Head Permeability