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ASTM D5856 Permeability test
- Thread starter BigH
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- #3
Thanks Ron - the point is that in lab practice - we obtain coefficients of permeabiity normally, I would presume on a sample that has been "consolidated" to say a few hours if that (sand filter) and then the test is done, load added and again, short wait, and carry on with the test.
In the situation I am looking at, I am interested in the coefficient of permeabilty that would be applicable say at 1 year, 10 years, 50 years, 100 years - as we are dealing with loadings of up to 6 to 8 MPa or even higher. As one would presume, for long term loading there would be grain crushing and with time more crushing leading to creep and hence reduction of coefficient of permeability with time. Is this significant?
This is a vertical test so I am not contemplating at this time the difference in k due to vertical, kv, and horizontal, kh, variations - knowing that the surface kv will be less permeable than below in each layer.
Thanks for your comment - appreciate it.
![[cheers]](/data/assets/smilies/cheers.gif "[cheers] [cheers]")
In the situation I am looking at, I am interested in the coefficient of permeabilty that would be applicable say at 1 year, 10 years, 50 years, 100 years - as we are dealing with loadings of up to 6 to 8 MPa or even higher. As one would presume, for long term loading there would be grain crushing and with time more crushing leading to creep and hence reduction of coefficient of permeability with time. Is this significant?
This is a vertical test so I am not contemplating at this time the difference in k due to vertical, kv, and horizontal, kh, variations - knowing that the surface kv will be less permeable than below in each layer.
Thanks for your comment - appreciate it.
Hey BigH,
I think it's a precision and accuracy topic. The burette levels change during the test. The amount of change in time is read to some accuracy. If it moves slowly, you have less significant digits in that elapsed time.
To me, the bigger issue is gradient. Throttle up the gradient and you'll speed up the time. At some point it's a fools errand. So, if you place a limit on the maximum gradient during the run of the test, that'll add another aspect to the timing.
f-d
ípapß gordo ainÆt no madre flaca!
I think it's a precision and accuracy topic. The burette levels change during the test. The amount of change in time is read to some accuracy. If it moves slowly, you have less significant digits in that elapsed time.
To me, the bigger issue is gradient. Throttle up the gradient and you'll speed up the time. At some point it's a fools errand. So, if you place a limit on the maximum gradient during the run of the test, that'll add another aspect to the timing.
f-d
ípapß gordo ainÆt no madre flaca!
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- #5
Found out more details on the test - it is on a compacted sample. The issue I am trying to address is what happens to the coefficient of permeability under (1) increasing load due to raising of the dam and, (2) with time. Under the high loads, I suspect that the filter sands will crush - 2%? 5%"? x%? - thereby increasing the fines. The crushing can continue as creep with time; the k value would also change due to the change in the gradations.
As an aside - ran into an interesting paper by Srivastava and Babu:
As an aside - ran into an interesting paper by Srivastava and Babu:
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