Falling Head Test versus Constant Head Test
Falling Head Test versus Constant Head Test
(OP)
I have just performed a Constant Head Test and a Falling Head Test, now I am supposed to compare the result of the coefficients of permeability. I was wondering if the result for the Constant Head is supposed to nearly double that of the Falling Head Test.





RE: Falling Head Test versus Constant Head Test
More detail would be helpful.
f-d
¡papá gordo ain't no madre flaca!
RE: Falling Head Test versus Constant Head Test
Regarding your reported test results...I think they are actually very close, assuming the tests and computations were properly done.
I strongly recommend An Introduction to Measurement Theory and Experiment Design, D.C. Baird, 1962, Prentice-Hall, Inc.
A very small book, loaded with insight. This will change how you look at testing and computations.
RE: Falling Head Test versus Constant Head Test
I am not sure if this would have any effect on the test but there was a slight leak in the chamber was noticed when the vacuum was turned on, which I was told by my prof, that this would not make any difference with our outcome due to the speed of which a Falling head test is performed. Ottawa sand was used in both test which is air dryed. The same procedure for compaction of the sample was used in both test. The representaive k for the Constant head is 2.709x^10-4 and Falling Head is 1.831x10^-4.
Dry Densities:
Falling Head- 1.831
Constant Head- 1.722
RE: Falling Head Test versus Constant Head Test
RE: Falling Head Test versus Constant Head Test
If, for instance, you are applying 10 psi head pressure, that's the equivalent to 23 ft of water. If you measure 2 inches of "fall", that dims in comparison to the head applied by the pressure pump. I say this as loosing perspective in the triaxial chamber is common when there is pressure involved. Just something to consider.
Have fun with this. The best learning takes place when you are stumped. That said, I agree the two values are quite similar.
f-d
¡papá gordo ain't no madre flaca!