Only if the permeability is homogeneous (unlikely). Horizontal permeability is often 4 to 10 times greater than vertical permeability when dealing with settlement sensitive soils (i.e., sedimentary soils).
fattdad makes the correct point - in most fine grained soils due to deposition, the horizontal permeability will always be higher. If you want to do horizontal consolidation - get a block sample and cut it to fit in the consolidation ring at 90deg. In this case you will find that the time for t95 will drastically reduce. Years ago, Lee put out a book on state of art in geotechnical (have a copy but in storage) and they had a huge chapter on 1-D and 3D consolidation.
You can test a 90-degree sample, and you will probably find that it is substantially higher than Cv of a normal sample, but how do you use that? For typical consolidation analyses, we pretend that perfect drainage (zero excess PWP boundary condition) is provided by more pervious layers above and/or below the soft clay. What is the analogous boundary condition for horizontal consolidation?
Or, is the OP referring to vertical consolidation with radial drainage to sand drains or wick drains?
dgillette, Ch - coefficient of consolidation for horizontal drainage
fattad, I agree with your point
BigH, I don't think 90-degree turned sample really measures Ch. If you think about the forces acting on this sample:
Sigma(h) - vertically (i.e. on the horizontal face)
k0.Sigma(h) - radially (i.e. on the vertical face) instead of Sigma(v).
It is really a horizontal permeability test that you should be doing at various pressures perpendicular to the horizontal, isn't it? That is what you are really looking for (and ci does correspond to ki - though applied stress does have an effect (see Conduto's book on Geotechnical Engineering Principles and Practice, eq'n 12.1).
You won't find a standard test for a laboratory determination of Ch. In the field you can determine Ch values from dissipation tests with a CPTU.
Now if you need a value for Ch it means than you have to design a vertical drain grid. Ch can vary from 1.5 to more than 10 times Cv. Usually between 5 to 10. The more the soil is layered ( with sandy layers for example, the bigger the coefficient ). You must keep in mind that you start from a Cv value which itself is questionnable !
from my point of view, I "guesstimate" the coefficient from the geological description of the borehole logs and the confidence I have in the Cv value given to me.
The most important aspect you should keep in mind is the economics behind it. Vertical drains are cheap : check both designs with Ch = 5 Cv and Ch = 10 Cv and you will see that the extra money is generally not work the risk unless you are not in a hurry ( but who isn't nowadays !
For lab test, you can refer to the method proposed in BS1377-6:1990. See the chapter "Procedure for consolidation test with drainage radially",I think it is more reliable.
For in-situ test,CPTU with dissipation test is a good and convenient way to do that.The interpretation approach could refer to
