## Correlation between horizontal and vertical permeability coefficients

## Correlation between horizontal and vertical permeability coefficients

(OP)

Hi!

Is there a reference to use for determining a correlation between horizontal and vertical permeability coefficients for different soils?

Thanks,

BK

Is there a reference to use for determining a correlation between horizontal and vertical permeability coefficients for different soils?

Thanks,

BK

## RE: Correlation between horizontal and vertical permeability coefficients

D. Bruce Nothdurft, MSCE, PE, PG, M.ASCE, etc, etc,...

Principal Engineer/Geologist

Atlantic Geoscience & Engineering

Charlotte, NC

## RE: Correlation between horizontal and vertical permeability coefficients

And as Bruce asked, "What do you want to do?"

Please see FAQ731-376 by

VPLfor tips on how to make the best use of Eng-Tips Fora.## RE: Correlation between horizontal and vertical permeability coefficients

Any guidance would be appreciated.

Thanks again.

:(

## RE: Correlation between horizontal and vertical permeability coefficients

Good Luck!

## RE: Correlation between horizontal and vertical permeability coefficients

The Cv value you mention has nothing exceptional and I would not go for more than 5 for this type of value.

If your project is really big you can think about a trial zone to check the real consolidation properties.

if it is not the case vertical drains are cheap enough to consider a coefficient of 1.5 or 2. Check also if you want to take a chance if you can put things right again by increaing the height of surcharge if it does not work and consolidation time increases too much.

## RE: Correlation between horizontal and vertical permeability coefficients

Thanks again. The clay encountered in this region, is glacial in origin, the sand, silt and clay components vary between 20%-40%, which is characteristic of glacial clayey tills. The LL, PL and PI are about 30-35, 15-20 and 15-25 respectiviely.

Hope this helps.

BK

## RE: Correlation between horizontal and vertical permeability coefficients

The bottom line is that the fewer the actual clay mineral content, the less difference you will see between the vertical and horizontal permeability.

The absolute best way (from a hydrogeologist's viewpoint) is to conduct a pumping test!

D. Bruce Nothdurft, MSCE, PE, PG, M.ASCE, etc, etc,...

Principal Engineer/Geologist

Atlantic Geoscience & Engineering

Charlotte, NC

## RE: Correlation between horizontal and vertical permeability coefficients

Can you provide the stratigraphy of the site as it woulfd be of interest to know if there is a drainage layer with depth as well.

## RE: Correlation between horizontal and vertical permeability coefficients

This is the table extracted from "prefabricated vertical drain: Vol 1, engineering guidelines" by Rixner J.J, Kraemer S.R & Smith A.D

Soil Kh/Kv

No evidence of layering (partially

dried clay has completely uniform appearance) 1.2+-0.2

No or only slightly developed macrofabric (e.g 1 to 1.5

sedimentary clays with discontinous lenses and

and layers of more permeable soils)

Slight layering (e.g sedimentary clays with 2 to 5

occasional silt dusting to random silty lenses)

Fairly to well developed macrofabric (e.g 2 to 4

sedimentary clays with discontinous lenses and

and layers of more permeable material)

Varved claus in Northeastern US 10 +- 5

Varved clays & other deposits containing embedded 3 to 15

& more or less continous permeable layers

(soft clay is defined as clay with an undrained shear strength of less tha 1000 psf)

In addition, a research done by Prof Bergado (Asia Institute of Technology) for the bangkok soft clay showed there is a big variation between the lab test and field test. as his result Ch(field test)/Ch(lab test) = 4 and Cv(field)/Cv(lab) = 26 for the Banhkok soft clay.

Also he got Kh/Kv = 4-10.

Hope this help

## RE: Correlation between horizontal and vertical permeability coefficients

Thank you for your post. It is just what I waslooking for.

CHBK

## RE: Correlation between horizontal and vertical permeability coefficients

In response to your question, the clay/stiff till (N<12) layer is underlain by a 4.2m thick firm glacial clay layer (14<N<50). Although the logs call it out as "sandy" the tests don't seem to support it. Also, there is no evidence that the sand seams if any are sufficiently continuous to permit drainage. Therefore, for consolidation purposes, I have been assuming single drainiage to a granular drainage blanket installed on the surface.

Hope this helps.

CHBK

## RE: Correlation between horizontal and vertical permeability coefficients

The main thing is not to overestimate Kh; its ok to underestimate it because its ok if the consolidation happens ahead of schedule with less surcharge because that saves money. Your Kv seems really high for a true clay (about 100x if its consolidated), so you could just use your Kv as your Kh, predict required surcharge and time, then monitor actual settlement and calibrate your Kh assumption with it.

D. Bruce Nothdurft, MSCE, PE, PG, M.ASCE, etc, etc,...

Principal Engineer/Geologist

Atlantic Geoscience & Engineering

Charlotte, NC