Geocomposite V.S. Wick Drain Strips

[shadywai]

Hi guys,

I am now doing a soil nail walls design, and i am wondering that can i replace 4-in wide wick drain with 16 to 24-in geocomposite behind the shotcrete wall.

In FHWA soil nail walls manual, circular no.7, it just mentioned about geocomposite drainage design.

Thank you.

 

[PEinc]

Geocomposite drain is frequently used. I never saw 4" wide wick drains used behind a wall facing.

 

[emmgjld]

In my opinion, The geocomposite should be the primary design material for drainage.

The wick drain material should be the option, only when it is confirmed that little water is anticipated. Also, the wick drain material is more likely to experience damage during the shotcrete application.

 

[BigH]

good point emmgjld - the shotcrete has a 'ell of a force coming out of the hose!

 

[shadywai]

Thank you very much, guys,

After looking at the comments, i have some other questions here.

In the design manual, they said geocomposite needs to be overlapped for 12-in MIN., will it be hard for 4-in. wide wick drain when doing this.

Emmgjld, you said wick drain is more likely to experience damage, what is the difference in material between geocomposite & wick drain?

If the material is "softer" in wick drain, will the kinked condition affect the flow rate efficiency?

Thanks.

 

[PEinc]

In my opinion, wick drains will be too small for wall drainage. They will not have the flow capacity that geocomposits have. I would not use a product that was not intended for wall drainage use. Wick drains are strong. They are just too small and their flow paths are too small.

 

[EdGeotech]

I agree with PEinc and emmgjld. I would definitely go with the drainage geocomposites over the wick drains. It would be difficult for me to stray from the industry standard for drainage in soil nail construction especially since its been used successfully for a number of years. Also, since the wick drains are relatively small, I think it would be difficult to secure them enough to keep the shotcrete from getting behind it.