Terraced Sheet Pile Walls

[structdb]

I am designing a terraced permanent sheet pile wall. There are two walls. The upper wall retains 7' and will be anchored. There is a slope from the front of the upper wall to the lower wall of 6' vertical to 14' horizontal. The lower wall retains 10'
Does anyone know of a reference that deals with terraced walls.

My first attempt has been to locate the point of zero moment in the lower wall, draw a sloping line back to the upper wall at the angle of friction and to ignore the passive pressure of any material above this line in the design of the upper wall.

Granular soil

I would appreciate any help.

 

[ishvaaag]

When designing sheet pile anchors, the section of ground dismissed for passive push is got by first tracing the angle friction with the vertical, to the surface, then (for horizontal surface at least, one sees in my texts) again the angle of friction with the horizontal, downwards. All soil beyond that last line is assumed to be ready to deliver passive push.

Professor Colling takes even as horizontal surface the top level of the (buried) anchoring sheet pile, anything above being thought as "a simple surcharge".

Anyway from you dimensions (if 6' and 14' are true dimensions) your second wall will be nailed outside this anchoring zone, so your approach looks reasonable. Otherwise, for this particular analysis, I would proceed as above.

Examine also what the web has to offer:

http://www.google.es/search?hl=es&ie=UTF-8&oe=UTF-8&q="double+sheet+pile"&meta=

 

[Focht3]

What has your geotechnical consultant had to say?



Please see FAQ731-376 by [blue]VPL[/blue] for tips on how to make the best use of Eng-Tips Fora.

 

[structdb]

My Geotechnical consultant hasn't been able to help me with this.

The concern I have is with the soil between the two walls and the passive pressure contribution of that soil.

 

[Focht3]

Hmmm,

Perhaps you need a better geotechnical consultant. After all, this is almost entirely a geotechnical issue. Unless, of course, s/he was only paid to drill and test - with no engineering budget. Under those circumstances, the "silence" is entirely understandable - and someone needs to provide them with additional funding. That local experience cannot be replaced by the contributors to this forum, no matter our collective education and experience...

Okay, we have the "above ground" dimensions. Where is the project located, and what are the below ground dimensions. What is the soil profile? ("Granular soil" doesn't tell me much.)

We need more information in order to help you -



Please see FAQ731-376 by [blue]VPL[/blue] for tips on how to make the best use of Eng-Tips Fora.

 

[structdb]

My geotechnical consultant's scope of work only included boring and testing. My scope of work includes the design of the facility including the sheet piling.

It was not my intention that the forum provide me with a design. I was just looking for some reference or guidance related to terraced sheet pile walls. But, since you asked, the borings indicate the following:

0' - 10' Silty Clay, N=5, Qu=.6 tsf, WC=24%
10' - 20' Sand trace gravel, N=19, WC=20%
20'- 35' Sand medium dense, N=15, WC=15%
35' - 50' Sand dense little gravel, N=40, WC=15%
50' Silty Clay hard some sand trace gravel, N=133, WC=15%, Qu=12.2tsf

The project is located in Southern Illinois near the Kaskaskia River.

 

[VoyageofDiscovery]

Hi Structbd,

Have you considered terraced mechanically stabilized earth walls as opposed to sheet pile walls?

Regards

VOD

 

[DRC1]

The orginal question pertained to the design of terraced sheeting. I agree with others in the forum that the design of sheeting is different from standard retaining walls. If you have done sheeting you can judge for yourself if you feel competent to do the work.
Terraced walls are rather complicated. I think the approach you mention does not follow the mechanics of a cantivered wall. Unless you need the terraces, i would design it as a single tied back wall. If I had to design it as a terrace, I would use the method to detrmine seperation for a tieback deadman and the wall to insure adequate passive pressure against the embedded wall and only active pressure against the exposed wall. This is explained in the Pile Buck Sheet Piling Design Book. Work with larger than normal factors of safety.

 

[ishvaaag]

structdb, and everyone reading my advice above:

I note an errata in my former advice: the lines are formed with

(pi/4-fi/2)

not with fi (angle of friction)