Tieback designs

[tre5205]

When doing tieback designs -does one need to check embedment is deep enough to ensure passive resistance? It seems most designers dont -and if you are suppose to how does one go about it solving it?

Ita not like cantilever shoring on the equilibrium method.

Your help is greatly appreciated.

Tre

 

[PEinc]

Please explain further. Are you refering to grouted tiebacks or mechanical tiebacks like helicals, Manta Rays, or Sting Ray? Are you refering to a tie rod with a buried deadman?

Passive resistance is not a design consideration in grouted anchor design. It is for tie rods and deadmen. It is not for the mechanical anchors as long as the bearing member (helix or plate) is far enough behind the theoretical failure plane to meet the manufacturer's recommendations.

http://www.PeirceEngineering.com

 

[tre5205]

I am referring to grouted tiebacks. I guess im not sure why some designers that have two rows of tiebacks same theoretical situation but one designer has the toe embedment deeper than another. How does one feel comfortable?

 

[jagti]

I would think Toe Embeddment would be dependent upon Long term Settlement & Bearing Capacity Analysis, Toe Erosion potential etc

 

[FixedEarth]

Tre;

The best way you to feel comfortable with a new topic like tieback wall design and review of various software results is to study this subject in detail. Try the books by Tschebotarioff. He did a lot of research and publications in earth retaining structures. Try his 1951 book, "Soil Mechanics, Foundations and Earth Structures". More recently, Azizi's "Geotechnical Design" book, 2007 is very useful.

When I first got into this topic, I saw all kinds of methods and output by several shoring designers. No two calculations were the same or even with 5% of each other. It only made sense after I read half a dozen books and settled on one method of analysis.

 

[tre5205]

Thanks for the replies.

FixedEarth- thats exactly it every software for the same given problem gives different results and not even that close for that matter. I realize there is different methodologies for different software.

Thanks,
TRE

 

[GeoPaveTraffic]

For most showing problems there are several acceptable, i.e. valid solutions. The trick is to develop a solution that is both cost effective, within the means of the contractor, and works. This is not always as easy as it sounds.

Generally speaking, any design the meets static equilibrium without over stressing one of the design elements works. A lighter weight solider pile may require two levels of anchors where a heavier pile only needs one level of anchors. Also, with more levels of anchors your embedment length decreases.

This is the point of the design. To find the best balance.

Don't rely too much on software. It only does what you tell it and if you tell it to do something stupid, then that is what it will do.

Good Luck.

Mike Lambert