Tie back wall design without toe active pressure

[TSGEIT]

We are designing a restrained tied back wall where the footing is exposed, i.e. no toe active pressure to resist sliding. This design is temporary, while repair work is being done to the surrounding structure (including replacing an exisitng base slab that is currently restraining sliding of the wall). Currently we have created a spreadsheet to analyze the bearing pressure, required tieback load capacity, and resistance to sliding. We are having problems obtaining adequately low bearing pressure at the heel of the wall, as the tieback is resisting lateral loads only.

We have tried using Retain Pro, however the latest version only allows a restrained height of 7 feet above the footing, and emails to their help desk indicate that the restrained condition was intended for basement walls. Any suggestions/reference documents on how to model this type of retaining wall would be greatly appreciated.

 

[PEinc]

You need to post a sketch.

http://www.PeirceEngineering.com

 

[fattdad]

I think you mean, "passive" if you are referring to a resisting force. I really hope the tiebacks are deriving their entire capacity behind the Rankine failure plane also. Bear in mind, often tiebacks are installed with an angle downward from the horizontal. If you expose the footing, the vertical vector from the tieback force will add to the "bearing" stress. You'll loose capacity from the reveal and you'll gain loading from the tiebacks. You can install them horizontally, but they'd have to be longer to get behind the Rankine failure plane.

I hope your free body diagram agrees with your spreadsheet and computer programs. If not, trust your FBD.

f-d

¡papá gordo ain’t no madre flaca!