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Reduced anchor wall capacity

Reduced anchor wall capacity

Reduced anchor wall capacity

(OP)
I am designing a sheet pile retaining wall that will utilize a continuous sheet pile anchor wall.  The wall is being constructed along an existing sloped roadway embankment to facilitate widening of the road and the anchor wall will be located under the existing roadway.  There are some site constraints, though, that may require that a portion of the anchor wall to be placed inside the minimum spacing required for full mobilization of the resisting pressure.  Is there an accepted method for calculating the reduced capacity of the anchor wall?  I've seen references to procedures by Terzaghi but have been unable to put my hands on anything!  Any input is appreciated.

RE: Reduced anchor wall capacity

I would dismiss any resisting force coming from the height of sheet outside the allowed anchoring zone (that is, the one that allows development of the full passive push) whilst keeping the reaction force centered on the tie.

RE: Reduced anchor wall capacity

Yes. Get the Pile Buck Steel Sheet Piling Design Manual. (www.pilebuck.com). It is a very good resource for sheet pile design. It explains how to calulate the resistance of a sheet pile anchor wall and gives the correction if the wall is placed inside the minimum seperation for full passive pressure on the anchor wall.

Good Luck.

RE: Reduced anchor wall capacity

The Pile Buck Sheet Piling Design Manual is not an appropriate or current reference for designing a permanent tiedback retaining wall for supporting a highway.

Check out FHWA Geotechnical Engineering Circular No. 2, Earth Retaining Systems (FHWA-SA-96-038) and Geotechnical Engineering Circular No. 3, Ground Anchors and Anchored Systems (FHWA-IF-99-015).

Pile Buck's manual is the old US Steel Sheet Piling Design Manual.  It is geared toward bulkheads with triangular soil pressures.  Nowadays, most tiedback walls, especially highway walls, are soldier beam and lagging walls, tiedback as necessary, with precast or cast-in-place concrete facings.  In the USA, highway walls must be designed for AASHTO criteria.

RE: Reduced anchor wall capacity

DRC1 is correct though that Pile Buck does have good information on deadmen, tie rods, pressure coefficients, etc.

RE: Reduced anchor wall capacity

PEinc is correct - FHWA is a better reference.  Don't use Pile Buck for your problem -



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

RE: Reduced anchor wall capacity

Pile Buck is how sheet piling is built. FHWA is how designers think it si being built

RE: Reduced anchor wall capacity

Well, perhaps DRC1 is correct, and the Pile Buck / US Steel manual dominates design procedures in some areas.  But that doesn't change the fact that the manual perpetuates many bad design practices...



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

RE: Reduced anchor wall capacity

Luke648 didn't say for whom the wall was being designed, who would approve the design, or who owned the road.  It is my experience that if a municipal, state, or federal government is involved, the wall will need to be designed to AASHTO and FHWA requirements.  Pile Buck does not fully address these requirements.  However, Pile Buck could probably be used for any design items that are not addressed by AASHTO or FHWA.  Pile Buck is a very good reference.  It just isn't always acceptable for highway design.

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