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Re: Sloping Footings

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Novak, Dan wrote:
> We are working on an access road/driveway and will require a 5 foot high
> retaining wall. The road slopes in a vertical curve as much as 20%.
> Is there a precedent for the design of a spread footing for a retaining wall
> that is sloping up to 20% in the direction parallel to the wall?  Section
> 1806.4 of the 1997 UBC states that foundations for all buildings where the
> surface of the ground slopes more than 10% shall be level or stepped. Does
> this necessarily apply to retaining walls ?  Do DOT's or one of the
> county road departments have a standard that addresses this question ?
> What are the issues other than sliding parallel to the footing and
> construction difficulties that may effect the foundation?
> Thanks for your input.
> Dan Novak ASL Consulting Engineers  "Former lurker"
1.	Step the footing.  I wouldn't trust construction conditions/methods
to validate a sloped bottom sliding analysis even for a 5ft wall.
2.	Take care to properly drain the system (behind and under the
structure).  If cold climate, weep holes can form ice on the driveway
which is just asking for a lawsuit.
3.	Also, question the 20% slope.  My experience is that over 15% causes
many problems the Owner has to deal with every day.  That kind of design
leads to complaints (or worse).  Make sure the Owner/Client fully
understands the implications of a 20% slope and signs off.

Good luck.

Laurence Oeth, P.E.