TO: All Design Section Staff FROM: J. Kapur Phone: 705-7209 DATE: May 24, 2001 SUBJECT: Abutment Backfill Load Case
This memorandum applies to all cantilever and L-shape abutments.
During the abutment design, a load case shall be considered to check the stability of abutments after placing backfill but prior to superstructure placement. This load case is intended as a check for a temporary construction stage, and not meant to be a controlling load case that would govern the final design of the abutment and footing. If the abutment is found to be satisfactory, a note will be added to the general notes in the contract plans and the contactor will not be required to make a submittal requesting approval for early backfill placement. Otherwise, the backfill placement for the stability calculations shall assume a loading of 30 lb/ft3 equivalent fluid pressure and include at least 2-foot for the backfill placement equipment as covered by the WSDOT Standard Specifications article 2-03.3(14)I.
We are receiving several submittals from the contractors requesting approval for backfill at abutments prior to superstructure placement. To streamline this process for the contractors, during the design phase, the abutment stability shall be checked, both for overturning and sliding, without the superstructure in place.
If you have any questions regarding these issues, please contact Bijan Khaleghi at 705-7181.
cc: J. Weigel, Bridge and Structures - 47340
F. Higgins, Bridge and Structures - 47340