Memorandum

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.

Background

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.

JK:dsb
BK

cc:    J. Weigel, Bridge and Structures - 47340
        F. Higgins, Bridge and Structures - 47340