Tryingtolearn
Structural
- Oct 13, 2023
- 1
I have a little bit of an unusual situation. I am designing a spread footing abutment for a bridge on rock. The new approach roadway will be on rock. At the back of the abutment the rock will be cut down and the base of the abutment will sit on the rock. See attachment for the cross section to help explain. There will be a 2' gap between the back of the abutment and the rock face. That 2' gap will be filled with granular fill. For bearing pressure, over-turning and sliding - how you you treat the pressure on the back of the wall from this small value of granular backfill? I just assumed it was like a normal abutment and got my normal at rest pressure as this is conservative. For the constructed condition there are no issues and everything passes. However during construction sliding does not work as the abutment itself is pretty light (once the bridge is constructed sliding is not an issue). My gut says there is actually no issue with sliding as the actual volume of fill behind the wall is much smaller than the typical active wedge assumed when I work out my at rest pressure (P = 1/2 Ko ps h^2). However I would like to put some numbers to it to show it. Any ideas?
I can always just tell then not to backfill the abutment until the superstructure is erected but would prefer to understand the loading first.
I can always just tell then not to backfill the abutment until the superstructure is erected but would prefer to understand the loading first.
