Surcahrge from Sloping Backfill

[moe333]

Hello all,

I have a cantilever retaining wall with a varying length of level backfill then a 2:1 slope beyond, and I am trying to determine when I would need to add surcharge from the sloping backfill. Looking for something quick and dirty rather than Cullmans technique as I have a lot of conditions to look at.

As a screening method I was extending the active wedge behind the wall and seeing if it intersected the 2:1 slope. But portiions of the wall have a long footing so it makes a big difference if I extend the wedge from the end of the footing or the base of the wall. It seems to me that I would want to take it from the back of the footing when looking at sliding, but seems more logical to take it from the base of the wall when looking at overturning. Overturning and wall deflection are the critical aspects of this particular evaluation.

Any thoughts?

 

[jdonville]

I would think that for deflection, I think that you are correct that you would want to look at the soil immediately behind the vertical portion of the wall.

For overturning and sliding, you would want the portion behind the end of the footing, as the mass above the footing resists the overturning moment - it can't logically act to be both driver and restraint.

Jeff

 

[moe333]

My gut feeling is that where you have a long footing, the surcharge from a slope beyond the end of that footing would not contribute significantly to overturning.