Light weight fill and retaining wall loads?
Light weight fill and retaining wall loads?
(OP)
Hi All,
So when you are using a lightweight fill such as blocks of extruded polystyrene on the fill side of a retaining wall do you treat the lateral earth pressures on the wall as you normally would? Or do you negate or say there is no lateral earth pressure on the wall due to the use of the light weight fill? Thanks.
So when you are using a lightweight fill such as blocks of extruded polystyrene on the fill side of a retaining wall do you treat the lateral earth pressures on the wall as you normally would? Or do you negate or say there is no lateral earth pressure on the wall due to the use of the light weight fill? Thanks.






RE: Light weight fill and retaining wall loads?
RE: Light weight fill and retaining wall loads?
One possible change is that if the lightweight fill is sufficiently compressible, it might allow the use of the active lateral coefficient Ka, instead of the at-rest coefficient Ko.
Brian C Potter, PE
http://simplesupports.wordpress.com
RE: Light weight fill and retaining wall loads?
RE: Light weight fill and retaining wall loads?
RE: Light weight fill and retaining wall loads?
RE: Light weight fill and retaining wall loads?
The other issue is economy. When polystyrene is used as a void former in concrete structures, it is to save mass rather than concrete per se. As I understand it, polystyrene costs about the same as concrete on a volume basis. If that is correct, it would cost a lot more than earth fill. So why do it?
RE: Light weight fill and retaining wall loads?
For those that believe you don't need to design for full 'normal' lateral pressures, but some portion of it, quess my question is 'What portion and how do you know it's that portion, percemtage or fraction?.
briancpotters reply seems the most straight forward, 'If's there's no lateral pressure, why do you need a retaining wall?', to paraphrase.
Hokie66 of course I agree, stability becomes the problem when you have no mass on/over the heel. Unless of course one believes there is no lateral force.
RE: Light weight fill and retaining wall loads?
RE: Light weight fill and retaining wall loads?
EIT
www.HowToEngineer.com
RE: Light weight fill and retaining wall loads?
No the styrofoam fill is not being sloped as mentioned by sructSU10. The proposal is to install 4'x4'x8' blocks vertically up the back face of the retaining wall, the foam will come 8' out from the back of the wall, the 8' block direction is parrallel to the length of the wall and then backfill against the foam. The Contractors proposal makes little sense to me. The lateral load can not disappear in to the foam. The wall is 14' high. The backfill will be 2" minus crushed stone. The natural deposit is a compact silty-sand with the natural WT below the walls footing. Excavation into the slope is 3:1.
RE: Light weight fill and retaining wall loads?
Thanks for the leader to the I15 in Utah. In that case, it looks like the focus was on roadway embankments, and limiting consolidation in the underlying clays...a noble objective. The "walls" were actually facing panels, similar to Reinforced Earth facades. Not cantilevered retaining walls, but the soil part of the embankments were sloped, so the styrofoam is wider as you go up.
http://www.civil.utah.edu/~bartlett/UDOT/UDOT%20EP...
RE: Light weight fill and retaining wall loads?
In that case, I guess I too really don't see the benefit.
EIT
www.HowToEngineer.com
RE: Light weight fill and retaining wall loads?