Tiered RC Cantilever Walls
Tiered RC Cantilever Walls
(OP)
My question is in regards to tiered walls, specifically RC cantilever walls but this could be applied to gravity / MSE walls as well.
It seems that typically the thrust due to the friction force is ignored when designing the lower tier. Normally only the bearing/soil pressure and possibly some of the passive pressure if the active / passive failure wedges over lap are applied to the lower wall. My question is why? Or maybe this should be done and if that is the case, then, how? I suppose you could use an elastic method for the case of a horizontal load on the surface of a semi-infinite mass.
Attache is a quick sketch to clarify.
Thanks!
It seems that typically the thrust due to the friction force is ignored when designing the lower tier. Normally only the bearing/soil pressure and possibly some of the passive pressure if the active / passive failure wedges over lap are applied to the lower wall. My question is why? Or maybe this should be done and if that is the case, then, how? I suppose you could use an elastic method for the case of a horizontal load on the surface of a semi-infinite mass.
Attache is a quick sketch to clarify.
Thanks!





RE: Tiered RC Cantilever Walls
A couple approaches are to use an equivalent slope or
Apply the bearing pressure as strip (or use your total vertical force as a line load) and apply the lateral force (Pa) as a uniformly distributed load on the back of the lower wall.
He also mentions that there is not much information out there on this situation.
This seems pretty conservative but I'll be interested to see how a few different approaches compare. I kinda wish I had one of those limit-equilibrium or Discontinuity Layout Optimization software packages (I'm not even sure what they do!)...I could play on there for days...
EIT
www.HowToEngineer.com
RE: Tiered RC Cantilever Walls
Confounding this is that the footing at each level imparts new "moments" trying to rotate the soil mass behind the wall below.
RE: Tiered RC Cantilever Walls
Other geotechnical aspects like rotational slope stability under static and seismic loads should be checked between neighboring walls & between upper most and lower most retaining walls.
RE: Tiered RC Cantilever Walls
FE -
What you're saying makes sense, thanks for the clarification.
I'd be interested that paper if you do come across it (I will look for it).
When you mention the 2x method, what are you referring to?
As for the 45 deg method. I assume this is the method where you distribute the force down at a 45deg. Then were it intersects the imaginary vertical plane at the back of the footing (or the stem for design of the stem) you apply the load as a uniform load load at that elevation.
Thanks again!
EIT
www.HowToEngineer.com
RE: Tiered RC Cantilever Walls
RE: Tiered RC Cantilever Walls
www.PeirceEngineering.com