10ft Retaining Wall With only 12" soil behind it
10ft Retaining Wall With only 12" soil behind it
(OP)
Hi Everyone.
Here's the problem. I have approx 10ft tall retaining wall. Behind the wall, there's stable limestone stratum, does not need a wall because it can retain itself.
However, there will be a gap between the back of the wall and the face of the rock, about 12", which will be filled with gravel.
So, it's a 10ft tall wall which is only retaining a 12" wide x 10ft tall "column" of soil per foot of wall length.
I'm trying to figure out what the pressure will be behind this wall. I know it must not be gamma x H because it's only 12" of soil... so what Is the pressure behind the wall?
Thanks.
Here's the problem. I have approx 10ft tall retaining wall. Behind the wall, there's stable limestone stratum, does not need a wall because it can retain itself.
However, there will be a gap between the back of the wall and the face of the rock, about 12", which will be filled with gravel.
So, it's a 10ft tall wall which is only retaining a 12" wide x 10ft tall "column" of soil per foot of wall length.
I'm trying to figure out what the pressure will be behind this wall. I know it must not be gamma x H because it's only 12" of soil... so what Is the pressure behind the wall?
Thanks.





RE: 10ft Retaining Wall With only 12" soil behind it
Mike McCann
MMC Engineering
RE: 10ft Retaining Wall With only 12" soil behind it
f-d
¡papá gordo ain't no madre flaca!
RE: 10ft Retaining Wall With only 12" soil behind it
RE: 10ft Retaining Wall With only 12" soil behind it
And yes, thanks for bringing up the drainage, it will be gravel with a perforated pipe at the bottom.
RE: 10ft Retaining Wall With only 12" soil behind it
RE: 10ft Retaining Wall With only 12" soil behind it
Michael.
Timing has a lot to do with the outcome of a rain dance.
RE: 10ft Retaining Wall With only 12" soil behind it
Calculate the active earth pressure at the depth of 2 ft.
For gravel use a phi=38 degrees, so Ka=0.238 and Eh(at 2 ft)= 59.5 pcf. That's the maximum value of earth pressure below the depth of 2 ft. You see when you say the rock is providing no earth pressure, below the depth of 2 ft the only affect on the Rankine wedge is that the wedge includes more rock, which provides no new horizontal load.
Considering the above posts, I'd now suggest that you use 60 psf as a uniform load below the depth of 2 ft (or for the whole wall), depnding on how refined you want to be.
Hope this helps. Try making a drawing, it may become clearer.
f-d
¡papá gordo ain't no madre flaca!
RE: 10ft Retaining Wall With only 12" soil behind it
I did a wall just like this a few years ago. The geotech on the project gave me this drawing showing what the wall pressure should be.
RE: 10ft Retaining Wall With only 12" soil behind it
h
RE: 10ft Retaining Wall With only 12" soil behind it
RE: 10ft Retaining Wall With only 12" soil behind it
So, soil pressure must me related to the mass of it behind it...
RE: 10ft Retaining Wall With only 12" soil behind it
RE: 10ft Retaining Wall With only 12" soil behind it
RE: 10ft Retaining Wall With only 12" soil behind it
RE: 10ft Retaining Wall With only 12" soil behind it
http:
Should help.
RE: 10ft Retaining Wall With only 12" soil behind it
f-d
¡papá gordo ain't no madre flaca!
RE: 10ft Retaining Wall With only 12" soil behind it
If the fill is tailgated, it becomes analogous to the narrowbunker in which case, Janssen's formula for narrow bins would apply. The result would not be too different. Janssen recognized that if the normal methods, say Rankine were used, the increasing lateral pressure and the friction would cause bridging of the fill material, but material does flow in bunkers and silos so he derived his formula.
Janssen's formula yields a curved line, rather than the straight line of Rankine, et al. See the attached link, below, for a diagram. There are other places on the web where it is explained, do a search.
The above is for anyone who wants to explore the behavior, my guess is that fifty or sixty lbs is about right.
Michael.
Timing has a lot to do with the outcome of a rain dance.