Hello All, I'm engineering a ret

[Travis Roberts]

Hello All,

I'm engineering a retaining wall that is retaining 36" of soil with a residential driveway surcharge. The ground slopes away from the existing driveway at about a 2:1 slope. (Existing wall was damaged in a fire and is being tore out and a new one constructed).

My question is this. is it permissible to have the footing rest on grade and have a 6" wide keyway extend 12" deep into the soil to achieve the general 12" depth requirement for footings?

The associates I have that did the site visit seem to think there won't be enough soil in front of the toe anyways to provide any kind of sliding resistance, but the toe is still needed to be under the allowed soil bearing values. I will try and upload a sketch of the wall for clarity [URL unfurl="true"]https://res.cloudinary.com/engineering-com/image/upload/v1669542870/tips/30_inch_detail_sketch_rev_2_ijpmof.pdf[/url]

The dirt on the left side of the wall isn't drawn in....but picture it starting at the top left corner of the footing and falling away at a 2:1 slope.

Thank you for any and all responses

 

[EireChch]

The portion of soil in front of the wall has no influence on sliding, provided the 2:1 slope is stable, which it should be at such a slope. Sliding is just wall weight times tan of your interface friction angle.

If you were relying on passive resistance then the material in front of the wall is reduce which reduces your passive resistance.

I would think what you provided is more than enough

 

[SlideRuleEra]

Sliding is not to only failure mode for a retaining wall.
Also check for overturning... the design shown may not (probably will not) pass:

 

[LittleInch]

An overall picture / drawing etc would be very useful t understand the context here.

Are you planning on building this in two stages? Might need to thing about a water stop plate to stop leakage at the base of the wall?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[dik]

What is the level of the soil/whatever on the LHS of the retaining wall? Is is subject to frost heave? Is it soil? or asphalt driveway? or something else... if pavement, there should be a 'buffer' of granular material between the top of the retaining structure and the pavement.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[PEinc]

Looks expensive for only a 30" height of retained soil.

http://www.PeirceEngineering.com

 

[BridgeSmith]

I agree with SRE that it's doubtful the configuration shown would be stable against overturning. Walls like that, even small ones, have a heel that's held down by the soil behind the wall. If you're unable to put a heel on it, you could possibly extend the stem/shear key deeper, so it would functionally be a non-gravity wall (similar to a cantilever sheet pile wall).

Rod Smith, P.E., The artist formerly known as HotRod10

 

[PEinc]

Why are you not considering a segmental block wall? With having only 30 inches of retained earth, you might need little to no geogrid reinforcement.

http://www.PeirceEngineering.com

 

[BridgeSmith]

With having only 30 inches of retained earth, you might need little to no geogrid reinforcement.

The small precast concrete block walls (Keystone, etc.) can usually go up to about 4' high as a gravity wall.

Rod Smith, P.E., The artist formerly known as HotRod10

 

[PEinc]

BridgeSmith, I agree. That's why I said, "...you might need little to no geogrid reinforcement."

http://www.PeirceEngineering.com

 

[BridgeSmith]

PEinc, I was just trying to indicate that for a 30" wall it's very probable that it could be done as a gravity wall with blocks, where your wording made it sound like a more slim possibility.

Rod Smith, P.E., The artist formerly known as HotRod10

 

[PEinc]

I understand. However, without sufficient information, I did not want to say grid definitely wasn't needed.

http://www.PeirceEngineering.com

 

[Travis Roberts]

I'd like to thank everybody for their responses.... I appreciate your time spent. Really enjoy this site.

Cheers