## Cantilever Retaining Wall - Soil Pressure

## Cantilever Retaining Wall - Soil Pressure

(OP)

I have a question regarding the eccentricity of retaining wall footings, in regards to calculating footing bearing pressures.

Below is a quick overview of my procedure.

-neglect passive resistance

-neglect overburden on toe

-assume no surcharge loads

B = base width of footing

Mo = overturning moment

Mr = resisting moment

Ps = weight of soil + weight of concrete

I calculate the eccentricity:

e = (Mr - Mo) / Ps

I check if the eccentricity is in the middle third:

e > B/6 (if it is not in the middle third)

Lets say it is not in the middle third, for sake of discussion. I know that this is not always a deal-breaker, but lets say I want to get e < B/6. Are there any dimensional changes that I can make to the structure (excluding decreasing the stem height) that will decrease the eccentricity?

My initial guess was to increase B.

-if I increase the toe width, then Mr increases due to the larger moment arms

-if I increase the heel width, then Mr increases due to the weight of the additional soil on the heel.

In both of the above cases Mr greatly increases, thus increasing the eccentricity.

Am I looking at this incorrectly? Or is there no easy way to decrease the eccentricity on the retaining wall footing?

## RE: Cantilever Retaining Wall - Soil Pressure

## RE: Cantilever Retaining Wall - Soil Pressure

Sloped backfill is more complicated, where increasing the footing heel dimension increases both driving and resisting moments (not equally, though).

There are many retaining wall example problems in concrete text books, and the CRSI retaining wall (chapter 14) discussion and example is helpful and commonly referenced.

## RE: Cantilever Retaining Wall - Soil Pressure

www.PeirceEngineering.com

## RE: Cantilever Retaining Wall - Soil Pressure

I am using service loads.

If I continue have problems I will scan a copy of the calls.

Thanks