Lateral Deflection of Retaining Wall 1

[Son of a Bridge]

Is there an equation (or any reference material) that determines the maximum lateral deflection at the top of a retaining wall (due live load surcharge and horizontal earth pressure)?

Not sure if I can use the deflection equations for a cantilever beam from AISC Table 3-23 due to the soil.

Feel free to provide a list of references that provide this information.

Any help is appreciated.

Thanks,

Danny

 

[KootK]

The CRSI manual on retaining walls addresses this in some fashion I believe.

 

[Tomfh]

There's no simple formula. The wall itself deflects/bends under loads, but more importantly the soil deforms. Some soils have to deform a lot to achieve the assumed active pressure coefficients. So the wall simply rotates until the stresses reduce to the level the wall is designed for. Hence a lot of walls leaning quite a lot!

 

[Lomarandil]

For a pure retaining wall (not an abutment or foundation of some sort), I'm not aware of any definitive upper limit on deflection. In my experience, it's most often governed by the aesthetics or "what doesn't look like the wall is about to collapse?". Of course, if the wall interacts with or supports some structure (e.g. your live load surcharge), that can create a deflection criteria. AASHTO essentially punts to engineering judgement based on consequences of movement.

You can use ordinary deflection equations to see how your wall will perform (if appropriate, adjusting for cracked stiffness), keeping in mind Tomfh's note about mobilization of earth pressures. NAVFAC 7.2 has some guidance about what types of deflections/wall rotations correspond to what earth pressures based on soil types.

----
just call me Lo.

 

[r13]

As the minimum, we at least provide 1% slop on the front wall face. Sometimes more.

 

[Son of a Bridge]

Thank you all for the responses.

Yes, originally I was going to use the deflection equations for a cantilever beam from AISC, but I realized the soil needs to be considered.

I will look into the CRSI manual for the deflection equations. Hopefully two separate equations are available (live load surcharge and horizontal earth pressure).

I need to make sure the retaining wall reaches the active condition. Otherwise, the at-rest condition will need to checked.

Danny

 

[r13]

Danny V,

Note that it is advisable that, for important earth retaining structures, always design for at rest condition. Soil behaviors are hard to predict, we all need good sleep at night