Retained Backfill Replacement for Conventional Gravity Walls

[RFreund]

The overall idea is to increase the height or stability of a conventional gravity wall where there is bad or even 'ok' sandy/clayey site soils behind the wall. Essentially the drainage aggregate or some type of granular material is placed behind the wall and sloped upward at approx a 1:1 to encompass the failure plane. Then the wall is evaluated using the soil properties of the granular material for computing the lateral pressures on the retaining wall (see attached).

EIT

http://www.HowToEngineer.com

 

[molerat2210]

Why was a 1:1 plane selected for the failure wedge? It is not clear what the goal is? Do you want to increase the height? How much?

After the new backfill is placed the wall will need to move to engage the friction in the backfill. Is it designed for at rest of active earch pressure? How much movement is acceptable?

Are there other issues: surcharge, scour, hydrostatic pressure? Are you using an friction or passive resistance at the base?

 

[PEinc]

RFreund, you really did not ask a question. However, what you described and showed in your attachment is not unusual. Sloping back the less competent, original soil and then backfilling the wall with more competent soil will give a more economical wall design and better performance. The same idea is used when a retaining wall is backfilled with Styrofoam (or equal) against the properly sloped original, less competent soil. Sufficient sloping of the less competent soil eliminates its high earth pressure so that the wall is designed for the lower pressure of the better soil. While a 1:1 slope may encompass the failure plane of the more competent soil, the slope of the less competent, original soil should be flat enough that its slope is stable with a satisfactory safety factor. Then, the better backfill can be placed.

If you are trying to increase the height of an existing retaining wall, replacing the less competent soil behind the wall can certainly help.

http://www.PeirceEngineering.com

 

[RFreund]

Thanks for the responses. Somehow my second paragraph was left off. I just wanted to get some feed back on the concept. PEinc _ You answered most of my questions / concerns. The more i thought about it the 1:1 was zort of arbitrary and what u saidmakes sense. The goal is to achieve taller wall ht wifhout using geogrid.

EIT

http://www.HowToEngineer.com

 

[RFreund]

Yikes, sorry last post was from my phone.

EIT

http://www.HowToEngineer.com