Lateral load due to surcharge 2

[pelelo]

There are many closed and interesting forums about lateral loads due to surcharge.

I know there are some confusions in the Poulos and Davis book: "Elastic solutions in soil and rock mechanics" about the angles (alpha and beta), which one you need to use in degrees and in radians.

Another reference I use is the one posted by FixedEarth " Substructure analysis and desing" by Paul Andersen, to me, I get more reasonable results than using Poulos and Davis approaches.

And I guess there are few additional references with slightly different approaches.

Anyways, the question that I have is, are these formulas applied no matter what the soil strata I am dealing with??, If I have a sandy stratum it would have the same effect as If i have a multilayered system (sand, clay, silt, gravel, etc)?. Or does these approaches keep some conservatism?

Thanks

 

[FixedEarth]

Very interesting question. The elastic equations modified by experiment seems to be the most popular, as you have stated. This is what Spangler in 1930's and Terazghi in
the 1950's have confirmed.

As you know, the elastic equations depend on poisson's ratio, and is a number that is inexact. I would say the worst case is when you have a high intensity strip footing that is very close proximity to the retaining structure. Regardless of uniform soil or layered soils, the stress due to surcharge will take the shape of a question mark. So our interest is in the upper 2m or so.

If Layer 1 is much more stiffer than Layer 2 or Layer 1 is deeper than 2 m, the equation you referrenced should be sufficient. If, however, soil stifness decreses rapidly, you could use the poisson's ratio for the soil at 2m depth, for example, and this will make up for the slightly stiffer overlying soil.

If the earth retaining structure is very sensitive to movements, you can always do a numerical study of the layered soil system.

http://www.FoundEng.com

 

[FixedEarth]

Pelelo;

Attached are the equations extracted from the NEW 2011 Caltrans Trenching & Shoring Manual.

The strip and line loads, I was able to match. However, their point load stresses seem to be on the high side-Let me know what you or the other Geotechnical engineers figure out.

http://www.FoundEng.com