Boussinesq Surcharge Formulas
Boussinesq Surcharge Formulas
(OP)
In using conventional Boussinesq surcharge formulas, I'm finding that the formulas are erroneous in that there is no upper limit to the applicability. In other words, I could place a strip load surcharge half a mile away from a 50' high wall and still see appreciable lateral loads being imposed onto the wall. How do others handle this situation in applying a reasonable upper limit?
Thanks!
Thanks!





RE: Boussinesq Surcharge Formulas
we had a string of threads on horizontal loads on retaining walls owing to surface loads. No doubt there are a range of potential problems (i.e., do you multiply the loads by 2).
f-d
¡papá gordo ain’t no madre flaca!
RE: Boussinesq Surcharge Formulas
Angles are definitely acute but they do have an impact nonetheless. And yes, I am using the notorious factor of 2 in the equation posted below.
Sigma = (2*q/PI)(Beta - Sin(Beta)Cos(2*Alpha))
The half mile was a bit of an exaggeration but it does highlight the scenario. Here's a set of parameters for discussion:
1000 PSF surcharge, 1000 foot wide strip, set back = 500 feet, wall height = 50 feet
Intuitively I would expect there to be a negligible effect on the wall at this distance but my results indicate it is about 15% of a full uniform load. Now if I increase the setback to 1000 feet, it's still about 6%.
I recall some theory that surcharge loads beyond the active plane are generally disregarded. Perhaps this applies?
RE: Boussinesq Surcharge Formulas
RE: Boussinesq Surcharge Formulas
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RE: Boussinesq Surcharge Formulas
As for an upper limit - you can use the failure plane/angle by Coulomb or by trial wedge (Culmann). A 1:1 failure angle is frequently used and is usually conservative. Terzaghi gives some insight as well but I need to dig this up again. There are a couple good discussions on here about this topic as well.
Side note:
I have a problem with the strip load equation typically used (also referenced above by Poulos and Davis) in that it does not produce similar results as if you were to discretize the strip load and sum the pressures from a series of point loads from the 'original' point load Boussinesq equation (as Suggested by Bowles in his 4th Edition) . I have a post on my blog about this that I can like to later.
EIT
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