Mohr circles and upper bound plasticity

[MutleyC]

I'm trying to solve a passive retaining wall problem using upper bound methods but I'm a bit confused by one aspect.

Knowing the soil friction angle phi', a single stress pair (sigma,tau) at one critical point, and the angle of the plane on which this stress pair is acting, is it possible to draw the Mohr circle for the stress state at this point, and thereby determine the angles of the shear failure planes?

I have been led to understand that it is, and that is therefore possible to determine rupture planes and discontinuity fan, and thus an upper bound mechanism.

Any help would be gratefully accepted!

Cheers
Mutahar

 

[fattdad]

Just an observation, as I'm not sure I understand the original question: To me a single point (i.e., what you describe as sigma/tau) seems more like a P-Q point, which is the apex of a given Mohr's circle and the corresponding shear strength for that circle. If you draw a "failure" line from the ordinate to this single point you are depicting the angle "alpha" not the angle "phi". As such, a geometric conversion is needed.

Another observation: I'm not sure what a "passive" retaining wall refers to. . . I am familiar with active pressures, at-rest pressures and passive pressures. All of which can relate to a given retaing wall design. Base shear can also be a factor.

It may help this discussion if you explained the problem that you are trying to solve.

f-d

¡papá gordo ain’t no madre flaca!