I am examining a case in which there are not available undisturbed samples and I got just some indication of under-consolidation of a clay-bearing breccia (very low undrained strength with reference to effective in situ stress, as well as the analysis of some compression curves for swelling test...
Thank you to Maccoy (as well as to BigH).
I found also in the Book "Soil Mechanics" (Verruijt, 2001) the following similar equation:
su = c' [cos phi'/(1 ? (1/3)sin phi')] + p0' [sin phi'/(1 ? (1/3)sin phi')]
In this equation there is Af=1/3 and then a more general formulation should be obtained...
A request to BigH: unfortunately I did not find the book of Lambe & Whitman. Please, have you any possibility to report the equation 28.1 that you have mentioned for c' different than zero?
Thank you very much in advance..
Jordan
Thank you very much to BigH, Fattdad and to all of you for the very interesting discussion. I am in some way conforted that maybe my question was not so banal as I was afraid.
Ciao!
I have to think in detail to your suggestion, but my first impression is that it is not so far from what I have seen in the pubblications as I have reported in my first post. If I am understanding, this seems in contrast to the opinion of Moe333 (that, incidentally, was also my original...
Thank you for your answers, but I am not sure that the concept of my question was clear: I am not generally asking how to determine the undrained strength (it is clear what Fattdad says..), but if it may be theoretically derived from the effective shear envelope (for a certain stress condition)...
Dear Friends,
I have the following theoretical doubt and maybe I am doing a stupid question: let you suppose that by means of triaxial CU tests the effective shear strength parameters (c' & phi') of a saturated clay have been derived. Could I derive from the effective envelope the undrained...
I have written also to Ted Brown and he answered that the boundary porosity should be in effect the ratio B/A, where B is the solid to solid contact area and A the total area. Therefore, for a material with very low porosity, the boundary porosity would tend to 1, etc. It is a strange definition...
Hi Jeff,
thank you for your answer.
Conceptually I agree with you, nevertheless, speaking of common soils, I do not understand why for a very porous soil the cited equation tends to give s=s'.
Where am I wrong?
Jordan
Dear Friends,
I have some doubt about the definition of the effective stress proposed by Terzaghi and reported in the book Underground Excavation in Rock (Hoek & Brown, 1980):
s'=s-(1-nb)u
where s'=effective stress; s=total stress; u=pore pressure and nb=boundary porosity.
Evidently the formula...
Thank you Mdhshanwil,
I agree with your evaluation. My curiosity was mainly oriented to the fact that the term "reological" was involved in the correction factor: in my opinion this choice is not so logical..
Kind Regards
Hi,
it is not clear to me why it is suggested to derive the Young modulus (Ey) from the pressumeter (Menard) modulus (Em) by dividing the latter by one reological coefficient (alfa). My question arises from the fact that Em is already calculated considering only the elastic deformation occurred...
