Mini-lecture 11.5 - Mohr-Coulomb criterion II, part of the topic Brittle deformation and faulting in the Geodynamics course at the University of Helsinki. Lecture slides: matskut.helsinki.fi/handle/12...
Thanks a lot, teacher David! Your objective explanation helped me very much. Are you from Finland? I haven't notice any different accent that I, as a Brazilian guy, couldn't understand. Greetings from Curitiba!
Hi David, thanks for the wonderful lectures, pls what's the difference between 'pore fluid pressure' and 'pore pressure'? The question I'm trying to solve goes like this. For a rock the coulomb failure criterion is given by σs = 150 + 0.466σ. The stress state for the rock is given by σ1 800MPa, σ3 = 200MPa, How much pore fluid pressure do you need for shear failure to occur without pore pressure, how much do you have to increase the diffrential stress (at given σ3) for shear failure to occur? Use a mohr scale construction for solving the problem and show your work Thanks
Hi. I'm glad you found the lectures helpful! Pore pressure and pore fluid pressure are the same thing. The basic idea is that fluids filling the pore space in rock and under hydrostatic (or even greater than hydrostatic) pressure will lower the stress needed for failure to occur. An alternative way to have failure would be to increase the differential stress without a contribution from pore fluid pressure. It seems the question you're working on is asking you to do both calculations. Good luck!
Stüwe K., 2007. Geodynamics of the Lithosphere. Springer, 498 pages. You can download a copy of the e-book from the authors website at wegener.uni-graz.at/publication/books/geodyn2nd/.
