Hi all, Rushan Gizzatullin Stefanos Papavasileiou Dennis Waterman
I have some doubts and correct me if i'm wrong.
01. I have found this equation in Plaxis 2D reference manual 2020 in page number 435. Is this equation correct ?
02. Mobilized shear strength is explained as the "radius of the Mohr stress circle" and maximum shear stress is explained as "maximum shear stress when increasing the circle (keep center constant) until the circle touch the failure envelope", then this shouldn't be the maximum shear strength (only the failure one) {definition as per in the plaxis 2D reference manual 2020). Therefore mobilized shear strength going to give maximum strength and maximum shear stress going to give the shear strength in the failure envlope (not the maximum one) when soil in the stress nearly equal to the failure mohr circle for the give c and phi soil. Then how this equation is correct [as both indicating different points in the same failure mohr cicle (considering relative shear stress is 1)]?
Thanks.
Hi,
I think you're misinterpreting. Eq. 109 gives the radius of the Mohr-Circle that touches the failure envelop, and that is the maximum shear strength. So it's not the shear stress at the point where the Mohr circle touches the failure criterion. The mobilized shear stress is the radius of the Mohr circle the current stress state. hence the relative shear stress is the ratio between the radii of the Mohr circles. See the graph below....
Kind regards,
Dennis Waterman
Dear Mr. Dennis,
Yeah i thought the perpendicular distance to the normal stress to the failure point as max shear strength. Now confusion gone, Thanks.
Hello Dennis,
Does it signify as when the soil fails, tau_max will be equal to Eq.(109).
Thank you,
Faisal
Dear Faisal,
That is a bit strange reasoning. Tau_max is the maximum possible radius of the Mohr-Circle assuming the center of the Mohr-Circle doesn't move. Hence, tau_max is always equal to Eq. 109, because that is what Eq. 109 is about, which is independent of whether the soil is currently at failure or not.
To give a comparison.Let's say somebody earns $1000 per month (=current stress state) and the company he works for told him his maximum salary (=tau_max) can be up to $3000 per month (=Eq 109). Then the quesion you ask is "is his maximum salary $3000 when he's earning the maximum salary". No, his maximum salary is $3000, irrespecively of what he earns right now.
With kind regards,