CEEN 641 - Lecture 11 - PQ Diagrams and Stress Paths

This video introduces the topic of pq diagrams and stress paths for representing stress loading of soils. Both total and effective stress paths are discussed. The significance of the stress path direction is explained.

[davidmychannel]

I'm loving your lectures. Thank you for making them available.
A point of clarification; in this lecture p' is defined as (sig1+sig3)/2, which, I believe, is the MIT definition and we in Australia tend to call s-t plots rather than p-q plots. In your CSSM lectures you have used the Cambridge definition of p', namely (sig1+sig2+sig3)/3 or (sig1+2*sig3)/3. It may be confusing to some that the slope of the fully drained stress path, for example, is 1:1 in this lecture and 1:3 in your CSSM lectures.
Great information and very well, and clearly, presented. Your students are a privileged bunch!

[teddychan]

was struggling with understanding the triaxial CU test report, and here comes this video!! Solve my confusion for years, thanks to lecturer for this marvelous course!!!

[marshmelows]

Brilliant and insightful video. The images are on point! I need to think and let my thoughts consolidate for a while so I CONNECT(in my mind) the OC behaviour in clays/dense sands to the peak behaviour in their shear strength TO the existing stress path . Thank you Professor!

[B-oc]

Very good video. I’m in a graduate geotech class and a lot of these concepts are bit rusty for me. You explain it all in a very concise and thorough way that is understandable.

[lucascruz]

I really like your lectures. Greetings from Brazil.

[hadiasadi]

wonderful lectures of CSSM, thank you Dr. Franke

[TheAncientColossus]

41:30 What do you do AFTER getting the correct stress path according to the field condition?

[khaledmohamedzahran]

Hey Dr. Kevin,

Thanks for this course. Its really useful. I can see in the playlist that we are missing from lecture 5 to lecture 10. Are they posted somewhere else?

[johnhwang]

Thank you. This lecture is really helpful to me for understanding the p-q diagram.

[aymanraouf]

Excellent video! At 19:19 I didnt quite understand why the stress path goes 45 degrees to the right for overconsolidated soils and 45 degrees to the left for normally consolidated soils

[jacksonzheng]

Thank you Professor, looking forward more videos about advanced topics to be uploaded. Greeting from Australia!

[rickycollins]

At the 19:06 time on the video you show A-bar = 0.5 as a vertical line. The notes above this state that a soil is contractive to the left and dilative to the right. The O.C. Clay curve is shown going above the K-f line between the A-bar=0.5 and the A-bar=0 lines. However, in the bottom right hand sector of the graph you indicate that if A-bar is <0, the soil is dilative. The soils are dilative starting from A-bar=0.5 or starting from A-bar = 0?

[muhamadaminalsalamat]

very winderful lecture, I highly appreciated

[sangamacharya]

very brilliant lecture, thank you so much!

[dccopa]

Hi professor, i have one question.
How does the Mohr-Coulomb failure envelope adjusts to the cases of a axial extension stress path? Are we unable to use the convencional phi and c resistance parameters that we get from the axial compression stress path?
Thank you, i really appreciate the effort that you put in your lectures. Greetings from Perú.

[alandiaz]

I have a question. If we have two UU test (or two CU with the same isotropic effective stress) in the lab, and I apply two differents path, for example, one increasing sigma 1 and sigma 3 is constant, and the another one decreasing sigma 3 and sigma 1 constant, the value of qf will be the same? I know that it will be in the Kf line, but i have the quetion because i don't know if it posible that two UU test (the same material and effective stress) can have two values of Su (kpa) due to the path. Thank You!

[aymanraouf]

Also another question @33:02 I always wondered why the stress path for LC is much longer than for AC

[wemersonsilvadias]

Hello my name is Wemerson, excellent work, very good analysis, helped me to understand a little more about Geotechnics, path of tensions, work in a Geotechnics laboratory in Brazil, specialization in geotenia, I like to be studying about it. Are you part of the LinkedIn network? Satisfaction. Congratulations.

[羅拔迪尼路-nj]

Hello Dr. Kevin,

Isn't the modified failure envelope plotting apex of max. mohr circle against center of the max mohr circle called s'-t' plot instead of p'-q'? And the p'-q' plot should be plotting the deviator stress (dia. of the circle) and the average stress.

[lampsgarden]

Hi Prof. Thank you for your video. I learn a lot from your explanation. May I know which book are you referring to in order to prepare your notes on stress path?