CEEN 341 - Lecture 24 - Lateral Earth Pressures, Part II

This continuation of Lesson 23 focuses on Rankine lateral earth pressures in cohesive soils, and Coulomb lateral earth pressures. Some discussion is also given to the analysis of lateral earth pressures on real engineering projects, including the use of mechanically stabilized earth (MSE) walls.
Learning Objectives:
1) Compute the equivalent lateral force acting on a wall using the Rankine method with a cohesive backfill
2) Explain three reasons why clay backfill behind a retaining wall is a BAD idea
3) Compute equivalent lateral force behind a wall (active and passive) using the Coulomb method
4) Explain why passive pressures are not reliably estimated using the Coulomb method

[@jayjackson5705]

This was absolutely great. Thank you for these series of lectures!

[@dhuraiathi5291]

Awaiting for your next lecture

[@mokgetoasheki1256]

Absolutely brilliant. Thank you very much

[@AsifAli-km6lj]

Great. love and respect from Pakistan

[@Javiqba]

with lot of best wishs and many many thanks.please continue these lectures.

[@bashiralasmohamed382]

nice informative lovely video,please continue for like this lec
THNK YOU

[@mrnalarcon]

Thank you so much! Greetings from Guatemala

[@ThomasBlennerhassett-mz5dj]

this was brilliant, cheers!

[@tharangadissanayaka6172]

Great lecture. Thanks!

[@XanderMande]

More videos please! And topics like Fluid Mechanics, Hydraulics and Water Resources Engineering

[@noumandar9083]

are you planning do some lecture on slop stability?
Your lecture are Great.Thanks

[@bellaroba]

Thank you for the great lecture

[@farasabyan45]

I still don't understand why the Rankine Method is the more conservative approach: as you mentioned, Rankine Theory assumes no friction occurs between the wall and soil. As such, the FBD at 11:55 shows that the shear plane in the case that friction between wall & soil is assumed to occur are more... distanced (for the lack of a better word). Meaning, more soil body needed to be supported by the wall, which in turn results in a higher LEP. This makes the Rankine Method's LEP value to be an underestimate.
Or at least that is what I perceived.
Would love to hear your feedback, cheers from Indonesia.
Edit: I understood why Rankine is the more conservative method for Active cases. What I still don't understand is why Rankine is also considered conservative for Passive cases.
Your explanation in regards that Coulomb assumed linear plane of failure, when in reality it's nonlinear; therefore Coulomb cannot be used left me with a lot of questioning. Because Rankine also assumes linear failure + no friction.

[@officehours4028]

Rankine method is more conservative for Passive lateral earth pressures in that by neglecting the friction between the wall and the soil, we reduce the amount of passive resistance generated by the soil and that we can utilize. As an engineer, when you are WANTING more resistance from the soil, then the LOWER LEP value becomes conservative. Soil does not inflict passive pressures on a retaining wall. Passive pressures are generated by the soil when something is pushing the wall into the soil.

[@hassansaleh7340]

Grat and simple explanation..
Thanks

[@safihalim3747]

Thank you very much!

[@jacksonzheng4288]

Could you please upload the advanced soil mechanics or geomechanics series?

[@shahofheartz]

Lecture no. 16 and 22 are missing so requesting to please upload them. Many Thanks

[@spirosargyros2492]

Hi, What if I am using undrained case, with cu = 30 , gamma=18kN/m2, and H=1.1m , the answer comes out negative , 1) Does this mean it is self-supported ? 2) And if have a surcharge of say 10kPa would added to the negative value ?

[@matkontakos924]

παλευουμε με youtube τωρα με τα εξ αποστασεως δυστυχως!

[@mm_channel6532]

Thank you so much Professor.

[@willrichards1454]

Hi, do you have an example problem for cohesive soils using the rankine method?

[@Stannisikorski]

Hello Dr Franke. Thank you for your excellent series of videos.
I'm min 20 you say that for passive soil pressures coulomb is overconservative .... but Rankine is underconservative. Does this mean that the only way to calculate passive soil pressures is with log-spiral?

[@officehours4028]

Not at all. Engineers often try to incorporate conservative loading estimates all the time, especially if the methods to compute them are simple and quick. If you want to compute an accurate estimate of the passive resistance, then you would need to use either the log-spiral method or a numerical method like Duncan and Chang or other similar.

[@Stannisikorski]

Thanks Dr Franke
Once again, thank you for your videos. I hope that you continue to produce more. In particular a lecture on free earth and fixed earth method would be great.

[@zinashmashie3782]

Thank you so much,

[@hassansaleh7340]

How could we find the references which you referred in this session..?

[@bSMith266]

any chance to get the CEEN644 MSE lecture?

[@brandonmensing10]

Do you have any more of these available? the PE is in 10 days and i love your lectures for review

[@aliwaqas2396]

if anyone know please reply , that how to find coulomb active and passive earth for cohesive soils , where c' > 0

[@spirosargyros2492]

Sorry 18kN/m3