Understanding why soils fail
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- เผยแพร่เมื่อ 29 ก.ย. 2024
- Soil mechanics is at the heart of any civil engineering project. Whether the project is a building, a bridge, or a road, understanding the underlain soils is of crucial importance. This video is a series of several geotechnical videos that will investigate retaining walls, shallow foundations and piles. But before we dive into these geotechnical applications it is important to understand a few basic principles about soil mechanics. This series starts by generic introduction of soil material models. Namely, the Mohr-Coulomb model which is widely used for modeling the strength of brittle materials.
Geotechnical Series Videos:
1. Understanding why soils fail ( • Understanding why soil... )
2. Understanding the Soil Mechanics of Retaining Walls ( • Understanding the soil... )
3. Geotechnical Analysis of Foundations ( • Geotechnical Analysis ... )
4. The Leading Cause of Foundation Failures ( • Residential Foundation... )
References:
[1] D. P. Coduto, M.-c. R. Yeung and W. A. Kitch, Geotechnical Engineering Principles and Practices, Pearson, 2011.
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Heck yeah! I work in retention wall design, so I'm pretty excited for this series
That's great Matthew, retaining walls are coming next (in about 2 weeks). Looking forward to your feedback and discussion on that video.
No permafrost that's really heavy, you have to dig it mix it then put it back
Great video my dude
Hello nice presentation! But i have one question. If soil is totally dry (no water in voids) shear failure occurs when friction between soil particles is smaller then shear stress in the soil, and that's obvious when you think about it, BUT, what about wet soils or soils that are in groundwater (saturated soils)? Friction now is not intuitive and what is the mechanism of failure then?
As long as the particles in the soil are in contact the friction will be there. What happens in a saturated soil is that the positive water pressure decreases the stress that holds the particles together. This is knows as the 'Terzaghi's law' of effective stress. From the total stress coming from e.g. the total weight of the overburden (the weight of the soil column, including the soil particles and the water between them) we have to subtract the pore water pressure - this resulting stress is the one that is really important. As long as it is larger than zero, there will be some positive shear strength. If the soil is not fully saturated (unsaturated) some suction may exist between the particles - this is then increasing the effective stress and so - increasing the shear strength. The Coulomb-Mohr principle saying that (the shear strength) = (the effective normal stress) * (the angle of friction) holds true for all dry, wet and saturated soils.
So if effective stress is zero or very small any vertical load on that saturated soil will cause it to fail in shear?
@@Veke96 Any HORIZONTAL load will shear it. Yes. Unless it is a fine preconsolidated soil (e.g. clay that has been loaded before more than it is now) or very angular coarse soil (sand, gravel). In these cases the shear strength may be increased (up to some effective stress) by 'cohesion' being the effect of interlocking of the grains/particles. In soils the history of loading is important...
Great explanation of soil shear strength with easy-to-understand visuals! Job well-done!
Thank you Xinbao, positive feedback from our viewers means so much!
where I study people claims that this is the thing to understand
This is wonderful. Thanks for all your work.
Thank you so much for the kind words Mister P. Comments like this always keep us motivated to do more!
Very good and clear explanation, I'm studying geotechnics right now and this video is really great. A video about the calculus of elastic and plastic deformation on triaxials would be great 🤪🤣
Keep up the good work 🙌🏼💪🏼
Hi Andrea, thanks for the comment. We are very glad you liked the video, we will keep building with more videos and increase the complexity slowly. It might be a bit early for complex stress states and plasticity yet but could come up in the future.
Just what I'm looking for, nice explanation keep up with videos of geothecnics applications!!
More to come, stay tuned and thanks for the comment!
Fascinating and so well-illustrated. You know how to appeal to intuitive understandings so as to make the videos compelling!
The animations, explanations of concepts - everything is on point! Thank you!
And thank you for taking a second to say this. It means a lot to us 🙏🙏
Very educative.....I want to get deeper understanding in Geotechnical engineering and why foundation fails
Andrew Schofield, one of the pioneers of critical state soil mechanics and cam clays recommends people not to use the term cohesion but instead use cementation
Shear resistance of a material is normally a third to a half of the the compressive resistance
The video is made in Hindi and is less understandable in English.😂
oh. wasn't the sort of soil failure i was thinking of but extremely interesting all the same
Hi Billy, this was an introductory video with broad and technical content. Stay tuned for the geotechnical applications that follow with more specific failure examples.
very good explanation. if you don't mind, What kind of program do you use for drawing ?
Hi alzou, we use a variety of software. Which drawing are you referring to?
In practice, soil would not be able to carry increasing loads, even if well co fined because of firstly the particle crushing and secondly chemical changes due to high pressure
Yup, you are absolutely right. But those types of stresses would be beyond a structural application.
Thanks for the explanation about soil mechanics! Very useful information. Keep up the good working!
Thanks Mavlonov, new soils video coming out soon, stay tuned!
How much time it takes to make 1 video
I hope you'll reply me
Hi @dilipkumarpatel481, it ranges from video to video. This one was on the low end and took about 40-50 hours. Other video can take even up to 100 hours if the topic requires a longer explanation and the animations are more complex. Thanks for the comment!
In Norway a farmer was having some kind of pit dug. The soil was piled up along the bank of a nearby river.
And a sheer slide started.
Evidently this land, some of the best farmland in Norway, is on top of a layer of clay. When it started sliding the whole layer slid taking, as I remember, about 4 whole farms with it. It is continuing sporadically.
I'm still trying to wrap my mind around that. How did that bit of soil piled up on the river bank so destabilize the whole area?
Excellent video series! My group is very appreciative. Feom time to time, we show them to our clients When we need to explain a concept that's hard for them to understand.
Thank yiu for imparting knowledge and please continue enlightening the masses.
thank you for the intuitive explanation of the soil friction angle. These videos are super helpful.
Glad it was helpful! More videos are on the way!
Thanks a lot... in just 5mn i learnt what i couldn't learn in my 4 years of engineering degree...
Great value addition Thanks Sir 🙏
So nice of you, thank you sir! Your comment is appreciated!
In the case of post pull out or lift, do you ever consider impact of vacuum created with upward movement of post?
I think you have explained the concept of soil strength well.
Good video. More on slope stability would be helpful for me.
Amazing sir
Thank You
i am a residential builder and i appreciate these informative videos.
Awesome explanation! Thank you!
Best and simplest explanations without getting bogged down with white board drawings and funny math. Thanks!
Thanks Patrick!
I was expecting to hear about the hydrostatic pressure gradient (or some equivalent for saturated soil) affecting the shear stability of a soil medium.
That will be coming up in the next videos when we go over slope stability. We felt that it was a bit too early to go too debt into stability.
Good way of explanation
That means a lot given that is coming from a Geotechnical Engineering Consultancy!
Excellent presentation
um, cause they didn't study hard enough and they didn't get any support from their parents...I am right ? what did I win ?
hahah love this, one of my favorite comments on the channel for sure! 😂
Concise, clear and knowledgeable 👌
I work as a geotechnical engineer for a large European construction company and I enjoy such short spot-on videos for in-house training purposes.
We are flattered Maxim, thank you so much for your comment! If you enjoyed this video there is a good chance you might find our video on retaining walls also entertaining!
So happy to see videos on geotechnics!
Good animation and explanation
Excellent!
Nice buddy
This channel is highly underated.
We are flattered, thank you Victor 🙏
Good job man, keep going 👍
Thanks, will do!