CE 326 Mod 12.9b Triaxial Shear Test

[@simonnguyen3606]

whoever gave this a thumbs down must be CRAZY! Being able to see a visual representation of what is happening on the graph while the test is being conducted is what makes this such an effective video. I look forward to viewing your other videos CHEERS!

[@robertplautz9722]

it is hard to find videos of this quality: clear sharp narration, easy-to-understand, detailed explanation, amazing graphical (visual) presentation. thank you so much!

[@alideep9656]

I live where the Triaxial stress is so expensive and the university never turned the device on or fully explain how things go during the test, I can't thank you enough for this outstanding explanation.

[@m3talh3ad18]

Thank you so much for your simplified and on the point explanations. I tried a lot of text books but everything was a bit complicated, for me. Your voice is clear and slides are well made.👍🏾

[@emmerydickinson8302]

A simplify yet comprehensive explanation about triaxial tests. Thanks a lot for a helpful video

[@rafiullahqallander]

Dear Professor Kitch, Thank you so much for such incredible explanation; you saved my life :)

[@taladiv3415]

Thank you yet again Prof. Kitch for using your talents to help unlucky students make sense of all the letter and figure salad !

[@AroundRavikant]

extremely thankful to u for this video... i was confused from many days about this topic.

[@muhammedajmal715]

It was an excellent presentation with to the point explanation with figures. Easy to understand the concept. Thank u soo much professor

[@meaghanmacquarrie3755]

Thank you for this video. You have helped me develop a better understand on concepts I have struggled to learn. This is one of the best videos I have come across. I especially liked the corresponding mohr-circle diagram to triaxial type test! Thank you!!!

[@ГеоргийЛохматиков]

Thanks for your video! Its clearly observed misbeliefs of foreign geotechnical engineering based on outdated Therzagi's theory. Very helpful for my students.

[@gh5030]

That’s what happens when we mix the hight knowledge and super teaching ability, very very useful, much better than my text book.. thank you so much

[@39shobhit]

very nice and effective presentation .... all the concept that you have told can be easily understood ......thank you for this great work ....

[@VikashKumar-vl4hv]

excellent video, one of the best study tutorial video i have gone through. thanks a lot sir

[@ShashiKumar-yv7wf]

Thank u very much for this video. One of the best video I have ever seen. All my concept about this topic is clear now.

[@debangsu3181]

SUCH A SIMPLE AND TO THE POINT EXPLANATION OF CU,UU,CD TESTS

[@rhushitparmar5939]

Thank you so much. It's very conceptual and cleared my all doubts.

[@contacttaimur]

Many thanks. This video was really helpful. And its like The Godfather, I watched it 3 times and still enjoyed it.

[@riccardocandeago4699]

Thank you! This will help me with my geotechnics exam :)

[@SauravKumar-ic4ly]

Thank you so much for this video, such an amazing way of explanation.

[@mounika501]

Outstanding explaintion I'm really happy with thus vedio nd I learn very much about this topic

[@gildanibarcentti5954]

Excellent explanation! Love your ending :)

[@zs6511]

Best video for triaxial shear test.

[@JamanMonir]

absolutely great tutorial or lecture. helpful for anyone who was in doubt like me. Thanks by the way

[@n4tsumi]

Really helpful for confused engineering student like me! thank you!

[@omkardhamane269]

Thank you so much for this video....I was very confused about this topic

[@ferfixer2]

Thanks!! This video helped me a lot. However I do not understand why is in consolidated and undrained triaxial test the pore pressure negative. Could you tell me?

[@introductiontogeotechnical4976]

ferfixer2 When soils are sheared under drained conditions they can either contract (decrease in volume) if they are relatively loose or dilate (increase in volume) if the are relatively dense. This happens because soils are made up of individual particles that roll and slide over each other during shearing. If the soils are saturated and sheared under undrained conditions there cannot be any volume change (contraction or dilation) because both the soil and water are incompressible (relatively speaking). So instead of volume change during shear, there is a different reaction--change in pore pressure. Relatively loose soils generate positive pore pressure during shear because the soil wants to compress and push out some water. Relatively dense soils generate negative pore pressure during shear because the soils wants to dilate and draw water in. Hope that helps. I have some nice ideas for videos on this, but they won't be done for some time.

[@adriananazcocampoverde1918]

Introduction to Geotechnial Engineering Excelent!

[@krishnakadiyam2864]

@@introductiontogeotechnical4976 best reply of my utube life

[@scientificresearch1400]

@@introductiontogeotechnical4976 waiting sir

[@introductiontogeotechnical4976]

Vishabjeet Singh Rajput please see this webcast for an explanation dilation and contraction during shear. kzbin.info/www/bejne/jnSygYGDec2Loa8

[@aveenaaspaudel8040]

In 13:55, you said that effective stress is greater than total stress, but in other books and videos, pore water is positive and it gets subtracted from total stress.

[@OHamdi]

Was looking for this. The circles he draw for effective stress cant be greater than total stress

[@shahriarislam7134]

Wishing to see more of these helpful videos

[@sarahgibson492]

Excellent, concise and clear!

[@sayantanmunshi9969]

Detailed presentation should be like this. Thank You Sir

[@adamperez1993]

At 14:00 during the CU test why was the effective stress circle shifted to the right? Isn't this a positive pore water pressure? Negative would be a suction. Sigma' = Sigma - u

[@oussamaali8393]

+Adam Perez review terzaghi postulate

[@sanngo8002]

I think the pore pressure is positive, but the change in pore presssure delta u is negative.

[@nikossidiropoulos5627]

you actually wrote it Sigma' = Sigma - u, only that u is negative, so -(-u)=+u

[@leung77]

Dear Professor Kitch, may I raise out a question on the CU test that why a negative pore water developed such that effective stress is larger than the total stress, shifting the Mohr Circle to the right? Thank you

[@introductiontogeotechnical4976]

Dense or overconsolidated soils tend to dilate during shear, that is increase in volume. In this case, we’re shearing under undrained conditions, e.g. no volume change allowed. Therefore, instead of dilating, the soil responds by generating a negative excess pore pressure.

[@James-oc3fr]

Thanks for video. it is really helpful for me to understand. good explanation. great

[@mohamadoubanhoro9188]

great video on triaxial shear test

[@luongtuananh1220]

very good demostration thank you a lot

[@eatedalalqusaireen3664]

Very helpful. Could you give practical examples when to use each test??????????

[@rawalali5182]

thank you sir . it helped me clear my concept quite efficiently.

[@caebc]

The Best video

[@dragonborndovahkiin6523]

Yes

[@parasbhatia6999]

very nice video . thank you very much for such a quality content.

[@jacksonzheng4288]

Why do we have a negative pore pressure during the CU test??

[@JJw-l8f]

It's depends on soil is normal consoilidated clay or over consoilidated clay. Each has different tendency of volume strain which lead to +or- pore pressure.

[@walidtlili7415]

I still dont get it

[@moipu8868]

I reckon if the sample is OC/very stiff it would dilate during the first part of shearing and so the volume of the sample would increase. The increase in volume would cause -(ive) pore pressure ...silly

[@saminyead1233]

Basically, pore pressure generally seeks to decrease the effective stress of soil. Thus, if pore pressure increases the effective stress, it means the pore pressure is negative. As to why this can happen, you have to keep in mind that pore pressure usually seeks to decrease effective stress only if the soil is saturated. In other words, the pore pressure is negative only if the soil is saturated. Here, during the CU test, since we drained the soil sample in the consolidation phase, a significant amount of water has left the soil sample and thus it is no more saturated. In unsaturated conditions, the pore pressure is negative. This is the reason for the negative pore pressure. If you want to know why pore pressure is negative during unsaturated condition, then I suggest you visit this link - environment.uwe.ac.uk/geocal/SoilMech/water/water.htm Hopefully, you'll get your answer. :)

[@gtrslayer1]

Thank you! Extremely helpful.

[@dr_greg_mouse4125]

This is a great video indeed. Thanks.

[@tonyk2038]

Thank you for this video!

[@frozentesla7771]

this video saves my life thanks Godbless

[@davidliu2328]

thank you for being so awesome!!!!

[@9076173238]

Amazing explanation!

[@xavierariverahernandez5550]

Good Video. Thank you! The last part was the best!

[@cr_love_passion]

In Consolidated-Undrained Test, Why negative pore pressure is developed ? Why not positive pore pressure ?

[@dimasrizaldy2901]

sorry sir, but shouldnt the normal stress is bigger than the effectice stress just bcs the delta u is not negative?

[@muhammaduneebalam5029]

Love you sir!

[@ahmedobidat1743]

I read in your book (Foundation Design Principles and Practices 3rd edition) this statement. In general su (phi = 0) increases with depth because the lower portions of the stratum have been consolidated to correspondingly greater loads, and thus have a higher shear strength. Would you please explain why does consolidation increase shear strength? Thank you so much!

[@introductiontogeotechnical4976]

Consolidation increases the density and decreases its void ratio. This will both stiffen and increase the strength of the soil.

[@ahmedobidat1743]

Your the man! Thanks a lot!

[@bmansan]

Excellent explanation

[@superbananavoltex]

Hi, thanks for the informative video, I learnt a lot! However, there's something that has been bugging me. From what I understand on my notes and also from my search, effective stress = total stress - pore pressure. But from your video on the part of CU, effective stress = total stress + pore pressure? Do correct me if my understanding on the video is wrong.

[@sagarsrsshah]

Cleared my doubts. Thanks!

[@madhureddyindian9715]

Sir I love your explanation. I greatly appreciate your work. Love from India.

[@shahzadikhan8356]

best explanation ever

[@alxms10]

I have a question: in the last test (CU), first you allow water to drain slowly to measure sigma_3, and then close valve to measure excess water pressure, how did the gauge measure water pressure? Did you fill the sample with water again after drainage and before closing valve?

[@nikossidiropoulos5627]

13:21 - CU test, should the σ3 value at the consolidation stage be effective consolidated stress like in CD test at 11:53?

[@george6709]

no but you can obtain the effective stress by subtracting the pore pressure from the gauge

[@rajatkushwaha4296]

for consolidated undrained test of normally consolidated clays in my textbook ....effective stress mohr circle is depicted by solid lines while total stress circles are by dashed lines also total stress circles are shifting right to the effective stress circles .....i.e effective stress are less than corresponding total stresses......i am confused.

[@hirasingh4495]

Amazing video!

[@pedrokaluf4189]

best video ever!! nice job

[@matijagrivic3810]

At the CU test 13:50 ....Shouldn't you subtract pore pressure from total stresses rather than add them,since effective stress equals total stress minus pore pressure?

[@introductiontogeotechnical4976]

We did subtract the pore pressure from the effective stress. In this case the shear induced excess pore pressure was negative (a dilative soil), so subtracting a negative stress added to increase the totals stress.

[@CuteCookie96]

That was very helpful, THANK YOU!

[@DEEPAKKUMAR-lt6iy]

Very good videos I am happy with this

[@nafiaykut6556]

I want to ask a question.I have calculated Fs from Michalowski’s (2002) 1.875 and I have calculated Fs=2.047 from slope stability program.What is the reason of this difference?

[@chrisronald2856]

really nice video

[@yektakaya4635]

does consolidating the soil mean the confining pressures are increased ? Because it says the soil is consolidated before being compressed

[@yinminthann4822]

thank you Prof.

[@nimeshmakwana56]

Suparb explanation...👌👌

[@SunitaDevi-sv2bo]

Thank you sir

[@hikuuuuuuu]

Thank you so much!!!!

[@williamt.szeibert8699]

If CD takes longer to conduct than the CU, and gives you the same parameters as CU, when would you use a CD test over a CU test?

[@introductiontogeotechnical4976]

Precisely why CD tests are seldom done.

[@MehsamTanzimKhan]

very good explanation! !

[@sevvalkursun16]

Thank you so much hocammmmm

[@halilibrahimsahin4639]

Thanks from Turkey

[@introductiontogeotechnical4976]

You’re welcome.

[@chimoscreations9103]

amazing video

[@bhandaribishnuhari7223]

everything is clear sir ..

[@228MOHAMED]

God Bless you

[@lulukobe8nba]

thx a lot Prof

[@krishanundas5497]

really nice presentation...

[@parveshshukla3615]

its very helpful video

[@joonpark3512]

For tests where the valve is open, do the pore pressure hit zero?

[@waseembhat2657]

great video

[@khantahsinazad4250]

You are excellent

[@dann5480]

god bless the Americans!

[@fabienwang5706]

worth more than my undergraduate degree lol, imaging being a geotech student and studying all the important stuff on YT......, says a lot about university education..

[@kandikatlasrinivas1571]

Sir i confused why should we study critical state soil mechanics

[@victimboy7765]

Excellent! That is all I can say!

[@shalukafernando6910]

In the CU test (14.02) the Mohr Circle given by the total stress. Then the pore water pressure added and create the new mohr circle of effective stress. why is that? that Effective Mohr Circle should be left side to the Total Stress Mohr Circle? Effective stress = Total stress - pore water pressure ?

[@LUKASFELIXXIONG]

Shaluka Fernando the consolidated dense soil wants to dilate (expand), which will absorb water resulting in a negative pore water pressure.

[@arking1208]

Thanks a lot, good lecture

[@gabrielseabra7590]

How do you know when the failure occurs, exactly? Thank you for the lesson, by the way. Excelent content!

[@mattclinton5351]

Good question. I think there’s peak and residual sigma 1 stresses during shearing. Deciding which one to use will depend on the project. I find John Atkinson’s “Mechanics of Soils and Foundations” book extremely informative

[@slowly5092]

What is the highest triaxiality factor that can happen. Since triaxiality factor is ratio of mean stress, to the von Mises equivalent stress, what does it mean if triaxiality is 0.5, or 1, or 1.2? What does that mean for material? is it possible that TF is larger than 1?

[@srimanideepallavarapu925]

excellent

[@CivilConqueror]

In CU test there will be effective stress in confining stage as per my imagination and concepts but hear taken total stress in confining stage

[@baltichannelskardu]

Nice

[@mohituniyal4839]

thanx a lot.... great lecture

[@hoggerz]

The Mohr's Circle for the Consolidated-Undrained test is incorrect. Effective stress is total stress minus pore water pressure (σ' = σ - ∆u). σ' would be less than σ, the dotted circle should shift left, not right.

[@willliamkitch2967]

The Mohr’s circles are correct. This soil in the animation is generating negative excess pore pressure during shear so the effective stress increases. Negative excess pore pressure occurs when overconsolidated clay or dense sand is sheared under undrained conditions.

[@krissiregar8083]

when explaining CU test, you must know the consolidation state of the soil speciment. just like +Adam Perez asked and +Riad L. explained. when the clay soil is NC, the effective stress envelope moves to left and if the clay soil is OC, the effective stress envelope moves to right

[@ahmedobidat1743]

For the first consolidation phase, I think the Professor means primary consolidation settlement because the load is being increased. Does anyone agree?

[@introductiontogeotechnical4976]

It could be primary consolidation or secondary compression. The source of the consolidation is not important for this discussion of shear strength.