I'm a homeowner and retired software engineer with nothing to do with mechanical engineering. HOWEVER I am putting in a patio and I'm compacting the soil/gravel base/sand. I stumbled onto your video and I'm fascinated. The proctor test and compaction curve help me understand exactly what's going on under my feet. I had no idea that if you compact soil too much it can become viscous. Good to know, though I doubt if I'd be able to get to that point! Thanks for the great video. Much more fun watching it than going outside and working on the patio!
Internet is a great tool. Thank you very much sir, watching all your lectures on soil mechanics as we are getting closer to the end of the sememster and they really help a lot! :)
Great videos! I am a geologist learning soil mechanics for my job at a geotechnical company, your videos are some of the best content I can find online by a long shot! One question, you mention that the best water content is -1% and +3% of optimum, why is the error on the wet side greater if the increase in moisture makes the soils less strong and give potential for swelling and pumping?
Dr. Franke - thank you for the content. How are the results of the modified proctor actually applied in the field, for situations where the soil won't be disturbed, say at the base of a spread footing. Suppose the optimum moisture is determined, how is a contractor actually increasing or decreasing the moisture % in the field, and to what depth? The layer beneath said depth won't be tested or compacted, isn't the compaction only as good as that beneath layer?
Really well explained. The theory reminded me about the soil mechanics lectures around 1985 at Aston University and later at City University, London. Musood Karim.
Being a field engineer, my question would be HOW CAN WE SAY IF THE MOISTURE IS INSIDE THE SPEC LIMITS say, +-3% of OMC by feel before giving the Green sign to the earthwork contractor? As per the experience, they say, Nuke doesn't reflect the exact moisture. Therefore, need to feel the moisture and relay to the contractor. Also, the dummy test is performed. However, by the time of completion of the dummy test, the contractor would have placed the layer. Your expertise shall be highly appreciated. Sumit
In 7:06 you say we can get the unit weight by weighing the moist sample and dividing it by the known volume (volume of the container), then we dry it in the oven and can obtain the dry unit weight by weighing it and then dividing by the same volume. Then using the following formula, we can calculate the moisture content: moisture content = (moist unit weight - dry unit weight)/dry unit weight. I don't see where the specific gravity of soil solids (Gs) comes into play?
I watched this because I needed some knowledge for a field compaction project. I learned a lot! thank you! But professor! that voice of yours put me to sleep like 55.5% of the way into the lecture. Were you falling asleep yourself? I am using exclamation points to wake you up! I hope you are using tone changes in future classrooms. LOL. Made you chuckle but seriously change it up. (I really did learn a lot.)
Is it true that Cohesive soils compacted on the wet of optimum in the preparation of soil liner would result in higher strength than soil compacted on the dry of optimum.?
From what I learned, cohesive soil becomes more compacted as the voids are removed from the soil. So to answer your question, which side of optimum removes the voids? Sounds like wet of optimum removes more voids, because it pushes water into the void space and thereby compacts the soil, improving its density. Maybe the experts can verify? I am a newbie.
How do we know how much energy the compaction equipment gives? Won't that change how much water content is needed. The more compaction energy is provided the less water is needed to optimal compaction, but usually there's only one optimum moisture content, implying there should also be given a optimum compaction energy, no?
Nuclear densimeter should work together with a sand cone test. 1 sand cone test can help you to check if nuclear densimeter is good to go. It is cheaper spent 20 minutes to check 1 point with nuclear and sand cone test than watching a future problems trusting 100% with the nuclear densimeter.
In 5:41 you compute the energy incorrectly because you have to multiply by gravity g because 5.5 lb is mass, not weight. I am just pointing this out so viewers don't get confused. Engineering is tough as is.
That is not correct. The unit of pounds is computed as slugs (ie., mass) multiplied by the acceleration of gravity. In the context of the example given, the unit of pounds is a force.
I would humbly disagree again. Because 5.5 lb mass is equal to 2.5 kg. Also, I looked up the Standard Proctor test in a soil mechanics book and it says that the MASS of the hammer should be 5.5lb.
Sorry, but you are incorrect. You are confusing lb mass and lb force. See this article. en.m.wikipedia.org/wiki/Proctor_compaction_test, under the section “Comparison of Tests.” There is a difference between lb mass and lb force. In the energy computation, I am using lb force. The hammer weighs 5.5 lb force. If you want to convert that to lb mass, then you need to divide the 5.5 lb by gravity, which will give you lb mass, or slugs. If you multiply the 5.5 lb by 32.2 ft/sec2, you will have double-counted gravity and significantly overestimated the energy.
Dr Franke breaks it down to pieces! He's so gifted at explaining the seemingly hard things to look so easy.I will recommend his videos anytime.
I'm a homeowner and retired software engineer with nothing to do with mechanical engineering. HOWEVER I am putting in a patio and I'm compacting the soil/gravel base/sand. I stumbled onto your video and I'm fascinated. The proctor test and compaction curve help me understand exactly what's going on under my feet. I had no idea that if you compact soil too much it can become viscous. Good to know, though I doubt if I'd be able to get to that point! Thanks for the great video. Much more fun watching it than going outside and working on the patio!
Internet is a great tool. Thank you very much sir, watching all your lectures on soil mechanics as we are getting closer to the end of the sememster and they really help a lot! :)
Great videos! I am a geologist learning soil mechanics for my job at a geotechnical company, your videos are some of the best content I can find online by a long shot!
One question, you mention that the best water content is -1% and +3% of optimum, why is the error on the wet side greater if the increase in moisture makes the soils less strong and give potential for swelling and pumping?
Recently started a position as a Field Tech and this video helped my understanding greatly. Thanks for your effort.
Really good stuff! Explained very well. This guy knows his stuff. Worth watching.
Dr. Franke - thank you for the content. How are the results of the modified proctor actually applied in the field, for situations where the soil won't be disturbed, say at the base of a spread footing. Suppose the optimum moisture is determined, how is a contractor actually increasing or decreasing the moisture % in the field, and to what depth? The layer beneath said depth won't be tested or compacted, isn't the compaction only as good as that beneath layer?
Really well explained. The theory reminded me about the soil mechanics lectures around 1985 at Aston University and later at City University, London. Musood Karim.
God bless you! Your explanation is very precise and clear! Thank you so much for posting those videos they are extremely helpful!
Being a field engineer, my question would be HOW CAN WE SAY IF THE MOISTURE IS INSIDE THE SPEC LIMITS say, +-3% of OMC by feel before giving the Green sign to the earthwork contractor? As per the experience, they say, Nuke doesn't reflect the exact moisture. Therefore, need to feel the moisture and relay to the contractor. Also, the dummy test is performed. However, by the time of completion of the dummy test, the contractor would have placed the layer.
Your expertise shall be highly appreciated.
Sumit
I believe it's more of a preparation to be done prior to the beginning of actual fieldwork
I cant thank you enough for the excellent explanation.
Thanks for very informative lecture.. I revised my old knowledge ,, Nice Job Sir..
In 7:06 you say we can get the unit weight by weighing the moist sample and dividing it by the known volume (volume of the container), then we dry it in the oven and can obtain the dry unit weight by weighing it and then dividing by the same volume. Then using the following formula, we can calculate the moisture content: moisture content = (moist unit weight - dry unit weight)/dry unit weight. I don't see where the specific gravity of soil solids (Gs) comes into play?
Modified proctor test in Brazil are 55 blows per layer(55/5) 10lbs hammer and cylinder volume 2080 g/cm³
Gentleman, Would you mind if you provide project summary so that I can discuss about these limits with my Professors?
Thank You.
Have a Good Evening.
Excellent presentation
Thank you. I just started at a geotech firm.
I watched this because I needed some knowledge for a field compaction project. I learned a lot! thank you! But professor! that voice of yours put me to sleep like 55.5% of the way into the lecture. Were you falling asleep yourself? I am using exclamation points to wake you up! I hope you are using tone changes in future classrooms. LOL. Made you chuckle but seriously change it up. (I really did learn a lot.)
Is there any correlation between the Proctor test and the CRB test?
How do contractors know how much moisture to add to base materials to achieve optimum compaction ?
Is it true that Cohesive soils compacted on the wet of optimum in the preparation of soil liner would result in higher strength than soil compacted on the dry of optimum.?
From what I learned, cohesive soil becomes more compacted as the voids are removed from the soil. So to answer your question, which side of optimum removes the voids? Sounds like wet of optimum removes more voids, because it pushes water into the void space and thereby compacts the soil, improving its density. Maybe the experts can verify? I am a newbie.
How do the contractor add proper amount of water and equal energy to get the maximum dry density?
How do we know how much energy the compaction equipment gives? Won't that change how much water content is needed. The more compaction energy is provided the less water is needed to optimal compaction, but usually there's only one optimum moisture content, implying there should also be given a optimum compaction energy, no?
You fell asleep in the classroom. He explained that.
you explain in such a nice way. can't we use core cutter method to find dry density?
Well explained and to the point, I LIKE IT!!
Do you know how we can determine the specific gravity of a mixed soil such as select fill 60/40?
This is very helpful. Thank you.
Very good!
Thanks!
Nuclear densimeter should work together with a sand cone test. 1 sand cone test can help you to check if nuclear densimeter is good to go. It is cheaper spent 20 minutes to check 1 point with nuclear and sand cone test than watching a future problems trusting 100% with the nuclear densimeter.
I wish that you include special compaction techniques including vibroflotation, dynamic compaction and blasting, tnx sir ^_^
Thank you very much sir. God bless you.
Excellent mate
THANK YOU.
I wonder high density more than necessary reduces the productivity.
Sir , Then what's the rectification for this over compaction.
As he said, we'll have to remove the soil (unfill) and redo the process (refill)
Thank you very much!
I am watching this video to pass my GE(A)...examination...
In 5:41 you compute the energy incorrectly because you have to multiply by gravity g because 5.5 lb is mass, not weight. I am just pointing this out so viewers don't get confused. Engineering is tough as is.
That is not correct. The unit of pounds is computed as slugs (ie., mass) multiplied by the acceleration of gravity. In the context of the example given, the unit of pounds is a force.
I would humbly disagree again. Because 5.5 lb mass is equal to 2.5 kg. Also, I looked up the Standard Proctor test in a soil mechanics book and it says that the MASS of the hammer should be 5.5lb.
Sorry, but you are incorrect. You are confusing lb mass and lb force. See this article. en.m.wikipedia.org/wiki/Proctor_compaction_test, under the section “Comparison of Tests.”
There is a difference between lb mass and lb force. In the energy computation, I am using lb force. The hammer weighs 5.5 lb force. If you want to convert that to lb mass, then you need to divide the 5.5 lb by gravity, which will give you lb mass, or slugs. If you multiply the 5.5 lb by 32.2 ft/sec2, you will have double-counted gravity and significantly overestimated the energy.
Here is another nice article that explains the unit of pounds. hyperphysics.phy-astr.gsu.edu/hbase/Mechanics/slug.html
you are right. I am sorry for all the confusion. Thank you for the very useful links.
You’re amazing!
Finally seeing what the internet meant to be used for