Why Tunnels Don't Collapse
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- čas přidán 19. 06. 2024
- How simple reinforcement is used to prevent collapse of rock tunnels.
Tunnels play an important role in our constructed environment as passageways for mines, conveyance for utilities, and routes for transportation. Rock bolts are a type of reinforcement for stabilizing rock excavations, usually made from steel bars or bolts. This simple construction method dramatically reduces the cost of making tunnels through rock safe from collapse.
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Credit for this demonstration that was originally conceived by Tom Lang
I pinned this comment just to say thanks for watching my video, and I hope you are having a very nice summer.
i love it
Please do a video on dealing with underground water when digging tunnels, type of pumps used, methods and challenges.
+1
Thanks for another interesting video!
I really enjoy your videos, I am a graduate civil engineer and I always learn something new.
First concrete and now soil? Man this guy is totally undermining my rope business.
Jim's videos you could say he's undermining everything depending how you look at it
Jim's videos Geologists foil rope manufacturers with this ONE TRICK!
*stock photo of a bolt with a red circle and arrow*
Jim's videos Asbestos rope is still okay to make, apparently. www.asbestos.net/asbestos/products/rope/
Maybe, but on the other hand the less feasible it is the less competition you will have.
Basalt? Checks out, Brady said you could make a rope out of rock.
Great vid. I was always confused why channels like codyslab confidently walk through a ghetto mineshaft without fear of collapse
I could see this being good for a squirrel trap
THE iDubbbz watches this channel and CodysLab!?
Respect +20
iDubbbzTV2 sexydubbbz
Idubbbz you like a janissary
Who knew idubbbz liked to learn
Thank you for putting your ankles, shins and knees on the line to show us something really fascinating. Never thought this could be done.
Yeah, I was thinking he should at least wear long pants or something. I guess he had faith in his skills .
That was a very impressive demonstration that I never would have thought could possibly work!
I had my doubts.. until I saw that yellow #2 mechanical pencil in your pocket. Great demo as always!
Why did I even look in the comments? I knew you would watch these vids... Next thing you gonna tell me is that some guy has his dingus in a vise...
hey is the this old tony.
I hope he hopped off before it gave way. Easy edit though, laying in recovery from having surgically removing certain bolts from one's anatomy. It was like an engineers version of punji sticks. (Self Inflicted) See VN war.
@@bryanst.martin7134 hooooo boy... I was talking about AvE, not war crimes. That took a dark turn in only 2 months.
This video is This Old Tony approved...that alleviates all the barometric pressure I was feeling about this video. I mean, that's not how that works...but you get the point.
I would _never_ have guessed that pinning the gravel like that would work, and be load bearing! That was an impressive demonstration :D
Azy its rather similar to "mechanically stabilized earth" which he also has a video on, and concrete reinforcement using rebar, which he mentioned in this video
Unlike most of the others, this channel is related to real engineering
That was designed by a professional engineer. Don’t try that at home ;)
Impressive indeed! Instantly fell in love with this channel!
what the fk! You didnt know, how old are you? Rock is not the only one, if completly compressed, it's possible other materials. this is nothing new,
This video in particular finally explained to me how ceiling bolts work, despite visiting multiple mining museums. I think your gravel demo would be an amazing addition at the Coal Mine exhibit at Chicago's Museum of Science and Industry. You've earned my Patreon support.
We used to go to the museum a lot when we were kids. Haven't seen it in many years.
Send it to them and suggest it
I've seen these bolts used in rocky hills very close to roads. I've always wondered how some screws protected me from slidings, now I know. Great content.
You are taking about YUUUGE bolts here
If i understand that corectly, he is using bolts to make big rocks from smaller ones.
Could see the pucker factor rising as you stood on the test rig. Really cool demonstration, thank you!
bur1t0 what is the pucker factor
The Wikipedia article to this is pure gold:
"Pucker factor is a military slang phrase used to describe the level of stress and/or adrenaline response in a dangerous or crisis situation. The term refers to the tightening of the buttocks caused by extreme fear."
Yasumoth why did someone create a wikipedia article about that? lol
The wiki was created solely for this exact moment in time! xD lol
bur1t0
I would have been puckering as well!
in Syria.. when we were under siege for 5 years..we dug tunnels like this to bring in supplies and to build hospitals & shelter
But you have internet provider ? Interesting
@@RAHULSAINI-kt2kn
Sorry man... I don't get it...what does it imply that I had internet? Interesting.. You know smarty... internet is wireless... I mean it can go through walls, buildings and walls..🙄
@@RAHULSAINI-kt2kn he said "when we WERE under siege...". Brilliant man do you think he was still under siege when he posted on CZcams and therefore needed an internet provider?
@@exoressdelivers70 well siege or no siege everyone on the planet needs internet provider
@@RAHULSAINI-kt2kn let me break it down. He was under siege for five years. He had no cell phone, no Internet provider, nothing while in the tunnel. When he was set free he bought a computer, got an internet provider, and went on CZcams and posted about what happened during the siege.
The most extreme example of this bolt tensioning of rock I've seen was in the Cheyenne Mountain complex. I had the opportunity to tour the facility as an AFROTC cadet in 1983 or 84. The complex was hollowed out under the mountain and around 115,000 bolts ranging from six to twenty-five feet long were used to tension the structure as you describe here. There is also a lining of chain link fencing material to catch any chunks that might flake off. Great video.
Very cool topic. My Father worked at the copper mine near White Pine MI for about 20 years. He explained the production cycle - of which "Roof Bolting" (as they called it) was the final step prior to drilling the next series of blasting holes in the heading.
One problem with roof bolts is that if the shale chips away from above the bearing plate, the bolt is left doing nothing - it's just hanging from the anchor pin and no longer helping to support the ground around it. (Imagine removing the pieces of gravel that were in direct contact with your lower washers. It would collapse like a house of cards.)
The (now closed) mine at White Pine claimed to have pioneered the idea of using resin to hold the roof bolts in place. The hole is filled with resin and the bolt is inserted with a hardener packet and spun in order to mix it. It worked so well that they actually started suspending their conveyor belts from the roof bolts with no problems.
The equipment they used was nothing like the manual operation shown in the video though. A "roof bolter" was a large (not tall, but "thickly built") machine that used a gatling-gun-like device to drill the hole, fill it with resin, push in the bolt and hardener, and finally spin the bolt home. All done from the driver's seat of the machine. Each bolt was 16' long and they were spaced 4' apart.
biglar155 hello fellow Yooper
Howdy!
This is the cheapest and cost effective method of tunnel reinforcement.... Used all over the world...
Now underground they also put screen over the top and on the walls. Still in the older smaller workingS of mines they still use handdrills (jacklegs/ stoppers) to put in groundsupport. There is also other new rock bolts been use like split sets and grouted cables in really bad ground.
Modern technologies for ground support mine workings make it possible to attach even heavy equipment and loads to the roof of the mine
czcams.com/video/lY4N_n-n0wo/video.html
Potash Miner here! Loved the video, we use rock bolts with expanding wedges (for some reason we call them shells) every day, LOTS of them.
That's awesome! If you make a video about your mine I'd love to see it.
is potash like a deep potato byproduct?
It's mineral containing potassium that is used industrially and as a fertilizer. The name comes from the old way it was made before we started mining it. Literally "Pot Ash". They'd burn plants & trees and extract the potassium minerals from the ash by leaching them with water.
Elizabeth Greene wow, thanks man
Let me guess...Saskatchewan?
6:20 This man is going above and beyond just to show us how important and practical engineering really is. Show him some love 💗
Even though he literally just explained it my brain doesn't want to accept what I'm seeing
Damnn standing on that gravel demo was hella dangerous.. those 8" bolts would have become blunted spears to your leg if the thing collapsed. Glad ur okay
Ali Syed I know! I was saying this too, especially when it started to bending I was like “this guy is gonna die”
He’s too cool to use an antiquated adverb like very, so he says hella. I’ll bet he has friends too.
Dont you think he tried push down on it abit off camera in order to test it. My guess he did. Hard to be engineer and stupid at same time, but yea it happens. But then its overconfedence imho :)
The bolts appeared too close together for his foot to slip through to the bottom if the rocks gave way. If the rock's gave way he would have been just standing up on the bolts.
@@exoressdelivers70 I think you miss the point he took the bottom off. His weight was totally supported by the rock and the bolts tentioning the rock.
"Tunnels Don't Collapse, But Sometimes They Do!" -Practical Engineering
the disclamer, everybody needs it. its formal
Factual Engineering.
Astrology in a nutshell
i would never have thought that gravel could be made to support the weight of a man just by putting bolts through it...
i think the demonstration was too quick and may be a little misleading.
what should really matter is the ratio of the average gravel size vs the gap between bolts, and on top of that, the widths of the washers used and how much compressive force they could exert. that said, it still seems completely possible for any section to sport an inconvenient faultline and just shear off with minimal pressure. the lateral compressive forces needs to work with irregularly spaced gravel of sufficient size and with sufficient friction gripping each particle for the whole thing to act as one load-bearing floor.
in one word, the whole thing is... precarious.
Yeah, you'd be amazed at how strong friction is. Even in some houses, friction is the only thing holding all the beams together.
or maybe he swap out the wood plate for a thicker one, just to be safe. and the demo is purely for the dramatic.
Let me guess you a wear a face mask
@@alveolate its just a demonstration
These videos are so helpful. I'm currently studying a master's degree in Geotechnical Engineering and your videos on soils and rocks are super helpful and intuitive. Please don't ever stop making videos bro.
Im 6 months on the job as a geohazard mitigation technician for a Colorado based geotechnical company, GSI if you've heard of us. We do a lot of soil nails and shotcrete walls for public infrastructure around the country. On an emergency landslide job outside of Salem. Your videos are very interesting and very helpful understanding this line of work I cherish deeply. You should do one about micro-piles, high tension mesh, and shotcrete, I feel that they would make interesting and helpful videos for myself and the general public. Thanks and keep up the great work!
Grady is starting to become like a V-Sauce of engineering to me
rip vsauce.
press f for vsauce
only civil
Not really a compliment though
@Jai Rey Blasphemy!
"Safety is #1 priority in civil engineering" (c) man standing on a bridge made of gravel
I'm not an engineer, and from my point of view, it's an amazing demonstration!
Public safety*
I saw a man standing on a bunch of spears waiting to turn him into a pin cushion.
He is practicing what he preach.
@@MarkProffitt I saw that too - man this guy does not half appreciate his luck that he can still walk....
You'll probably never read this comment of mine, but in case you do: thank you, thank you for creating such quality content and sharing it on CZcams. I really enjoy learning with your channel.
I've watched this video several times, as well as a lot of your other videos. I typically only watch videos that are interesting and science based. The way the subject is presented has a huge impact on how easy and enjoyable a video is to watch. You do an amazing job. I would have to say that in terms of learning and ease of understanding, you have one of the best science based channels on CZcams.
Very interesting...Thank you for sharing.
A video on pumping concrete underwater as in large bridge footings in a river or sea, would be interesting.
@ practical engineering, yes please one of these videos will be nice!
yes please I always wondered how they do that
great idea. would like to see how that works.
Yes Practical Engineering it is a really good topic for civil engineers like us....
Yes!!!
I would watch these videos, no matter the length. But i would really prefer longer! :)
Exactly the thought I had after "Let me know what you think" - I would very much prefer longer discussion of these topics.
Alaric Balthi yes. Longer mashroom for every man
Yes please go deeper
Yes, more detailed and maybe with some equations and theoretical background
We need to go deeper!
I really wish I had seen these vids when I was a teenager! ( I wish ALOT of things had existed back then! ]
[Different topic-sorry!]
'Engineering' was never presented as interesting and understandable as this!
I very well may have chosen a completely different path in life!
Thanks for sharing, and educating!
I grew up in Goderich, home of the world's largest salt mine, while I didn't know very many miners as a child that changed a lot as a grew up. I've had several friends who've worked in the mine, and some of my extended family as well. Some of the scariest stories I've heard from in the mine were about rock bolts "blowing".
Thank you Grady, for showing me how wrong I was.
As an electrical/electronics engineer, I used to subconsiously (and very erroneously) "look down" on the "lesser engineering" field of civil engineering. Then I found this channel. Thanks for your excellent content, straightforward presentation, interesting demonstrations, and all around excitement for engineering!
I never looked down on the subject but I have found that it attracts a noticable proportion of incompetent engineers that would be washed out of other fields but manage to slip by in city jobs where nobody in administration has the background to notice the incompetence and long established highly conservative plug and chug building code hides otherwise obviously fire-able offenses. Meanwhile the local builders and city maint crews are pulling their hair out about this damned fool trying to drain water uphill or needlessly increasing costs almost as much as the cost of a lawyer to file a lawsuit [but never quite enough to make business sense].
We all look down on civil engineering m8 😂😂😂
If its done well, its probably the most beautiful and important. But so often it's practiced incorrectly.
@@Prometheus7272 everyone shits on the civvies we're used to it... until the infrastructure collapses in the next 30-50 years then suddenly everyone wants to be our feiend
I went to school as a mechanical and after a few years in automation found myself in the civil field... It's far more interesting and more complex than I thought it would be. I'd definitely encourage engineers of other fields to take a look around, and find a niche you want to learn about in the civil field. You might find yourself more interested than you thought.
So essentially it holds itself up
That is engineering genius
hmm these molecular bonds seem too weak, lets replace them with bolts xD
Wasn’t expecting those little washers to hold the rocks in place being spaced out so far! Ya killed this video 👍
R.I.P this video 😪
@@Realizinq 2i32
Keep on blowing my mind, please. That gravel table is a sort of magic I haven't encountered since childhood. Damn you're good!
Your rock bolts demonstration reminded me of Wile E Coyote where he starts jumping up and down on it until it collapses beneath him. 😄
i feel like every video should end on him jumping up and down on something ill-advised. xD
@Practical Engineering
Wile E. Coyote neglected to use roof bolts. He should have ordered some safety equipment or PPE from Acme.
That\s an awesome demo! I wonder how far you could span using only reinforced gravel...
Honnestly at 6:31 he should have kept on jumping until it fails.
I'm not sure he would have appreciated falling two feet onto a steel bolt XD
MULTIPLE steel bolts xD
In real world situation, they fix the thing with concrete before moving ahead. I really thought he was going to fix it with little concrete and then jump onto it.
It also demonstrates why things do collapse... more and more parts fall off and then the whole system collapses spontaneously. As far as i understoof mining safety actually tries to break off as many loose parts as possible until only the densely packed rest is there, which is then reinforced.
Every time I watch one of your videos Im blown away by the quality. Thank you for what you do!
Mining Engineer here - interesting to see this put into practice. It's also interesting that this theory also applies similarly to how you can reinforce open slopes too. Stereonets are also important tools in this practice too.
When you fastened those bolts, I was like, 'That's pretty much useless"
Until you stood on it !
I enjoyed learning about tensile strength. Good meeting you the other day Grady.
Bridge! You too man.
Isn't it awesome how Grady makes you excited for themes we've already studied but never had the minimum interest for? Salutes from Brazil, you're a great engineer!
opa
Thanks for the great demo! I always appreciate a relatively simple way of showing some basic engineering/physics concepts.
I think I have found one of the best channels on CZcams by far as a civil engineer, respect to you sir for taking the time to demonstrate those experiments. I can imagine how tough is it to make those videos.
fantastic video bro, also love how you handled the sponsor, so classy
I've seen this dollar shave club adds in so many different videos and always just skipped them. But this time I watched and it actually sounds like a good deal...
flooblet hey i used to play rotmg
@Tom Cheapest shave is buying a shavette + double edged blades in bulk on ebay, then break the blades in half. Even cheaper is buying clippers and growing a beard. But it's not always about cost, sometimes it's about convenience.
That floating gravel was like magic to me. Great video!
I admire you at the highest possible level. Amazing information and, more importantly, absolutely top-shelf mastery of communicating with your audience.
Excellent example of how loose rock/joints in tunnel ceilings are “Stitched together!”. Even though gravel has a much smaller particle size than the actual rock in a tunnel ceiling, this extremely simple example was able to demonstrate just how effectively the Rock Bolts could help support slightly loose rock layers of a tunnels ceiling!!!! Every time I watch your videos I always learn something new even about something that I might have limited knowledge about!!!!!
As always, love your physical demonstrations. Great video.
Your videos are fantastic. When my kid wants to watch some garbage, I say: Hey, lets go watch something we can learn from, lets go to Practical Engineering!
Should let him watch AvE
@@13anomalous16 very informative, but the language can get a bit colourful.
@@Nathanation88 This Old Tony is a good alternative, even brings his own kids on the channel from time to time.
Let your kids be kids, forcing a topic down a kids throat is what permanently turns them away from it.
@@IntelTV LOL, My kid wants to watch his videos, that's my point. (It's a joke between us). Because he is a curious kid and that's all I want from him other than good health. Plus watching "garbage" has nothing to do with being a kid LOL. Garbage is the same for adults or kids and unfortunately we can all get hooked up upon it. But this topic can be discussed at infinitum as it depends upon one's definition to some extent of what "garbage" might mean.
Best demonstration on your channel until now. And great that you show your construction in detail and length!
Your channel is full of informative materials over broad topics with supporting demonstrations. As a roboticist, I never thought civil engineering is this much fun. I look forward to more! Thanks
Your practical experiments are awesome as usual. Thanks a lot
This is one of the best simple presentations of what rock bolts actually do that I have seen. I was really surprised at how well the gravel rock bolt set-up worked! Love your stuff Grady! I've considered starting my own engineering education channel, and you are one of my main inspirations for doing so.
Awesome video! I freaking love this type of video explaining the steps in how practical engineering works
Always nice to see your videos G
Get up to Austin soon, will ya?
I love the expression on your face when standing on your table. Great demonstration!
bEING INVOLVED IN CIVIL ENGINEERING AND LAND SURVEYING THE PAST 40 YEARS I HAVE REALLY ENJOYED YOUR SHORT INFORMATIVE TO THE POINT VIDEOS. THEY ARE NOT TO LONG AND THEY COVER JUST WHAT YOU SAY THEY ARE. KEEP UP THE GOOD WORK. ANOTHER YOU TUBER THAT IS A GOOD ONE. KUDOS TO YOU ! JIM
This is so fascinating and you deserved more sub for this kind of content. Keep up the good work
My father who was a gold miner and use rock bolt, the funny thing is he was so used of it on the clear night sky he call the stars rock bolt cause they shine with the head light or hat light I should say !
"Can't make a soil rope" sounds like a challenge to me
Maybe you can make the rock rope first, as warm-up. 😊
Where is MythBusters when you need them. 😁
Just wanted to thank you for this demo. I've been doing this experiment with high school students to get them interested in mining engineering and it's been a huge success (uni student myself promoting my field). Everyone is always amazed and they love taking photos standing on the reinforced rubble once the board is removed.
Love your videos. I'm a chartered engineer with 20+ years of experience, and I'm still learning heaps from you. I've recommended you to all our graduates.
I've always imagined gravel as a slushy rock and now I'm just dumbfounded.
Gee thanks minecraft!
My God!! Finally answered my 20 year question, "how is that possible!" Keep it up!
Great to see some more technics of tunnel making, nice example very interesting.
Keep it that way 🙂
_Mind BLOWN._
I have seen pictures and some videos of underground excavations with bolts, but I had NO IDEA this is how they worked.
I've always been more interested in transportation as a subsection of civil engineering, but your videos make me reconsider my course choices! Great stuff.
William Gates-Crease Eh don't tunnels fall under transportation?
Feynstein 100 In a general sense, yes, since they're part of transportation infrastructure. However, a transportation engineer would be the one to plan where tunnels go, and what traffic uses them, whereas a geotech or structural engineer would plan the design of the tunnel and the rock mechanics related to it.
+William Gates-Crease Oh okay. I didn't know that.
Turn it into a coffee table!
Yes, please come have an espresso on this hiking trail I installed in my living room.
Brilliant....you can see the enthusiasm and effort in building a demonstration of principles. Grady is having fun in sharing his knowledge. Thank you Grady. Another great video.
Excellent explanation of rock bolts. Thanks for the time & effort (and expense) in setting up that demo.
No one:
Me at 3 a.m : *REINFORCED ROCKS*
Nobody: cares
@@MRWDL800 does anyone know the origins of this kind of comments ? (No one / Me)
Yes!
Alexander Chohan idgaf
My sister, a fellow structural engineer, will be visiting some tunnel sites next week. Your video is most timely as bridges are her focus. I forwarded it to help her prep 😜
I absolutely love the demonstration. It so powerfully conveys the concepts taught.
I'm so impressed by the experiment. I have never imagined the supports work so well
rocks at the bottom of the earth:
under pressure
pushing down on me
pushing down on me...
Gay you are
...well, better than the rocks closer to the surface...
Is this the real life?
Is this just fantasy?
Caught in a landside,
No escape from the gravity.
[...]
Mamaaa,
Just killed a man,
Dropped a rock right on his head, closed the tunnel,
Now he's dead.
Mamaa...
(Sorry, I hope Freddy will forgive us.)
Thanks for these fantastically fascinating videos Grady. You're a credit to your discipline! I have one question I'd like to hear your opinion on. (It's kind of a big one) Do you think Terraforming will be possible/plausible/practical for future engineers?
Conor Fenlon Well, having watched a lot of Isaac Arthur, i can say that terraforming is possible, but much too costly to be practical. I mean, you could make a LOT of space habitats with the same resources.
Feynstein 100 I agree. And furthermore you could make even more Earth habitats with those resources, including terrestrial structures above or below ground with all kinds of comfort and security features to withstand climate change, loss of electrical power, even toxic air or water pollution. The idea that large numbers of us will ever be better off on some other planet is stuff for a future so distant as to be truly beyond human imagination.
+Ralph Dratman Ah yes that is true. However, we should build space habitats anyway to minimize risk. As they say, we shouldn't keep all our eggs (or in this case humans) in the same basket :)
Wow! Talk about clearly conveying concepts! You have a brilliant talent.
Its like a conveyer belt at the grocery store that brings you food for thought.. 🌬🌪
Great demonstration. Glad you didn't get hurt. My new favorite channel!
Great video! One question: Have you worked in an underground mine? Just curious. Everything presented here is on point and valid. I believe these types of videos are in demand in CZcams land. Thanks
That is the most awe-inspiring and gobsmackingly effective demonstration I've seen since you parked your car on T-shirt reinforced play sand!
love your content and I don't often compliment a video. I am a mechanical engineer and I find your videos very interesting and practical. I wish university actually taught me something practical such as this.
Always love your diagrams and customized models!
This video reminded me of the 1951 film "Ace in the Hole"
An impressive demonstration, even though we can all see you are not so thrilled 6:23
Lol... if that thing collapsed, I bet it would REALLY hurt!
I really like your videos. You dumb it down to a layman level. I had wondered how the bolts they put in tunnels actually worked. I used to go into old mines as a kid and see how they used narrow passages to support the roof instead of making wide open passages with support they made narrow passages with arch ceiling. Thanks again for doing great videos.
Thank you so much for this amazing video, it would be nice if you make more videos in detail on tunnels. Thank you
To make your rock bolt design with gravel much stronger and safer, I would recommend increasing the longitudinal friction and stress by adding a dense and lightweight metal mesh to the bottom side of your design and tightening the contact between the mesh and rock by utilizing the rock bolts and running them through the mesh. This would allow any longitudinally loose rock (aka falling gravel) to be almost immovable by the strong contact between mesh and rock and be pressurized vertically as well as horizontally. The rock bolts do a great job placing vertical pressure to the rocks but not such a good job horizontally. That’s where the mesh layer would come in handy as a safety design. 👍🏼 great job and great video!
Fyx5010 maybe add some mine straps and flash coat here as well with resin encapsulated Gr. 75 Thread Bar?
As an engineer, I would like to send my sincere gratitude for making such great videos ...
Nice job! A lot of work went into this video. Appreciated.
What a fantastic demonstration of this, it makes the idea extremely clear
What about in areas where the mountain/hill isn't rocky but clayey? Like a mountain that's made of soil and gets rains too much. You drill a hole, and the mud keeps falling, so how are tunnels made through them? In India where I live, such mountains are common, still we have tunnels.
coyoteseattle Thanks for the reply :)
Generally they use a pressurized face tunnel boring machine and install a precast concrete segmental lining as they advance.
Super 👍 useful
Really super useful. Me and a couple of other inmates are working on a project....
Beautiful demonstration. Thank you.
Your vids are great! Thus far I’ve made it thru all 18 of the ones on hydraulics.
And I love the look of “confidence” you briefly have between 6:20-6:30 lol.
Hey Grady I'd love to learn about how when drilling an oil or gas (well?) Are they able to make the drill bit turn different directions rather than just straight down?
Getting stoned and binging this channel, has been the best weekend night ive had in a while. I want to be a cival engineer now.
Very interesting stuff as always, thank you for making the video.
Very professional video! Good stuff Grady!
Sir please could you make a video difference between pre-stressed and post tension concrete .
post-tensioned concrete is prestressed concrete. Are you thinking of the difference between pre-tensioned and post-tensioned prestressed concrete?
There *is* a difference. Pre-stressed means you put the cables in tension, and pour the concrete while they are in tension, then release the tension. The reinforcing is very secure this way, and there's almost no chance of failure. Post-tension usually has sleeves, and the cables are tensioned after it's cured and held in place with steel keepers at the ends. Also, with post-tension, you get the added benefit of the parabolic curve of the sleeve helping to keep the concrete flat under design loads. However, the keepers can fail and shoot the cable out of one side. There's advantages and disadvantages to both.
the term Pre-stressed encompasses both Pre-tensioned and Post-tensioned. It refers to the stress being applied before the live loads. Pre-tensioning and post-tensioning are when you stress the cables - before the concrete is poured, or after the concrete has hardened.
True. I would add that in common practice, when someone says pre-stressed, they are referring to pre-tensioned. I misread your original reply. I read it as "Are you thinking there's a difference between pre-*stressed* and post tensioned concrete?"
Yeah, we get sloppy with terminology.
I wish you were a teacher in my college. Atleast I may have learnt something, instead of just studying for marks
As a teacher, your words demonstrate the fact that HOW EFFECTIVELY teachers teach is very important. A professor might be brilliant in his field, but that doesn’t always guarantee that he will be able to effectively teach the concepts to his students. This is why students shouldn’t give up when frustrated while learning... teaching styles matter!
Awesome video! I learned a lot and the experiment really helped pull all the concepts together.
Grady this is so great! The soil and rock comparison was perfect and the "knitting" analogy made perfect sense. Thanks for the knowledge!