Why Retaining Walls Collapse

One of the most important (and innocuous) parts of the constructed environment.
Look around and you’ll see retaining walls everywhere holding back slopes so we all have a little more space in our constructed environments. They might just look like a pretty concrete face on the outside, but now you know the important job they do and some of the engineering that makes it possible.
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Practical Engineering is a KZbin channel about infrastructure and the human-made world around us. It is hosted, written, and produced by Grady Hillhouse. We have new videos posted regularly, so please subscribe for updates. If you enjoyed the video, hit that ‘like’ button, give us a comment, or watch another of our videos!
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This is not engineering advice. Everything here is for informational and entertainment purposes only. Contact an engineer licensed to practice in your area if you need professional advice or services. All non-licensed clips used for fair use commentary, criticism, and educational purposes.
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This video is sponsored by HelloFresh.
Thumbnail photo and intro footage by Mike Kruce Photography. www.mkjphoto.net/
Stock video and imagery provided by Getty Images, Shutterstock, and Pond5.
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Producer/Writer/Host: Grady Hillhouse
Assistant Producer: Wesley Crump
Script Editor: Ralph Crewe

[@PracticalEngineeringChannel]

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[@danielhostetler9493]

Thanks for doing this video, it's very timely as we have a fairly large retaining wall that's just been installed behind our house in the process of building a new duplex. I'm sure it's been engineered but some other issues has been concerning and this video has addressed some of those issues.

[@Platypus_Warrior]

Why are the soil nails aligned vertically and why the vertical gap between each row remains the same?

[@pixelchi]

@@Platypus_Warrior Soil nail walls are specialty walls used only when soil types are correct and when top down construction is needed. That's right, when the wall needs to be constructed beginning at the top and going downward. The wall batter design is usually 70 degrees, the nails grouted but not stressed and installed in patterns to encourage uniform soil strengthening. The soil nail concept was invented in France.

[@lynnh7694]

Lack of drainage blew that wall out.

[@ironcito1101]

You make those meals look tasty. Alas, Hello Fresh a US-only service.

[@nfreeman7]

"I love innocuous parts of the constructed environment" is Grady's best line ever. It should be the tagline for the whole channel.

[@ianallen738]

He needs to sell the t-shirt. I would buy one.

[@siddharthiyer1120]

@@ianallen738 100% @Practical Engineering Please make this happen!

[@TestSpaceMonkey]

This belongs on the crest of a civil engineering school somewhere :)

[@SusieRascal]

I kinda like "a retaining wall in the wild".

[@tima9790]

came here for this comment would buy tshirt

[@JKTCGMV13]

Your mechanically stabilized earth video inspired many days of sandcastle building at the beach with old cereal boxes and other cardboard

[@dkaloger5720]

That’s so wholesome

[@SonsOfLorgar]

Now that's a great way to get kids interested in engineering :)

[@_Noopy_]

Genius!

[@yensteel]

Practical!

[@Lunch_box]

That was the one that made me subscribe

[@Jared-e]

I love that he’s a civil engineer and his name is Grady. Grading is very important in civil engineering. He was born for this.

[@TehVulpez]

His last name is Hillhouse, so he can also deal with the engineering of hills and houses!

[@claudias.1863]

I love this comments. 😂😂😂. Right on! 🙌🙌🙌

[@Alex.AL_26]

As a professional landscapers who has built quite a few retaining walls I can tell you that managing water behind a retaining Wall is critical for its longevity.

[@germanrodriguez7564]

99 percent of retaining walls fail due to bad drainage

[@rachelt2415]

I also learned that in Japan, retaining walls have been a focus of legislature because so many walls are too old and can't stand up to earthquakes. Tragically, a school kid died after a retaining wall failed. I live far from a fault line, so I'd love to learn more about how we build structures to stand up to earthquakes!

[@MozTS]

Maybe if the school kid was allowed to carry a gun this would never have happened

[@eragonFiniarell27]

@@MozTS Sorry what?

[@finonevado8891]

@@eragonFiniarell27 don't mind him, he's american

[@chocolatechip12]

I live in the city next to where the poor girl died. The school had been told to reinforce the wall, but apparently they couldn't be bothered, and the city looked the other way. Such a sad story.

[@HummingbirdCyborg]

@@finonevado8891, could be wrong, but I'm pretty sure that was meant to be an absurdist response not meant to be taken literally.

[@pamdemonia]

Years ago as a baby apprentice electrician, I worked on a job that went 6 stories down from the street for parking. They had built a temporary wall while excavating held up with dirt nails, but while doing that, they unearthed a shipyard (including a complete whaler!) and had to call in historians and archeologists to better preserve what they found. Because of this, the retaining wall on half the site wound up starting to fail, effecting the basement of the building across the street. All equipment was removed from the top of the hole while they figured out what to do, eventually going with longer dirt nails and restarted that half. It was cool for me as a first-year on my first big new construction job, as I learned an awful lot about how buildings are actually built. Thanks for your always interesting videos. I am always happy to see them in my feed!

[@PracticalEngineeringChannel]

Sounds like a stressful situation for the engineers and a good learning experience for everyone. Glad they figured it out before anything fell down!

[@marley7145]

@pamdemonia San Francisco?

[@freetolook3727]

How buildings are built in the classroom is not the same as buildings built in real life.

[@AK-ny5bz]

True

[@AK-ny5bz]

I true eagerly wait for his videos, as I have watched all of them already. I vividly remember listening/watching Video on Culvert while taking a walk on Konkan rural road in rainy season, while water used to cross under the road through a Culvert making kul kul sound. Ah! Nostalgic just in 3 month.

[@Biffo1262]

I only ever did the calculations for one retaining wall and I used Reynolds text book to do my calculations. As I still understand it the thickness depends on the 'angle of repose' of the material being retained (in my case sand) and the overturning moment due to the height. I was shocked to find the wall was to be 4ft thick at the base. I got my calculations checked by a Professor of Civil Engineering and he told me I was spot on. The guy I was doing the drawings for (a garage cut into an embankment with another persons house near the top of it) decided it was all rubbish and cut the ground away to build without the retaining wall. I withdrew from the job only to read about 5 months later as the ground dried out the land had slipped damaging to the the new garage and the other persons house. The idiot went ahead without local authority consent. It cost the guy big time as his insurance would not pay and his neighbours insurance also went after him. Not only that he was sued for damages uncivil court and also fined for unauthorised development. The moral is....do it right the first time.

[@tedosmundson5620]

Yes... it always better to do it right the first time. I bet the guy had to file BK before it was over unless he had assets to liquidate that the court could force him to sell.

[@harryf9885]

If his answer to someone telling him the wall had to be way sturdier than he thought was to build it without a retaining wall at all he deserved it.

[@Headhunter_212]

“I love innocuous parts of the constructed environment” is super wholesome.

[@sixstringedthing]

I recently helped a friend renovate her mother's property and they were wondering why the water bills were so high. The house has a paved terrace out front with a timber retaining wall at one end, which was starting to collapse. Turns out the mains water pipe came in under that end of the terrace, and subsidence due to the failing wall had caused the pavers to break a t-joint for a garden tap on the exterior wall of the house (poor plumbing design there), causing further washout of the soil. I'm now imagining such an event scaled up to "large civil project" size... yikes!

[@youkofoxy]

Hence the need for through terrain and soil analysis in any serious construction.

[@In.Darkness]

You miss 100% of the shots you don’t take

[@darksu6947]

@@In.Darkness Hi Darkness! 👋

[@seansecker9398]

12 years I've done civil and industrial hydrovac work. Bursting water mains are so incredible when they dig a hole for you 6 lanes in width. The ground is always moving. And seeing what happens to aging infrastructure is just incredible

[@PrivateLeffers]

Lol, the wall collapses so it's "poor plumbing design".

[@jeffc6832]

I design retaining walls (precast modular and segmental block) every day and often struggle with getting clients/contractors/architects and even other engineers to understand the basic concepts. Lots of engineers love to place cut walls right on the property line (because the architects have used up all of the space) and then they can't understand why they need easements to cut into the neighboring property in order to build the wall from the bottom-up. I think I need to just start sending them links to your videos.

[@bryceanderson4864]

😂

[@wana2oo]

my story is exactly same ... lets put inside of the wall on property line, ur structural engineer YOU have to figure it out we dont care.... architects are our archenemies (lol pun arch really fits there)

[@monad_tcp]

those damn architects

[@whirving]

Surveyor here simultaneously face palming and sympathizing. I see similar things all the time, maybe property ownership should come with a class on what it actually is and means? Good luck out there!

[@TheTobykenyon]

@@monad_tcp architects and their great ideas are the bane of my life

[@marknc9616]

I was on a housing board where several retaining walls came into question. One had experienced some crumbling near a sidewalk. We were concerned that it might collapse and injure someone. In time, we replaced I believe six retaining walls. Retaining walls were very expensive. Most builders don't build them. The only builder we could find that could build them was the same builder who built the original walls 20 some years earlier. The new retaining walls have a nice look to them. They improved the aesthetics of the neighborhood greatly.

[@alanduffell9191]

It's only a very small exaggeration to say that your videos are the reason I signed up for an Integrated Master's of Engineering with the UK's Open University. I'm just three months in but loving it. Thank you for inspiring me!

[@BillionairesArentYourFriends]

That's wonderful! Any updates for us?

[@sydneybriannataaffe1026]

I started watching your channel with the mechanically stabilized earth video as a senior in high school. Now I am about to graduate college with a degree in civil engineering. This channel has been such a big part of my path to this career. Such a fitting video for you to post

[@jannejohansson3383]

Nice, I start new rocket Business in next week and our one way trip to moon starts Jan 2022. (I watched chinese fireworks and few videos about american rockets, they sucks, I gonna make better ones and half price. All parts can compost) Have to go weld engine nozzles to backyard. bye!

[@freddoflintstono9321]

@@jannejohansson3383 OK, sarcastic as that was, it was also an entertaining send up. Point well made 😋

[@kyle5555]

@@jannejohansson3383 how is the rocket business going? Been awfully quiet. 🧐🧐🧐

[@pufthemajicdragon]

Fun fact: I was driving my sister down to visit family the other day and drove past a short retaining wall on the side of the road. I remember when it was installed about 15 years ago. When it was installed, it leaned the right way - top leaning in towards the hill. Now it leans out. Someone didn't engineer proper drainage for the wall, and Colorado's expansive soils combined with 15 years of rain have pushed the wall out. So it's interesting the timing on this video :)

[@ih82r8]

Better call the DOT and let them know.

[@shaneclarke6307]

@@ih82r8 "No problem found" will be the answer. I called about multiple safety related issues to multiple agencies with the same result.

[@ih82r8]

@@shaneclarke6307 well we can still do our part at least instead of just being cynical about it and turning a blind eye.

[@bananian]

@@shaneclarke6307 Opportunity for a lucrative lawsuit

[@railgap]

look at what happened on Hwy 36 a few years back!

[@johnclayden1670]

I've worked on heavy construction projects around the world for my entire career and still find your videos interesting.

[@YT-yami]

You're single-handedly saving my interest in my course, and quite possibly saving my future career as a barely competent Civil Engineer. Thanks 👍🏻 from a graduating student from the Philippines.

[@sophrapsune]

As someone who’s in the process of engaging an engineer to redesign a failed retaining wall at home, installed years ago by someone else, I have a new-found respect for these walls.

[@vero0992]

Do you mind if I ask how tall the wall is and what the process was to find an engineer? I'm looking to find someone to build an 8-10ft tall residential retaining wall and I know I'll need a licensed engineer, but am curious about what I'm in for.

[@Quantum-Bullet]

Vero 0 got space for 25* slope?

[@ab7011]

@@vero0992 It doesn't have to be a licensed engineer form a specific place, physics is same everywhere I am a structural engineer and I can help you with that.

[@WhatsY0UTUB3]

@@ezicarus8216 better to have a geotechnical engineer design it

[@PeterNarsavage]

@@ab7011 In the United States the engineer has to be licensed in the state the wall is located in. And because it is retaining soil, it is better to have a geotechnical engineer design it.

[@russm4677]

I've worked in construction litigation (lawyers for construction stuff) for years..... and I can tell you that failed retaining walls are about 50% of the cases I've worked with.

[@cablepratt8065]

Yikes.

[@factsoveremotions6035]

Did they have you on Retainer? 😂

[@Sleepytechnician]

@@factsoveremotions6035 I’m sure he wouldn’t crack under that pressure!

[@SamichHunter]

I remember your video on Mechanically Reinforced Earth specifically because it blew me away. The cube of earth that held up your car got me hooked on your channel and I have been enjoying it ever since. I appreciate that your channel is so informative about principles that operate in the background and go unappreciated by the general public, yet is so vital to our society in every day life. Thank you for sharing this with us. It is very much appreciated.

[@Wardc8]

As a new geologist at a geotech firm, I’m learning as I go about the engineering that follows our work. It was very satisfying to see you cover concepts I’ve worked on and to learn about others I may encounter. Thanks for the great video!

[@dougpost5111]

I live about 15 minutes from where that retaining wall collapsed in New Jersey. That entire project has been going on for more than 10 years now and it was so depressing to see my hopes of normal traffic flow literally crumble into rubble.

[@Warhawk76]

Always amazing how government projects like that one always seem to take forever. Washington state has been working on the freeway near where I live for as long as I can remember. And every time I drive by there are either people standing around, or no workers in sight. I wonder what is taking so long, until I go by and see nothing happening day after day...

[@fleshbuttbongos]

Same. That merge from 42 to 295 will forever remain shitshow.... still holding on to hope that the 55 to 42 double lanes helps with that nonsense.

[@Tokru86]

@@Warhawk76 That's usually because the private construction companies use every trick to further delay the project because this way they can milk the government for more money. Also they know that the people responsible for paying them most of the time have no clue what they are doing so they can present them with every bullshit reason imaginable for why the project takes so long of why it needs a higher budget.

[@kornykidd0]

Me too. Dysfunction junction is the worst place.

[@---do2qd]

@@Tokru86 that may be true to some extent but you are grossly underestimating the ineptitude of washington state's government

[@jdlessl]

I built a big deck on my house some years ago that involved a 4' tall poured concrete retaining wall. I was perfectly confident speccing out the posts, beams, joists, rafters, etc myself, but I absolutely sought the services of an engineer for determining how the retaining wall should go. Built everything to his exact specifications, and 4 years later the only damage I can see is some almost-invisible cracking straight down the control joints put in for that exact purpose. 5 stars, would engineer again.

[@murraystewartj]

Shelling out for that engineer's stamp is some of the cheapest insurance/peace of mind you can get. Sure does beat getting stuck with a could've should've would've moment some time down the road.

[@greenidguy9292]

@@murraystewartj I call bullshit and I’m an engineer.

[@murraystewartj]

@@greenidguy9292 Well you must be double jointed to have your head so far up your arse. I've gone through the permitting process and there's lots of engineers that may need to sign off - structural, electrical, geotechs and so forth just because it's required by law or just for peace of mind (I've always built to code or above). And the great thing about having a qualified engineer sign off on the work is that, assuming you meet their specs, should something go wrong its on them. But good for you, Skippy, in representing your profession as essentially useless.

[@StallionFernando]

@@murraystewartj lol waste of that would be, specially for a 4ft tall retaining wall. If it was a house or a giant wall then yes, an engineer needs to be contacted but for a tiny wall it's a waste of money

[@murraystewartj]

@@StallionFernando Check your local building codes. Regs vary wildly and may, for example, depend on such things as soil contitions, the specifics of the site (drainage issues for one) or other factors. I have seen gravity walls (think Allan block) of less than 4' fail catastrophically - this was in an area with high annual rainfall so drainage was the likely culprit. One I remember blew out and partially went onto the road. This was in a "rich" part of town so money wasn't an issue, I believe, just folks being cheap. If in doubt check with the local planning/permit departments, and spending a few bucks on an engineer or geotech is, as I said, pretty cheap insurance compared to the cost of a failed retaining wall, even if it's less than 4' high.

[@dwayne7356]

I live in New Jersey and I have been waiting for the report on this collapse. Immediately after the collapse, a retired civil engineer friend with connections to NJDOT told me that NJ tried blaming the contractor for not following the spec. The contractor replied with a warning letter that they submitted to NJDOT that it would fail. Then all went quiet. There are multiple ramps that were built up in this project including the half of the roadway in the picture that didn't collapse. They are still proceeding with other ramps but one has to question is what was already built wrong too?

[@Arfwid]

"slopes are waste of space".. I'm a structural engineer, within the field of civil engineering. This statement rings so true..

[@gregorylewis8472]

I’ve been a safety person for over 25 years with 15 in geotechnical construction. Your videos are such a great learning tools for our young engineers and safety people. Keep up the great work.

[@alexjohnstonjohnston5374]

I am also a 25 year veteran of Building Engineering (in the UK - but physics is physics) and I often push graduates towards this channel as additional learning beyond the help I offer. They are impeccably produced with consideration of the sequence with which you layer up understanding of engineering ideas. I lecture Architectural Students, and pacing and sequencing of learning is incredibly hard to get right - I’ve used this channel to polish up my approach to some of the more complex engineering forms. Also, having a bendy straight edge and a couple of books to act as props to explain flexors and level arms always helps!! Great content, keep up the good work PE!

[@mo938]

no wall could possibly hold all the love I have for this channel.

[@rocketman3474]

I drive by the collapsed retaining wall in NJ you featured at the beginning of the video. They put some materials on it to stabilize it but to this day they haven’t started to rebuild it. Every time I drive by i think the same thing and that it was fortunate that it failed when it did and not after the road was opened to traffic.

[@tesmike]

I live right near the NJ project. It was wild when it happened. One day it's fine and lightly raining... the next the whole side collapsed. If they ever release what happened to it I would love to see you cover their findings like you have with other project failures in the past.

[@lpphillyfan]

kzbin.info/www/bejne/fIazn3irhpajfas 42 Freeway has a lot of videos about thay project.

[@streetracer2321]

1 year later and they haven’t even started on repairing it

[@cmdr1911]

I have built all kinds of walls and embankments in Southern Ohio. I had just built a block wall with geogrid embedment and drove past a shopping center just told my wife that wall wont last. Im a field engineer so I couldn't explain it but could just see the wall was wrong. Sure enough 3 months later have a heavy rain, the block were in the parking lot.

[@aaronarmstrong9776]

It's crazy that a wall failed on a commercial job. Anyone with that big of a contract should not have a failure. It's not that complicated. I'm from Southern Ohio too

[@AnalogueKid2112]

The retaining wall along US 22 in Steubenville by the Ohio river is a sight to behold if you’re in the area. ODOT did a video here on KZbin about it recently

[@MrNicoJac]

Why did you build a block wall that you knew wasn't going to last??

[@cmdr1911]

@@MrNicoJac I didn't. I built a similar one on a gas pad that is still there 4 years later. The one that fell was one I drove past daily for a few weeks durring construction and it just seemed wrong

[@loonatticat]

@@MrNicoJac It was your job to understand that “driving past a shopping mall” meant that he was talking about a completely different wall than the one he described building in the first part of that same sentence. It would have been refreshing if a professional builder had commented “Yeah. I build all kinds of stuff around town. I do it all wrong.”

[@pixelchi]

I remember decades ago, employed by a state highway department, we in the geotechnical section tried to convince in-house structural engineers to try MSE walls, geotextiles, geogrids, soil nails, etc. but to no avail. It was cantilevered gravity walls or 3:1 slopes. If we had had Grady's simple, intuitive, learn by seeing, displays and models I think the department would have saved millions of dollars in design and construction costs by moving ahead into the future. Instead, at that time, the only way to present these concepts was by formulas, equations, graphs and (if we could get the research money) demonstration models.

[@RCAvhstape]

I'll take formulae, equations, and graphs over a youtube video, even a great one like this, to be honest.

[@sjorsangevare]

@@RCAvhstape Well the state highway department didn't.

[@m2heavyindustries378]

@@RCAvhstape Then why are you here?

[@RCAvhstape]

@@m2heavyindustries378 Just so you can ask questions

[@bananian]

And instead they go ahead and adopt SoLaR RoAdWaY.

[@sneakattack879]

This is what I love about this channel and your teaching style, I always walk away with a deeper understanding and appreciation for the civil infrastructure we all find ourselves in. Keep up the great work!

[@Monsux]

This channel ticks my autistic brain like no other. At this moment there are two new TV show seasons that I've been waiting for for months but this channel is way too addicting so I keep watching engineering videos. Thank you for making KZbin a better place. You'll get this 🥇 2021 award for the best newly discovered channel.

[@MrFayding]

Hello fellow Jerseyans, seeing our little neck of the woods is really cool. Here's to another 10 years of construction

[@Flower_Mann1803]

Nice, I might join the construction crew when I graduate.

[@bugplayer]

Each time I watch one of your videos, I'm always amazed about how little I know when it comes to engineering, how many factors you need to take in consideration when building everything and how complex it can be.

[@jannejohansson3383]

And this is just basics, something can go wrong so many ways.

[@sixstringedthing]

Fields such as aerospace, heavy marine transport and oil/gas extraction tend to have a bigger "wow factor", especially for younger people. It's only as I've grown older (and spent a fair bit of time on construction sites) that I've really started to appreciate the complexities in civil/structural engineering just as much.

[@arrikmontijo3916]

I design retaining walls on at least a weekly basis, and this video was still a delight and extremely insightful. Good job.

[@jonathankleinow2073]

I was on my HOA board for two (terrible) years, and among the many contentious maintenance projects we had to address were many retaining walls that had washed out or otherwise destabilized over time. I don't envy anyone who tries to convince stubborn skinflints that yes, it really is important to have someone who knows what they're doing to build these things, and we can't just cheapen out and do it better ourselves with stuff we buy at Home Depot.

[@1969barnabas]

In 2003, I hired a contractor to build a retaining wall for me. He told me that he had experience doing so. He decided to use railroad ties. When he started construction, I was horrified to find out that the spikes he was using to nail them together only penetrated the next railroad tie about 2 inches. I have a friend who is a geotechnical engineer. I asked him to come look at it. My friend told me everything that was wrong with the design and my friend talked to the city inspector who was assigned to the job. The inspector made the contractor do everything that my friend recommended. Needless to say, the contractor was NOT happy! The inspector made him install "dead men", which are essentially like the ties grady described that are drilled into the side of the wall. Then, he required the contractor to drill holes all the way from the top to the bottom of the wall and drive steel rebar all the way through.

[@wk8219]

Even before the video started my thought was, “OMG, this looks so fascinating. How the heck does this guy make stuff that I would’ve thought was boring so darn interesting?“ Thanks for another great video.

[@freddoflintstono9321]

In my experience, even boring things start to get interesting when you start looking into them. It may not be *your* interest, but it's always fascinating to talk to people who do something in depth for a living. This is also how you recognise a REAL expert: they can explain what they do without the need for any jargon (unless explained).. You never stop learning, and the best way to check if you know something is to explain or teach it to someone else..

[@WillDMcQ]

Im a practicing archaeologist who spends a lot of time on construction sites when they are doing subsurface work and your videos are both entertaining and professionally valuable! A wise operator once told me that it only takes 1 yard of dirt to kill you. Retaining walls may be invisible but they are so critical!

[@DonCherrysDream]

Yup! 1 cubic yard of sand weighs close to 3000 pounds. As much as a car!. If you're in a trench and the surrounding soil collapses, you will be crushed to death almost instantly. That is why on construction sites where soil is being moved or dug out, you see alot of shoring and walls. All in the name of keeping the surrounding soils from caving in and causing massive damage to equipment and/people

[@Harry_Paratesties]

Cubic yard

[@SoulDelSol]

What do you mean by retaining walls are invisible?

[@jorgegonzalez-larramendi5491]

@@SoulDelSol mmm when people don't notice don't even think about it..

[@SoulDelSol]

@@jorgegonzalez-larramendi5491 oh interesting, I always take note of retaining walls and look at them. Seriously I find them interesting and cool looking. Not even kidding. Kinda sad other people go through life so blind (now kinda kidding but still partly serious)

[@petermitchell5240]

Thanks for making this video! I love the demos you provide, they make understanding the physics so intuitive

[@kevsha6797]

YES!!! I watched this disaster happen and have been living through the traffic of the constant construction and the aftermath of the collapse for a decade now. As soon as it happened my first thought was "Man, I really hope Grady covers this"

[@mallardbeacon6502]

Thanks to videos like these I massively overdesigned my own retaining wall in my garden and now it will last a few centuries at least

[@Notimp0rtant523]

I love how in the intro you can see just the tiniest hint of a glimmer in the eye, a slightest twist of the smile as Grady thinks to himself “I’ve been waiting to sneakily lobby for retaining walls for so long”

[@jackprier7727]

His joyfulness at sharing his cool explanations makes him one of the great you-tubers-

[@Dr-wheel-barrow-opperator]

What a great learning experience I just had from all of your clear explanations as well as your perfectly built demonstration display. A genuine thank you from me.

[@capnthepeafarmer]

Your simple demonstrations are so valuable to explain these concepts, even as a seasoned engineer just helping to visualize something is so valuable. Visualization is so important as an engineer especially when trying to explain a concept or a problem to someone not technically literate.

[@adventureclub8332]

great day when Practical Engineering upload

[@cesarsantis5116]

I love the fact that you use models and not CG to explain the things!

[@0ptixs]

This is exactly the video I wanted to watch! The city is building a new overpass near where I live, one side has huge sloped earth up to the road, and the other side has a huge (10-15ft tall) retaining wall and every time I drive by there I always think how can they keep that soil from spilling out! Thank you for this

[@juggernaut7_]

Practical Engineering sponsorships are one of the few sponsorships I watch and/or take seriously.

[@NameNaameNameeNaamee]

Is there an official award for well made and valuable content on the internet? If so, you should get it! What you are doing is just invaluable, especially for younger folks. Channels like yours make the internet better, and given the fact that the internet - for better or worse - is a part of everyones lifes today, we owe you our gratitude. Thank you very much!

[@--Paws--]

In aquascaping almost every hardscape/decoration is a retaining wall. It will either loosely hold substrate to mimic a natural scene or secure that the substrate doesn't erode over time to keep the aesthetic.

[@petertimowreef9085]

You know you're watching a fantastic educator when they make you feel smart. That thingamajigger you built with the dowels is so easy to understand.

[@james2042]

My mom has a retaining wall behind her house, she got it put in because she wanted her yard to be flat in 2 levels. That 4 foot rule applied exactly here and thats how tall the wall was because "they cant make a wall over 4 feet without city involvement" fun fact the wall has collapsed 3 times

[@stevelopez372]

Wow. That’s rough, since the City involvement is not necessary for retainers four foot or less the contractor is free to build off the top of his head, thus constant collapse and replacement. Perhaps the city has standard engineered walls in a hand out for the public to use. In SoCal the building depts have such handouts for the public. For short retaining walls. More expensive but less problems in the long haul. Good luck.

[@james2042]

@@stevelopez372 If I ever get one built on my property I am definitely making them build it at least 4.5 feet so they have to build it right

[@toastedt140]

@@stevelopez372 Lmao imagine thinking the way they do things in Cali ougbt to be THE standard. Stay on that dope bud

[@eekus1494]

@@toastedt140 Imagine thinking making plans for an engineered retaining wall available to the public is a bad thing.

[@greengoodman1]

That’s probably a factor of not digging the wall down deep enough (at least 1 course buried) and then digging the trench of drainage rock underneath (another 6 to preferably 9 inches) plus backfilling the wall with drainage rock and weed barrier. You can do small walls right or you can do them cheap, but not both. We have a 2ft wall around our 24x12’ pool and it’s abysmal. It isn’t trenched and there’s no drain rock. The water had nowhere to go but to push all the tiny bricks out, and mason glue isn’t going to help fight that! I have to replace it, it’s such a mess.

[@SamuelKristopher]

Hey Grady! Could you pretty please do a video one day on how engineers construct the parts of a bridge that go down into the water and rest on the riverbed, and support the bridge structure - I don't know what they're called really (the legs?). But they are like magic to me - I don't understand how they built them, or how they don't get swept away by the currents of the river. As I read somewhere, they often use these sheet piles that you mentioned in this video to create a water-free space right down to the riverbed where they can start putting the foundations? Would totally love to see a video about this! Love your channel!

[@SamuelKristopher]

To be specific, I live in St Petersburg (Russia) and these bridges were built in the 1870s, and I just can't imagine how they did it back then.

[@ikeaaron]

I strongly second this request!

[@massimookissed1023]

Grady's vid on building underwater kzbin.info/www/bejne/i4OmYmVrrNWAiZY You can build a temporary dam down to the river bed, then pump all the water out, leaving you a clear river bed to work on.

[@jaredpatterson1701]

Yes, I agree. It's hard to find videos that show them sucking water out and installing metal plates, and I am curious how they pour concrete for underwater too! And what exactly sits on the concrete I beams! I've seen plates, metal, but I never see them pour concrete on for the actual road

[@PracticalEngineeringChannel]

I have a video that covers some aspects of bridge pier/bents that someone linked below.

[@paulhaynes8045]

Although I'm not an engineer (of any sort) this video did strike home on a personal note. A couple of years ago I built a patio in our back garden, and because it was on a slope, I ended up having to build a six brick high retaining wall at one end. I've never done anything like this before, so I just laid some concrete footings and built the wall! (Back filling with soil.) I did include a few drainage holes to stop water building up, and laid the wall double, with more substantial footings (the rest of the patio base was single brick) - and of course the ends of the wall are 'tied' into the two side walls. But I did all this by gut instinct - without any real understanding of what I was doing. After all, it was only a patio! Now I'm sitting here wondering how silly I might be looking in a few years time...

[@jackprier7727]

We've all done that, I think--my lesson from Grady is to put the footing on the upper side so the dirt hold it down for ya- cool!-

[@ChrisWunsch]

Yet another brilliant video Brady and team!! Thanks! Proud to be a sponsor of such great content!

[@dotmanmide]

I'm building a retaining wall at the moment for a new overhead road bridge. This is helpful.

[@olekaarvaag9405]

0:27 "I love the innocuous parts of the constructive environment. " And I love anyone who would say something as geeky as "I love the innocuous parts of the constructive environment. " ❤

[@horizonbrave1533]

Man, it just makes me realize that even just the things that faciltate construction and building are far beyond my life of mental knowledge! I like how there's so much engineering in retaining walls..and the wall itself sometimes isn't even the project! And great end of video cooking bit, I love these!

[@erff-eu7kg]

The soil-shear failure mode is really impressive, I had never heard of that. Are there any notable examples of such a failure?

[@bc-guy852]

As a former Caterpillar equipment salesman I've never stopped looking at 'innocuous parts of infrastructure'. And it's why I subscribed to your channel after the first episode I saw! (Way back when you were building acrylic flow demonstrators in your garage!)

[@alanargent5422]

"I love innocuous parts of the constructed environment". It is that love that makes this channel so good.

[@aldenconsolver3428]

Always glad to see a new Practical Engineering show up :). On this one, I am a geologist (and planetary scientist) and it is an axiom in geology that no retaining wall will last forever, usually not even for human lifetimes. If a geologist was asked to build a retaining wall we would come up with something with footings, columns, drains and plants with good solid rooting systems and still know bye and bye the earth will win.

[@grundewa]

It's really a shame more retaining walls don't make use of the ever-faithful flying buttress :)

[@suburban404]

Fellow Geologist. It all eventually erodes away and settles on the ocean bed.

[@aldenconsolver3428]

@@suburban404 right O, if your land is getting higher you probably have more problems anyway.

[@caty863]

It's not planetary science, it's "earth science". Don't be ridiculous by trying to sound general. Your "planetary science" doesn't apply to Jupiter now, does it??

[@aldenconsolver3428]

@@caty863 Yes it does, I was educated at Caltech and have taught planetary. Take geology and throw in atmospheric dynamics (yeech) and more physics. Less fun, I made it through but didn't enjoy it at all, nor was I able to get any kind of non-academic job.

[@Zodliness]

It's difficult to appreciate the effort and technologies involved in heavy construction without informative videos like this. It's not contemplated in the average persons daily life.

[@danielstuber8972]

i live in PA and i saw this collapsed wall in person while driving through NJ! i immediately thought of this channel and was going to request you cover it, but I see you are already on it! great video :)

[@Jthomsonhate7]

"I love innocuous parts of the constructed environment." May be the nerdiest thing I've ever heard and I love it!

[@soldtobediers]

Though from 1986 to 2009 I'd only had 23 years experience as an inspector of new construction over highway & bridges for Txdot... Grady has, & continues to ~ cover every building aspect of it; with an understandability to the traveling public, second to none. -William 'Rock' Gilpin District 2.

[@Mircea020]

Thanks to you i'm seeing everyday structures differently than most people do. An honor to be one of your subscribers. 🙌

[@weignerg]

This was just what I was hoping you would do a video on. Thank you!

[@HowardR911]

I've been wondering for a long time why residential basement walls don't collapse under the pressure from the surrounding earth. This video answered some of those questions but I would enjoy a video or other discussion of how these ideas apply specifically to residential basements. As always, thanks for the good work!!

[@Andrew.Drennan]

Typically these arent very tall and the house structure acts as internal bracing to an extent.

[@craigjensen6853]

They certainly can. Especially older CMU basements.

[@djsomeguy]

Basements typically have footings too, not just the vertical foundation walls. They're also a square box so they have something to resist the sideways forces, so long as the walls themselves don't bend and fail.

[@TheRealE.B.]

It helps that basement walls are not vertical cantilevers. They can be thought of more as beams spanning from the basement floor to the basement ceiling (which is why horizontal cracks running across the middle of the wall are scary... that's the wall splitting open under pressure). It also helps that they have the weight of the house pressing down on them and holding them together (think of how you can hold a stack of books sideways by pressing them together so they don't fall down).

[@mazevx2451]

So over here, the basement is known as the most expensive part of the house and that's for a reason, every single house and especially the foundation and basement must be engineered to strict criteria depending on soil type, location slope and the rest of the house. The planning engineer is held accountable for the construction and has to present to control the build process, reinforcement layout etc. And that's only for a single family home. Public buildings like schools and such have even stricter rules.

[@uriel1417]

You should have mentioned the failure modes of retaining walls more clearly, overturning, bearing failure, sliding failure and how we design to stop them.

[@kori228]

Yeah, sounds more like this would be a Part 1 introducing the topic

[@firstnamelastname7476]

agree.. I'd love many hours on this topic. But I think Grady keeps things short and simple for general/(younger?) viewers.. Perhaps he'll do a part two or revisit the topic once the investigation on that collapse is complete.

[@muddleddjinn]

I had no need for any of the information, yet I am hooked . Thank you for your videos and channel ✌️

[@petercarioscia9189]

I live very close to this collapsed retaining wall in NJ. It's amazing to see such a construction failure up close and first hand.

[@jackielinde7568]

Grady, I don't know if you've been following the spec house building project on the KZbin channel the Essential Craftsman, but they're building a house on the side of a hill, and early on they had to create two sets of retaining walls for the project. It's a pretty neat set of videos. I think you'll like them. They're now finishing the mechanicals inside the house as far as video timeline is concern. But the house is completed and already sold. (Shucks, Grady. You missed out on your chance to move to the Pacific Northwest by about a month or two.)

[@PracticalEngineeringChannel]

I have watched every single video since the beginning of the project ;)

[@TasosKtd]

I started watching your channel because of interest on a specific topic. I kept on watching this channel because of the quality of your work. Keep up the interesting, well-presented videos!

[@superzman06]

One of the best vids on retaining walls!

[@idrivea911]

Your little practical demos are fantastic. The concepts you show with some dowel and acrylic summarize a lot of my college classes in seconds.

[@Raptorman0909]

One of the most deadly things on construction sites are trenches, they may in fact be the cause of more fatalities than any other thing. Trenches are voids with walls on either side. The weight of soil is not to be trifled with.

[@matthew8505]

This video is SO good that we use it as an introduction to our new engineers at our wall design company

[@user-hr3mi2sp7c]

Great video as always. I've been practicing Civil Engineering for almost ten years and am always impressed at how well you're able to break down and illustrate concepts that felt so complicated when I originally learned them. Jist curious have you ever thought about getting into teaching?

[@freetolook3727]

One thing that I learned in ninth grade science class was a thing called "hill creep". It's a natural phenomenon whereby any manmade object (telephone pole, road, wall, etc) placed on a hillside is subject to the natural forces of gravity and hydrology. That's why you see telephone poles on a hillside angled precariously, even though when installed, they were level.

[@trueriver1950]

There is a famous tower in the city of Pisa, Italy that demonstrates this effect in a rather awesome way that does wonders for the tourists trade

[@MGSLurmey]

@@trueriver1950 The leaning tower of Pisa is that way because of settlement, not hill creep. Slightly different phenomena.

[@sashajohnson9041]

I'm finishing up a foundation design course this week. We covered shallow and deep foundations, mats, retaining walls, and a whole host of geotech topics. It was an invaluable class for me to take, and seeing this video come out today on my last week of class was the cherry on top. Thank you Grady!

[@davewilson9772]

Always a treat to watch your videos Grady. Thanks!

[@Snaily]

This video explained an insane number of engineering things where I live that I've always wondered about about but never known how to Google/ask about.

[@alecbonerchamp7399]

I love learning new information from you while I work!! Thank you for doing what you do Grady!

[@aSinisterKiid]

This is so cool to see you discussing something in my area. I live in Burlington County and drive by this area quite often. I had no idea this failure even occurred so it's fascinating to hear about it now.

[@Weaverkins]

Your knowledge of and excitement about these topics always draw me in. Thank you for teaching me and so many others about things we wouldn't think of otherwise.

[@jaxrammus9165]

that mechanically stabilized soils video was the first video i saw of yours, been watching since and loving the content. good job.

[@proscriptus]

Fun fact, residential brick house walls often have weep holes, and homeowners who don't know what they are often seal them up, with predictably unfortunate consequences.

[@googiegress7459]

There's gonna be weeping, either way

[@PWN_Nation]

"There are only 3 types of retaining walls: 1) Those that failed 2) Those in process of failing 3) Those that WILL fail" - Mike Hadduck

[@Roy-vn8wh]

Was going to make the same comment

[@MAGdumpKY]

Randomly Ended up on this channel and I love it. every video keeps me glued..

[@stevemurphy6599]

Civil engineering is a fascinating science. Thank you for bringing it to us in such an understandable way

[@kholdanstaalstorm6881]

It's good to learn a little each day, thank you Grady for providing me with some learning today! Marvelous episode, looking forwards to the next one!

[@edj2022]

I have to drive past that highway project in New Jersey 2 times a day; on the way to and from work. The collapse is a disappointing setback because the project is supposed to fix a major bottle neck area of major roads on the NJ side of the Delaware river just outside of Philadelphia. Thanks for the video!

[@truthandreality8465]

Hosted, written, and produced by civil engineer Grady Hillhouse, Practical Engineering is the world’s largest, most subscribed-to, most respected and best video channel for civil engineering, architectural engineering and construction with no compromises or restraints. Once again you have given us the video that becomes the curriculum. BRAVA, endless BRAVA!!

[@rmehta54]

Yet another excellent video about engineering. Thanks. A few days back, I noticed some abstract patterns on the sidewall of an underground station. I knew it was made by seeping water and admired them as abstract art. But now I realize and appreciate they were made by water seeping holes in the concrete wall holding the tunnel up. Art produced by Engineering!!

[@aharnishanand8501]

As a civil engineering student, this just makes my course more and more interesting... Thanks...!!

[@cjespers]

Grady does it again! Love your videos. All the best!

[@XX-kf7mx]

You have have really put an efforts to make this video to explain it to us in easy and simple terms. Big fat thanks to you.

[@theradarblip1070]

Hey Grady! Thanks for the educational video. I am working in an old 50+ years hydropower plant, which was built in the mountain gorge long the path of alpine river. There are many constructional tunnels, caves, stumpings and other ground works that still stand after so many years, it would be great to know how these structures are kept from being collapsed, and in some ceilings and inwardly concaved walls I saw these tips of the rods or rebars that stick out. Could you please make a video on how the tunnels are kept from collapsing under enormous mass of the mountains that they are bored through. Thanks and keep up the great content coming!