WHY Retaining Walls FALL down - How Most people Build them Wrong

All right, guys. We got a pretty full show today because we're going to talk about why retaining walls fail. And it's because of this stuff right here. Seems like a lot of people don't understand that. So, today we're going to go out to a few different sites, look at some walls that look perfectly fine, but once you watch this video, you're going to understand that looks can be deceiving. And we're also actually going to demonstrate exactly what this stuff does and how to use it and why it's so vitally important to the longevity of almost every retaining wall that's ever been built out there. So, what are we waiting for? Let's get into today's video. [Music] All right. So, how does Geog Grid actually work? Well, let's actually do a demonstration using two boxes. Now, these boxes are going to represent back fill retaining walls. The box itself is the retaining wall or structure. And we're going to see what happens when we don't use geog grid. We're going to put sand in and we are going to compact it. We'll pack these boxes up. [Music] And we're going to do both boxes the same, except this box is going to have geog grid placed in it as we go up. The reason I'm doing this video is recently I had a customer tell me that he watches all of my videos and he built a retaining wall and then the retaining wall fell down which didn't give me very much confidence in my ability to explain the importance of geog grid in a retaining wall. It was a homeowner that built a 14t tall wall. You can see I got the grid in there and then had a catastrophic failure. If your retaining wall is over 4t tall or has a slope behind it or a sir charge, that means the weight of a building kind of like this house behind me, your retaining wall will need geogrid. No ifs, ands, or buts about it. It's what holds them together. Retaining walls fail a lot like a balloon rupturing. They'll give you the early signs that there's a problem. And as soon as you start to get that inkling that something could be going wrong, it's already wrong, you guys. So, the reason I'm using sand is because it's one of the most difficult materials to actually work with. Although it's a good material, it has no cohesive nature. So when you're actually back filling with sand, it's actually fairly susceptible to movement because it's not binding itself. So, in this case, we're going to be relying 100% on the geog grid to do all of the support of these uh columns that we're building. Now, I'm adding water to the sand just to help it stick a little bit more. [Music] I'm basically going to build these up till I run out of sand. I can put in another layer of grit. [Music] So, I'm putting the same amount of lips in, same height on both of them. Let's put our last piece of grit in and we'll finish off these. Now, there's a number of different ways we can actually test this grid. One of the ways is by shaking the table, and you'll see which one holds up better. The other way is by doing something a little bit more actually applicable, which is the static load test. Because when you build a retaining wall, you've got to take into consideration, is the retaining wall just holding up a hill or is the retaining wall holding up a structure or like a house, a parking lot or something along those lines. That's considered a static load. Boom. We have some weights right here which are going to help represent that load. Now, let's see how they do. All right, let's just build up and see how it goes. Guys, I've never done this test before. Putting the same weights. These are 2 and 12 pounders. Now, we got some five pounders. we got a five pounder. It looks like this one's done. Let's take our another five pounder from the done side and put it over here. Let's go with two and a half. Let's go another 2 and 1/2. This is a 25 pounder. That's going to probably bust it. Okay. All right. Let's go. So this will be this is another 25 pounder. Okay. So the weight slid off. Even with the weight sliding off, we were still able to maintain more of the shape on this side than we did with this side. So let's let's keep going. See if we can't get that weight centered onto it. 25. That one's done. Let's just call that what it is, guys. That one's done. That one. Importance of grid. This will demonstrate that we lose some around the edges. But this is where the retaining wall, your actual wall is only containing the edges of the soil. So, ideally, when we put in the right amount of grid and we do it the right way, the soil itself holds itself together and all you've got to do at that point is contain these edges which tend to slough off. And this wall is failing, too. So, as you look down it, you can see the base is shifted. I mean, and look at these tears. This is where a lot of guys go wrong is right on the corner of a terrace because it's very difficult to get compaction. So, you've got to take extra time. Right here, this is where And see it there. Yeah. And you can see it there. You see how they've separated? See that? Because right in this area right here, Frankie, behind this wall, they can't get the they can't get the compactor to do as good of a job or they're just Well, they you can, but it's a lot more difficult. And so, you'll see it's there and over there. You see the same thing on the other other side, right? There's a number of problems with this wall. And then on the other end of it, it's already leaning over. This whole corner is in a state of failure. So, it's all coming forward. They use good block. They used uh this looks like keystone. Yeah, that's a keystone block. It's got fiberglass pins for reinforcement. That's a good block, but bad building techniques. Yeah, you can see where the whole wall is just shifting and and in a state of failure. I don't even see any of that matting in here. There's no geog grid in this wall at all. I mean, you're not supposed to be able to see it, but when you can see it on one row, typically that becomes the installation technique of the contractor to do it multiple times. They they usually don't make a mistake because that just means they're sloppy. So, they they either show the grid or they don't show the grid. And so they've got in this entire wall one row of grid. So this wall is going to fall into this house and it's not going to take very long. Oh my gosh. Okay. So we do have another row of grid. Look at it. It goes Oh yeah. Yeah. The grid is actually settled down. Okay. You need a putty knife, Frankie? Okay. So, we're going to do a quick drive by on this development that I built. So, you can see even with the walls, the boulder walls, I'm using pretty massive stones on those things to keep them secure so they don't slide. Do you use that black matting in them, too? Depends. On the stone, depends. Depends on what the soil is like behind it. It's not a 100% for sure because if it's a heavy wet clay soil behind the the the boulders that that will this the silt from the clay will fill up the the fabric and then it'll it'll plug it up and create hydrostatic pressure behind the actual boulders themselves. Yeah. And can create problems. So, okay you guys, Frankie asked a really good question and I think I provided a somewhat confusing answer and so I want to make sure that we're pretty clear on what I'm actually talking about. A boulder retaining wall gets built exactly the same way as a modular block retaining wall in regards to geogrid. Geogrid always gets laid behind the retaining wall every 2 feet. And that rule of thumb is that you put one linear foot behind the wall for every linear foot of face wall. So that means if you have a 6ft tall retaining wall, whether it's boulder or modular block, your geog grid has to extend 6 ft behind it. And that geog grid has to be put in every 2 feet without fail. Not 3 feet, not 4 feet, every 2 feet or it's ineffectual. I hope that's a real word. But with a boulder retaining wall, you have one more step that you will never do on a modular block retaining wall, and that's to add a heavy filter fabric behind the face of the wall as you're building up. And the only reason that you would put filter fabric behind the face of the boulder retaining wall is to compensate for the gaps. You see, boulders don't tend to fit together snug. And so you'll need some kind of material in there that will help keep the soil from eroding through the face. But you've got to be careful because there's times when you want that fabric and there's going to be times when you don't want the fabric. The times you don't want the fabric is when you have a heavy soil that has a lot of silt because that soil can then plug up the fabric and lead to blowout. And that's exactly why you never use that fabric on a modular block retaining wall because the blocks fit together tight enough that they'll hold the soil back. They don't need any additional help. So that fabric can then become a liability. I hope that makes sense. You know, there's times like if it's a a sand or something like that or a sandy gravel or more of a porous material for sure cuz you want to keep the erosion from occurring between the boulders. But on a heavier clay type of soil, it can actually be detrimental. Can it has a reverse effect. So on boulder retaining walls, you know, all all walls depend upon uh building the the earth behind the wall for its real structural uh support, but um all walls have different requirements that you got to meet. All right, you guys. Now, in another video, what we're going to do is take what we've learned about geog grid and retaining wall construction and start to test it on realworld sites. We're going to look at a couple retaining walls that once you start to understand the basics of geog grid and um geoengineering, they don't make sense. And I want to walk you through these retaining walls and show you what I mean so that you can hopefully start to take what we're learning today and actually see it in action in realworld jobs. So make sure you stick around for that video. Let me know in the comments down below what you thought of this. Did this demonstration of how geogrid work actually helped you guys understand it at all better? The reason I did this is because, like I said, I went out to a customer's site, 14 foot retaining wall, and he didn't have any geogrid in it. And unfortunately, his wall fell down in 2 years. And that's when I realized I'm not covering this topic well enough. And so I want to beat this over your heads that it's the most important thing for any retaining wall over four feet tall or if the retaining wall has a slope behind it or a sir charge the weight of a building. It becomes found fundamentally the most important thing you can do. God bless. Go get them and check out these two videos right here you guys. And make sure you stick around because we are going out to site and looking at a couple walls that just make you kind of go hm. See you on the next one.