Retaining walls and Geogrid- How a retaining wall fails pt2

how are you guys today we're covering geogrid what it is and why it is fundamentally the most important element in any retaining wall construction once the wall reaches four feet has a sore has a slope behind it or has a surcharge or the load from a building behind it now if you're just tuning in make sure you go back to the first video because in that video we actually do a hands-on demonstration showing how effective geogrid is at retaining soil and holding it together in comparison to a retaining wall built without it so check that one out and today what we're doing is we're taking the lessons that we learned in the first video and actually going out on to real job sites and analyzing retaining walls using the knowledge we gained in the other video to look at these walls and to make yourself ask a question are these walls built the right way and once you start to understand the fundamental principles of geogrid you start to see things behind the scenes that otherwise would just look perfectly fine so we're going out to some sites today and checking out some retaining walls that just make you go hmm all right so now we're gonna go into two sites return arguably almost virtually impossible to build but yet you're gonna find retaining walls there how tall do you think that wall is 16 to 20 feet right so from what I've taught you so far how long how far back do you think the grid lengths need to be to make that wall right 20 feet so it's a one-to-one ratio for every foot of wall height you should have one foot of geogrid behind it you can kind of you can start to cheat on shorter walls by using a bigger block right but once you get over a certain height which is typically 11 feet you can't cheat anymore cheating doesn't work you've got to go back to the old engineering principles which means you've got to get the right amount of grid in I mean what would and when we look at this wall Frankie do you see anything that would prevent from getting the right amount of grid in like a garage that obviously was never moved the telephone pole was potentially moved because if I look at it I can see that it's a different color than the one next to it but thank courage I don't think was so to get this group this wall in place 18 foot back means that they sacrificed on the geogrid structural these guys I mean aesthetically these guys did a decent job on this retaining wall but structurally you've got a question if everything is in place to make it right and the grid on a wall this high is more important than the block the block actually just becomes a second secondary in the entire structure of the thing in fact when you do this right you can literally take the block off and all the soil will stay in place just from the geogrid as long as you've got it in installed properly so the block itself becomes almost like a facade at that point and what about this wall I'll tall is this wall Frankie five feet and is there a surcharge on this wall yep so you look at this law right here I mean this this is kind of a dead giveaway I mean we've got 18 inches of clearance on a 5 foot tall wall there's no way that this wall has geogrid in it and it's got a surcharge from this building unless the footings of this building go down deep enough that it's not presenting a surcharge and then they wouldn't have needed a retaining wall in the first place they could have just put a stone facade up so it looks to me just from what I can can gather that here's another potential problem area and for sure right here this is a for sure there's no question about it so the building could have footings that go deep enough that it doesn't impact a surcharge on to this retaining wall but the sidewalk does not the asphalt does not you see this car above the wall the wall will you stand by the wall for me for a minute Frankie we've got a 5 foot tall wall 4 foot 5 foot somewhere with a surcharge on it this wall should have two possibly three layers of grid each layer of grid needs to be 4 to 5 feet back and they did not put that in because you could tell the parking lots not been altered or changed so there's too many indicators on this wall saying that corners were cut although the wall looks good it's not built the right way here's where guys got at contractors can screw themselves pretty bad whether they give a warranty or not matter if there's faulty craftsmanship or faulty work they're on the hook no matter what happens to that wall if it's built the wrong way now if they built it the right way they're off the bus if it fails but if it built the wrong way which here it is because you could otherwise see where this parking lot would have had to been cut right where that car sitting they would have had to cut that remove that portion of the parking lot and that was then never happen so these guys like to use hybrid systems I was here when the company was installing this wall I actually called up my engineering company because I could not believe what I was seeing and they were using this hybrid system where they take a wall like this and you can see that the sidewalk was never replaced in fact like it there's there's where the sidewalk was replaced here's the old sidewalk so the sidewalk wasn't replaced and I know it wasn't because I was here when they were building it and literally all they were doing was putting this porous aggregate behind it and I've seen other youtubers do this it doesn't work and theory it works in practicality it doesn't work because as we look at this wall we can actually see this wall is already failing this wall is not that old this wall is already sliding down because of just the slight surcharge from the sidewalk it's not a big one but it doesn't have to be a big one and even in these small zones because you can't get grid in here so this is a building owner paid for this wall and they're going to be repaying for it to have it built because once a wall goes into a state of failure like you see on this one they pop like a balloon these first indicators the little signs the separation the leaning the tilt those are the signs like blowing up a balloon blah blah blah and then that balloon Pop's catastrophic failure they rupture and you can actually see on this wall as you look down it the top is actually starting to cantilever over they couldn't get the grid in they didn't have permission to cross the property line so as we look at this they were limited to that fence line it's gonna be a ditch hard to see you guys but this is actually leaning in you can see where the sidewalk has shifted and adjusted right here and that's as the wall moves out the sidewalk and everything follows suit well let's go up around the corner and see if we can spot how this looks as we transition around here I don't know it might not be as bad as it looks from the bottom and a lot of those weeds help cover it up you can see it look down you can see it's going that way because they built this 12 to 14 foot tall wall but we're limited by this fence this fence has never been removed you can look at the fence you can see the rust you can see where this fence was never touched that fence would have had to been taken out to build this wall the right way wall comes down the fence comes out they excavate all the way back into here heck you're gonna be back here with your oversizing to get 12 to 14 foot grid links at the very bottom and no core Phil nothing you can't cheat them they cut it catches up to you you can't cheat on retaining walls this is a wall I built about five years before that one yep so to build this wall meant I had to actually have a hoist come in and hold up I actually called the crane in Frankie we see these electrical poles I actually held them in place so that I could dig as close as I possibly could to them so that I could do it now what you see behind there's a couple of things that are wrong even with my wall you see those trees behind there when they start when I seen they started planting those trees behind my wall I actually came out here and I said you can't do that and they're like it's our wall it's our site we can these trees are going to make my wall fail eventually because they're gonna keep growing up the root balls are gonna grow down that's a dynamic load and that means that that trees going to if it catches the wind it's going to be doing this sort of thing and my walls my wife that was a building could hold it up I mean because it's designed to hold up an actual alleyway so that fence is a separation of an alleyway I could hold up I could hold up that building right there but I can't hold up something that is not it's not designed to hold it up to keep it from moving and that's what those trees are going to do that's the difference so you can see where these trees are putting pressure on it so this this wall is actually designed to hold up this entire alleyway some questions about Jubran and why it's so important now some of you guys are going to be asking me well what do you do in a situation like you just pointed off those two last retaining walls how do you build them well you either build them right or you don't build them at all you can't cheat on a retaining wall and if you do cheat it unfortunately will eventually catch up to you so sometimes it's better to just walk away from a job than to try to tackle a job using unproven structured methods sometimes it just better not to do the retaining wall there's going to be times when you're going to get calls to do a project and if you know that you can't do it the right way that doesn't mean you should do it the wrong way because the next guy is willing to do it the wrong way never never cave on quality never not even what is though is that the right way I want to say it never came never never something quality it's a word something on quality all right if you guys know the word I'm looking for put it in the comments down below because I can't figure it out just whatever you do build them right your reputation depends on it that's all I got for you today guys god bless and go get off her out what that word is what is the word I'm looking for