Retaining Walls: 2d. Retaining Walls Reinforcing Cantilever And Basement Walls With Toys

Very good. Let's take a look at this toy or model for a cantilever retaining wall that is attached to its foundation. It's sticking up here. There's nothing up top, and there's dirt on this side, and the dirt is doing the active lateral soil pressure and pushing on that wall. Now, if there's not enough friction with the ground, then the wall will slide. But as long as there is some friction, and let's say it rained, and this starts pushing a little bit more against that stem of the retaining wall, then what happens here is the stem, this face will go into tension, this face will go into compression. So we're going to need a lot more rebar on the tension side. compared to the compression side, the concrete can handle most of it. On this side, it might be a larger rebar. It might be tighter spacing than on this side, but there is a definite difference between the two. Now, what happens on the heel, this backside of the retaining wall? What happens here is, let's say, there's all this dirt. What happened to the focus here? Focus quick. Very good. So there's all this dirt on the backside of the retaining wall and it's pushing down on that heel. So what happens here is the heel is subjected to the weight of all that dirt and so it starts doing that and its top goes into tension, into stretching, and its bottom goes into compression. And we're going to need a lot more rebar on the top or a different spacing compared to the bottom that is in compression. So if the wall doesn't slide and it doesn't sink into the ground, the remaining worry is overturning. So as this active lateral soil pressure starts to push against the wall, if there is resistance down here because the soil has traction, Then what happens is there is a resultant of the triangular load at one-third, two-thirds, and then there is this resistance, and these two are fighting each other, and they're probably equal, otherwise it would have slid. So if they're equal and fighting each other, what they end up doing is rotate the wall. So these two are going to do that. So what happens to the toe in that case? As you push against me, the toe is going to end up doing that. and therefore its bottom is in tension and its top is in compression. And that's what's happening to the toe. So just recapping, under this active lateral soil pressure, the stem is doing that, which is essentially the dirt side is in tension, the opposite side is in compression. Due to the weight of the soil, the counterweight on the backside of the retaining wall is pushing down, all that weight is making the heel do this, top in tension, bottom in compression. And because of the lateral push of this dirt on that retaining wall and the resistance due to the soil, there is an overturning. And that overturning is resisted by this soil and it ends up doing that. Bottom intention, top and compression. Heel, top intention, bottom and compression. Stem, dirt side, intention, opposite side, and compression. Very good. Продолжение следует... Продолжение следует... Продолжение следует... Продолжение следует... Продолжение следует... Продолжение следует... Продолжение следует... Продолжение следует... Продолжение следует... Продолжение следует... Продолжение следует... Продолжение следует... Продолжение следует... Продолжение следует... Продолжение следует... Продолжение следует... Продолжение следует... Продолжение следует... Продолжение следует... Продолжение следует... Продолжение следует... I wanted to compare what we just saw, which is essentially a cantilever retaining wall to a basement wall. Here's a basement wall. It's attached to the slab on grade down here and attached to the top, to the first floor slab or floor up here. versus the cantilever retaining wall, it's free to move. So looking at the basement wall, as an active lateral soil pressure pushes on that-- come on, focus, good-- pushes on that basement wall, what happens here is this is the dirt side, the dirt is pushing, and therefore this is assumed to be a pin connection, let's say a precast wall, then this face is in compression, the opposite side, the tension, sorry, the basement side, the inside is in tension versus the outside, the dirt side is in compression. Now if this were a cast in place concrete wall, which makes this a rigid connection and another rigid connection and subjected to this active lateral soil pressure in the basement pushing on that wall, what happens here is pretty much the same, compression tension, but it's acting from here to here because that pin and that pin are now rigid and they will not allow rotation. So it's a little bit less slender than the previous example, but still this is a compression face. This one here is a tension face. I hope this helps. Продолжение следует... Продолжение следует... Продолжение следует... Продолжение следует... Продолжение следует...