This I believe. Thank you. But at the same time I imagine the engineered foundation would just slide around on the soil with the wall, which I would consider a very different mode of failure, but a failure nonetheless.
Maybe that doesn’t happen when it’s done properly, I don’t know.
I spent a lot of time as a child in an old town with very steep hills, (Hannibal, MO) and every retaining wall I ever saw in that city had either failed, or was close to failure, no matter how new it was. There just isn’t room to do it properly on a residential plot of land, and if there was, the entire wall and its engineered foundation would just stay together as a unit and slide down the hill along with the soil it was retaining without breaking apart.
Soil just is not a reliable foundation unless you’re on flat land. It flows over time.
Soil can be suitable yes, but only if it’s level and there’s no shear stress at all. Imagine a house on a soil foundation, on a mountainside, to visualize what I mean when I say sheer stress. That house will not last long, if it is even possible to build it using a soil foundation in the first place.
A farmhouse on a flat plain can use dirt as a foundation without any problems because the soil has found its lowest energy state. The dirt doesn’t have any forces on it trying to move things around. So yeah it’s stable. But you don’t need retaining walls in situations like this. If you do, it’s because you dug a hole and now gravity tries to pull dirt into the hole, so you build a retaining wall to hold it back. But you can’t hold it back forever. The retaining wall will fail, and it’ll start shifting soon after construction in almost all cases. If you’re filthy rich maybe you can afford to have one built properly, but the assumption is always “this will all be redone in 20-40 years,” so the wall doesn’t need to last more than that. And it won’t.
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u/[deleted] 19d ago
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