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I expected there to be some kind of "foundations"? i.e. once the water is out of the enclosure, you have a surface that is likely to be soft wet mud or sand. S
by SideburnsOfDoom 6y ago
I expected there to be some kind of "foundations"?
i.e. once the water is out of the enclosure, you have a surface that is likely to be soft wet mud or sand. Surely you want to scoop some out, dig down and lay some big blocks of stone under the river bed level?
Or maybe that happens, but was just not shown. Or maybe, once you start building up, the sheer weight pushes the whole column down until it settles.
- evgen 6y agoDig to bedrock or drive in pilings to shore up your foundation if you can, it all depends on the local geography. Given the lateral forces on a bridge it seems unlikely that modern builders would float the footings of the arches in the riverbed, but in the case of this bridge I think that was what happened (a guess given the fact that three arches failed during a flood in 1890s when a pile-up of logs and debris forced a lot of water flow to push deeper to pass the bridge.)
- prennert 6y agoIn the book the issue was that the sand around, and eventually under, the foundations washed out over time so the piers started to be effectively suspended from the bridge rather than supporting it. Rubble around the actual foundations were needed to defuse the drag of the water around the foundations, preventing the washout.