3 ms·
He’s talking about soldier pile and lagging walls in this part. See https://www.coastaldrillingeast.com/capabilities/shoring/soldier-pile-lagging-wall/ https://
by abduhl 5y ago
He’s talking about soldier pile and lagging walls in this part. See https://www.coastaldrillingeast.com/capabilities/shoring/soldier-pile-lagging-wall/ https://www.coastaldrillingeast.com/capabilities/shoring/sol... for pictures. There are other types too (sheet pile, drilled pile, etc.).
Using these as “permanent” support is usually not done for corrosion reasons as you point out. They can be made into long term support elements but it’s costly and only done when footprint is essentially like in the middle of a city in between buildings. The buildings basement walls are designed for the entire lateral load as if the support of excavation system is fully corroded and gone, so most basements are very over engineered against earth load type failures.
Long term is generally 30 to 100 years in civil engineering, depending on when the structure was built. So beyond that life yes it’s a tear down on paper to rehab below grade.
- CoastalCoder 5y agoThanks, that's really informative. So what's the trick with something like the Hoover Dam, where (I'm assuming) major reworking every 100 years isn't acceptable? Did they find some way to avoid steel, or maybe make it piece-wise replaceable?
- lmm 5y agoI think they did it all with non-reinforced concrete, which can last more or less forever. It has good compressive strength but hardly any tensile strength, so they'll have had to design the dam in a way that doesn't depend on that.
- jacobolus 5y agoYes, 2.5 million cubic meters of unreinforced concrete. According to Wikipedia they took some core samples in 1995 and found the concrete to be stronger than when it was poured. "Last more or less forever" sounds about right. There is some steel involved, in embedded cooling pipes that were used to speed the concrete curing process and later filled with grout.
- abduhl 5y agoLarge concrete dams like Hoover are almost invariably arch dams which are shaped so that the entire dam goes into compression as the water load comes on, so there is no real need for tensile steel. These dams can take decades to cure and just get stronger over time. The connections to the rock are usually reinforced - steel that's encased in concrete is generally thought to be relatively immune to most corrosion effects for the design life of any particular structure (plus a lot longer if it's maintained).