Here's the situation: a thin concrete wall needs to go up, but it's a very large diameter, say 1 km. The wall thickness is on the order of 20 cm. The wall only needs to be maybe 3 meters high.
I'm assuming a giant single mold shaped like a ring is not practical. Instead, there are multiple molds, shaped as pieces of arc, that the wet cement is poured into.
The thing is, how do you make the wall uniform? I'm thinking the concrete will shrink as it cures, so there will be a gap between each poured piece of wall arc.
Is there some way around this? How do you incrementally extend the wall without gaps? I'm trying to imagine some separater, like a plank of wood, blocking one end of the mold. Once the next mold is set up and poured, you can pull out the plank. But is that practical? How do you seal the plank against the mold so there are no leaks? Besides that, how would you press the sides of the mold together hard enough so there aren't any leaks there either?
I forgot to mention this is non-reinforced concrete.
The environment is kinda cold. I'd say yearly ranges would see -25 to +25 Celsius. However, I would very much love to hear about thermal expansion and how to handle that.
IDK anything about ground conditions. I'm just imagining normal dirt. Someone mentioned a possible need of footers but I can't see that. Remember this wall is very thin. 20 cm thick and 3 meters high. That sounds pretty light to me, but if necessary, I would consider a flaring base for a snowshoe effect. Drilling to the bedrock for footers seems pretty expensive, so some kind of built-in foundation via a flaring base would be my first thought.