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This makes sense and, although I didn't include it in my comment, the buoyancy was part of my curiosity. While it's clever to take advantage of the buoyancy cre

This makes sense and, although I didn't include it in my comment, the buoyancy was part of my curiosity. While it's clever to take advantage of the buoyancy created by the air cavity, if they're nearly-buoyant that would also mean that the variability in traffic would create a significantly variable (as a percentage) load. I wonder how this is accounted for. For the record, I don't think I'm "gotcha-ing" the engineers by thinking of these questions. I'm sure there have been answer to these questions since before the project began, it's just that I would like to know the answers. They also must have a way to seal off segments in case of a water breach? Although, that seems awful given there will be human traffic in the tunnel

mattashii 5y ago
See the video for answers: After putting in a segment, the trench is backfilled with rocky material (over the segment), so that any buoyancy is negated by the fact that it's held down by a large layer of rocks. This layer presumably also prevents most, if not all, leaks from generating instant floods in the tunnel. Lastly, once completed the project will result in 5 parallel, but mostly independent tunnels (two train tunnels, two highway tunnels, and a service tunnel between the highway tunnels). I presume that the tunnels can be isolated and waterproofed seperately.