It returns obviously. Making repair or replacement of damaged sections economical is one of the engineering challenges. This by itself suggests compartmentalizing along the same lines I suggested.
It would probably be ideal if you could factory make each section and ship it on a standard truck, but with the growth of additive manufacturing, other possibilities also open up, like 3D printing the large metal container onsite.
I think you'd have to print it onsite, otherwise you have no gain in the loop being underground as you'd have to dig basically the entire ground up to swap sections.
