Working Out the Construction Details

I had the concept but have no idea how the structure could be constructed in real life. I researched underground tunnels and subway systems (a little different as there was a gap between the tunnel and my structure). 

Googling random words about "supporting pipes" finally got me to look at industrial pipes and then to "pipe saddles" used in water service and power stations that were also load bearing (made to stop unwanted movement, give insulation/dampening to prevent abrasive wear). Previously, I had deduced that a tunnel of that size wouldn't be able to carry it's own weight as well as the weight of people with just a clamp, so it needed some sort of base. "Pipe saddles" gave me a lot of ideas as to how my tunnel could be supported and even had dimensions for a tunnel that size/weight.

Just some pictures that started off my drawing process of working out details of construction:

I-clip used in-situ to support heavy pipe.

Pipe Saddle With Multiple Gussets.

Strong concrete base.

Possible way of securing the tunnel to wall.

The origin of my clamp idea. (I-clip on saddle)

Another way of holding pipe in place.

"Designed to provide support between the steel pipe and its supporting structure."
Used for electrical isolation and abrasion control of mains and by industry for load distribution, energy conservation, and electrical insulation protection.

 

 

 

Extended edges to prevent rolling.