Extension of Sakuradori subway line in Nagoya — construction PDFs

[Tenorikuma]

I thought I'd link two PDFs showing how the extension to one of our subway lines was constructed. They used a round boring machine to create the tunnels, followed by a train and equipment that placed the concrete lining pieces and rails as it went.

 

What I'm curious about is why the east and west-bound tunnels are sometimes built at different elevations.

 

http://www.kotsu.city.nagoya.jp/dbps_data/_material_/localhost/_res/about/_res/pdf/02heimen_100521.pdf

 

http://www.kotsu.city.nagoya.jp/dbps_data/_material_/localhost/_res/about/_res/pdf/04koujihouhou.pdf

[KenS]

What I'm curious about is why the east and west-bound tunnels are sometimes built at different elevations.

 

One reason would be if they didn't have the width between something else (other tunnels, building supports) to put them side by side, and had to overlap them slightly.  If stations are close to the surface, they may be restricted to running within the boundary of a street above to avoid building basements and sub-basements.

 

Large buildings, like skyscrapers, are often built on a web of pilings that goes down hundreds of feet in softer soils, sometimes all the way to bedrock, so you can't just tunnel under them.

[Tenorikuma]

The tunnel seems to run quite deep at the point where the elevations diverge. One tunnel cuts straight through a hill, while the other follows the contour of the hill. Looking at a map, there was a water treatment facility in the general area, so maybe there are some deep water mains or reservoirs in the area.