Gotthard Base Tunnel
The Swiss have solved one of Europe's great problems: The Alps make shipping freight expensive. A decade ago, miners began digging outward from two 2,600-foot vertical shafts in Sedrun, Switzerland. They've since moved 31 million tons of rock to connect Italy to Germany via high-speed rail through the world's longest train tunnel, 35.4 miles long. Manufacturer Herrenknecht built four 3,000-ton boring machines for the project, and after one of them encountered a zone of dangerous soft rock, crews began using a unique system of deformable steel rings to hold the tunnel open. The Gotthard will double freight capacity through one of Europe's most vital trade corridors and will cut an hour from the four-hour trip between Zurich and Milan.
I guess if you can't get two from the outside to meet in the middle, you then have to start in the middle and work outward. Seems odd to me but what do I know.
I saw a documentary on this. A wacky amount of dirt is being moved. I'd have used some sort of electric train that has a push pull or regenerative braking. It would help negate the energy losses. I think this is one of or the most expensive civil project going.