Longest Tunnel


Well-known member
Labeled as world's longest automobile and rail tunnel. At 18,000 meters, The Fehmarnbelt tunnel will link the Danish island of Lolland with the German island of Fehmarn. It is said the tunnel will cut travel times between Scandinavia and Central Europe to under ten minutes, while contributing to tourism and both countries' green transitions.

The Femernbælt Link tunnel at 17.6km (10.9 miles), when completed, will certainly take the record as the world's longest combined rail and road tunnel.

Other notable "longest tunnels" are:-
Although I am often amused why city underground metro lines, in "tunnels" but not through mountains, are usually excluded from such discussions.
Although I am often amused why city underground metro lines, in "tunnels" but not through mountains, are usually excluded from such discussions.
Quite. London Underground's Northern Line tunnel between East Finchley and Morden is 27.8km (17.3 miles).
Just think, the Hoosac Tunnel located in Western Massachusetts between Zoar and North Adams was once the longest tunnel in North America at almost 1 mile, when it opened up for business in 1875. This tunnel held the record until the tunnels were built through the Rockies in the early 20th century.

This tunnel has many firsts that have become commonplace with tunnel construction. This is the first tunnel where boring machines were used to dig the tunnel. The first boring machine tried in 1852 failed due to getting stuck in the very hard stone on the East Portal side. The boring machine had successfully cut the "little" tunnel in North Adams prior to being moved overland to the East Portal side but couldn't handle the East Portal. This was due to the machine not having any power and the fact that the mountain on that side has some of the hardest rocks on record being comprised of compressed quartzite and compressed granite.

This construction made use of blast patterns used to dig the tunnel. This came a long much later in the construction after Doctor George Mowbray was brought in to assist with blasting the tunnel in the early 1870s. Being an explosives expert, he worked out the blasting pattern used to accurately blast the stone using a controlled charge.

It was George Mowbray's discovery of trinitro-glycerin and the later development of dynamite that helped speed up the construction. The discovery of trinitro-glycerin happened accidentally during a cold winter morning as he was rushing jars of nitro-glycerin along a slippery road. His cart overturned and he didn't blow up!

The tunnel also utilized shafts placed along the route that reflected light from conning towers placed at key points along the ridge.

Today, boring machines, really not much different than the early ones except ours are more powerful and a lot larger, the controlled blasting using patterns are still used, and a SAT-Nav replace the light towers to guide the tunnel construction.

What's interesting is how close the Navies were when they met inside the opened tunnel. They were off maybe 4 inches over the length.