The 53.85km Seikan tunnel in Japan is the longest and
deepest rail tunnel in the world. It passes through
Tsugaru Strait connecting the Hokkaido and Honshu
islands.It was built 100m below the seabed and includes
a 23.3km submarine portion. It was officially opened in
March 1988 and is used for the operation of express trains.The tunnel
was sponsored by Japan Railway Construction, Transport and Technology
Agency and is operated by JR Hokkaido. The internal height and width of
the tunnel is 7.85m and 9.7m respectively.The tunnel was built using
168,000t of steel, 1.74 million cubic metres of concrete and 2,860t of
explosives. Seikan Construction Bureau was the main construction
contractor. Two stations, Tappi Kaitei and Yoshioka Kaitei, are located
inside the tunnel.