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内昆铁路青龙背隧道于20000423贯通。青龙背隧道位于四川省宜宾县境内,全长4104ｍ,是内昆铁路北大门的第一长隧道。内昆铁路北大门隧道贯通
Nei Kun Railway Qinglongbei Tunnel 20000423 through. Qinglongbei Tunnel is located in Yibin County, Sichuan Province, with a total length of 4104m and is the first long tunnel on the north gate of Neijiang Railway. North Kunming Railway North Gate Tunnel through