1 铁路上的长大隧道是指其两端洞口的洞门墙间的距离超过5000m的隧道。到1991年底为止,我国铁路上共建成了15座这类隧道,总长度约为100km,占当年全国铁路隧道总长度的4.5％。 2 这些隧道分别位于京广(2座)、大秦(2座)、成昆(2座)、襄渝(2座)、京原(2座),京通(1座)、焦柳(1座)、南疆(1座)、溪田(1座)等9条铁路干线和盘西(1座)支线上。分布在我国的华北(北京、河北、山西)、东北(辽宁)、西北(新疆、陕 1 A long tunnel on a railway refers to a tunnel with a distance of more than 5000m between the door openings at both ends of the tunnel. By the end of 1991, a total of 15 such tunnels have been built on our country’s railways, with a total length of about 100 km, accounting for 4.5% of the total national railway tunnel length in that year. 2 These tunnels are located in Jingguang (2 blocks), Daqin (2 blocks), Chengkun (2 blocks), Xiang Yu (2 blocks), Jingyuan (2 blocks), Jingtong (1 block) Block 1), Xi Tian (Block 1) and other 9 railway lines and Pansi (Block 1). Distribution in China’s North China (Beijing, Hebei, Shanxi), Northeast (Liaoning), Northwest (Xinjiang, Shaanxi