Abstract: To clarify the characteristics of single and doubletube extralong mountain railway tunnels, a statistical analysis is conducted on 310 extralong mountain railway tunnels. The lengths of doubletube extralong mountain railway tunnels built and under construction in China and those in Asian and European countries are summarized. Statistical results show the following. (1) For the extralong mountain railway tunnels in China with a length of 10~15 km, the ratio of the single to doubletube tunnels built is 18∶1, and the singletube mode is the most popular in the tunnels under construction. (2) For the extralong mountain railway tunnels in China with a length of 15~20 km, the ratio of the single to doubletube tunnels built is approximately 1∶1 and that for the tunnels under construction is 20∶1. (3) For the extralong mountain railway tunnels in China with lengths above 20 km, the doubletube singletrack is commonly used in tunnels built, and the ratio of the single to doubletube tunnels under construction is 5∶2. (4) By the end of 2020, considering the total number of the extralong mountain railway tunnels built and under construction, singletube tunnels have increased by approximately 30%, whereas doubletube tunnels have increased by approximately 1%. (5) The mountain railway tunnels in Asian countries (except China) with lengths above 20 km are singletube doubletrack tunnels, whereas those in European countries are doubletube singletrack tunnels.

Key words: extralong railway tunnels, mountain tunnel, single tube, double tube, tunnel length, distribution characteristics