Abstract: The Shergyla Mountain tunnel is one of the controlling projects of the SichuanTibet railway with a length that is larger than those of the mountain railway tunnels built or under construction in China. It faces a steep plateau terrain, complex geological conditions, a harsh plateau alpine environment, and strict environmental protection requirements. Consequently, tunnel construction will face unprecedented technical problems. A series of studies, including those on the complex mountain crossing lines in the plateau area, separated and incorporated construction of tunnels, overall construction methods of extralong tunnels, and disaster prevention and rescue, have been conducted based on tunnel environment and engineering, hydrogeological conditions, and the key and difficult points of construction. In this study, targeted designs on the tunnel boring machine (TBM) section, TBM equipment selection and key technical requirements, long and large auxiliary tunnel, and crossmountain disaster prevention and rescue are analyzed and discussed, and a complete set of design schemes is put forward for hard rock burst prevention and control under high geostress. Taking the Shergyla Mountain tunnel as an example, a 38 kmlong mountaincrossing tunnel, a separated tunnel construction scheme with open TBM as the main scheme and the drillandblast method as the assistant scheme, two rescue station settings according to the design concept of "humanoriented, orderly evacuation, safe waiting for refuge, and limited time rescue," and a comprehensive rockburst prevention and control technology of "early warning, active and passive prevention and control, and safety protection of operators" are recommended. The relevant designs can provide references for the design of long and large mountaincrossing tunnels in a complex environment for similar projects in China in the future.

Key words: Sichuan-Tibet railway, Shergyla Mountain tunnel, tunnel boring machine, extra-long tunnel, disaster prevention and rescue, rockburst prevention and control