Project introduction: the tunnel is on West Sichuan Plateau at an elevation of 3,400m and goes through Mt. Zhegushan 4,500m above the sea level. The main tunnel is 4,430m long, with following features: 

Low temperature: extreme temperature is as low as -31.1℃. The mountain top is covered with snow all the year round and the winter lasts 8 months. 

Low pressure: pressure at the tunnel exit is 68Kpa, 60% of the same at the sea level; 

Low oxygen: oxygen in the air is 13.7%, 67% of the same at the sea level. 

The tunnel is at a high elevation: tunnel bottom 3,400m above the sea level, and mountain top 4,500m above the sea level; 

High technical intervention: construction in plateau, less oxygen for personnel and equipment; complicated geological conditions, large deformation and such other technical problems need a solution.

In metamorphic rock area, the tunnel encounters complicated geological structures and too much underground water. Experts have repeated field investigation and argumentation. Zhegushan Tunnel for the current is the most complicated one in Sichuan Province for geological conditions.

Since its application in 2004, after the 5.12 Great Earthquake, Zhegushan Tunnel has achieved significantly in eliminating freeze injury and still works well today.