On April 7, 2020, the key control project in Sichuan-Tibet Railway (Lhasa-Nyingchi Section) under construction - Milin tunnel was successfully holed through, and the Zangga tunnel was holed through on the same day, marking the completion of all 47 (216.5km) tunnels in the Sichuan-Tibet Railway (Lhasa-Nyingchi section). It is an important milestone in the construction of the Lhasa-Nyingchi section and lays a solid foundation for the opening to traffic of this section on schedule. It is also an important achievement of the railway sector in implementing the CPC Central Committee and the State Council's deployments of "stable employment, a stable financial sector, stable foreign trade, stable foreign investment, stable domestic investment, and stable expectations" and accelerating the construction of key projects.
Located in Milin County, Nyingchi City, Tibet Autonomous Region, Milin tunnel is one of the six 10,000m long tunnels with the greatest difficulty in the entire railway. With an average elevation of 3,100m, a total length of 11,560m and a maximum burial depth of about 1,200m, Milin tunnel is described by railway builders as the "toughest challenge" and the most dangerous obstacle. The successful holing-through of the tunnel has provided new experiences in railway tunnel construction under extremely harsh natural conditions, which will provide a very useful reference for the Ya'an-Nyingchi section of Sichuan-Tibet Railway under planning, in terms of technical R&D capability and engineering construction practice.
Sichuan-Tibet Railway (Lhasa-Nyingchi section) is the first electrified railway in Tibet Autonomous Region. With a total length of 435 km and a design speed of 160 km/h, it is located in the southeast of Qinghai-Tibet Plateau, one of the regions with the strongest crustal movement in China. The railway stretches along the Yarlung Zangbo River suture zone between the Gangdese plate and the Himalayan plate on the Qinghai-Tibet Plateau, and over 90% of the railway is located in the plateau more than 3,000m above sea level. With 16 crossings over the Yarlung Zangbo River, it runs in steep mountains and deep valleys, where the complex environment has brought great difficulties to construction.
Since the commencement in December 2014, 20,000 railway builders have bravely fought day and night to overcome difficulties such as high altitude hypoxia, awful climate and harsh environment. They have strengthened the project quality and safety management, optimized construction organization, and strengthened scientific and technological innovation to promote the project construction with high quality and high efficiency. Especially since the outbreak of the COVID-19 epidemic, the railway construction units have coordinated on the epidemic prevention and control and the railway construction, strictly implemented various prevention and control measures, worked hard to reduce the impact of the epidemic, ensured the health of construction workers and realized the project progress on schedule. Up to now, all 47 tunnels, 119 bridges (120 in total) and 115.11km track of the section have been completed. It is expected that track-laying of the whole section will be completed by the end of 2020 and it will be put into operation in 2021. The opening of Sichuan-Tibet Railway (Lhasa-Nyingchi section) will end the history of no railway in southeast Tibet. It is of great significance to pushing forward the poverty alleviation along the railway, boosting the development of tourism and mineral resources, and promoting the economic and social development of Tibet.
In the construction of Sichuan-Tibet Railway (Lhasa-Nyingchi section), the railway builders, aiming at the special geological conditions of the plateau, have strengthened their efforts to tackle key scientific and technological issues and to explore innovative technological methods. They have solved the world-class tunnel construction difficulties such as aeolian sand, toxic and harmful gases, high ground stress, high ground temperature, moraine bed, etc., developed and applied a series of construction technologies such as windbreak and sand fixation, comprehensive temperature reduction, prevention and control of water and mud gushing, and comprehensive control of rock burst, accumulated many mature construction technologies and management experiences and registered 32 patents (including 13 utility models and 19 inventions), which will play an important role in the construction of Ya'an-Nyingchi section, whose natural environment, geological conditions and construction difficulties are very similar to those of Lhasa-Nyingchi section in Sichuan-Tibet Railway.