The section from Ya 'an to Linzhi in sichuan-tibet railway is called the most challenging railway project, one of the reasons is the dangerous terrain. Located in the southeast of Qinghai-Tibet Plateau, the surrounding mountains are high and deep, and there are few people. There are many mountains and rivers, such as Nyainqentanglha Mountain, Dadu River, Jinsha River and Yarlung Zangbo River. At the same time, the activity of the land plate is frequent, which is prone to all kinds of natural disasters. In addition, about 86% of the lines are tunnels, 10% are bridges, and there is almost no normal subgrade, which is a great test for construction, design and operation. A little carelessness may affect the development and progress of the whole project.

According to media reports, the amount of construction work from Ya 'an to Linzhi in sichuan-tibet railway is particularly large. First, nine super-long and ultra-deep tunnels should be opened, of which Zheduo Mountain Tunnel is 32,766 meters long, with a maximum buried depth of 1.630 meters, Haizishan Tunnel is 25,080 meters long, with a maximum buried depth of 1.220 meters and a length of 29,370 meters. Milla Mountain Tunnel, Zilashan Tunnel, Yelashan Tunnel, Boshulaling Tunnel, Duomuge Tunnel, Gong Yi Tunnel and Sejilashan Tunnel have a maximum buried depth of1.872m, which not only requires multiple inclined shafts, but also has a long construction period, which is quite challenging and difficult for workers.

At the same time, sichuan-tibet railway crosses five geomorphic units and seven rivers, such as Jinsha River, Lancang River, Nujiang River and Yarlung Zangbo River. Climb over 8 high mountains such as Erlang Mountain, Zheduo Mountain and Gaoersi Mountain. The overall terrain is high in the north and low in the south, high in the west and low in the east, and the landform conditions are very complicated. In addition, sichuan-tibet railway passes through the abrupt terrain belt in the eastern part of Qinghai-Tibet Plateau, where plate collision and tectonic activity are strong and earthquakes are active. These complicated geological and geomorphological conditions make the planning and construction of railway engineering face great challenges.

Frequent mountain disasters are one of the main challenges facing sichuan-tibet railway's construction. From Chengdu in the east to Lhasa in the west, sichuan-tibet railway jumped from the second step at an altitude of 500 meters to the first step at an altitude of more than 4,000 meters. The Chengdu-Ya 'an section of the railway has been opened, and the Lhasa-Linzhi section has also started construction. At present, the proposed section from Ya 'an to Linzhi is the most difficult section in sichuan-tibet railway, with the bridge-tunnel ratio exceeding 90%.

The border between Ya 'an and Linzhi in sichuan-tibet railway is the transition zone between the first step and the second step. The altitude suddenly rose from 500 meters to 4000 meters, and the terrain was diverse and complicated, which had a great impact on the construction. Repairing the railway has extremely high technical requirements and great construction difficulties.

There are many mountains and rivers, high mountains and deep valleys, and the terrain is extremely complicated. It is best to build a railway on the flat ground. Once you encounter the terrain of mountains, rivers or plateaus, it is a great test for construction, design and operation. Railway construction is recognized as the most difficult construction.

If such a difficult line can be completed, it will not only greatly shorten the running time of the Chengdu-Lhasa railway from 36 hours to 12 hours, strengthen the connection between them and promote the economic and cultural exchanges of surrounding cities, but also change the backward traffic conditions in mountainous areas and build a land passage to South Asia.