A Fuxing bullet train runs on the Lhasa-Nyingchi railway in the Tibet autonomous region on June 24,2021.Jiao Hongtao/For China Daily

Construction on the third section of a high-profile railway connecting Sichuan province and the Tibet autonomous region is ongoing,a political adviser told Xinhua News Agency recently.

"The Sichuan-Tibet Railway is a strategic project with many challenges,including a complicated geological structure,which will make construct extremely difficult,and a sensitive environment in the region,"said Lu Chunfang,an academician of the Chinese Academy of Engineering.

Lu is also a member of the Chinese People's Political Consultative Conference National Committee and general director of the Qinghai-Tibet Railway,the first railway in Tibet.

Lu and his team has carried out research on the Sichuan-Tibet railway,proposing more than 100 technical suggestions,the Science and Technology Daily reported.

Upon completion,the Sichuan-Tibet Railway will cross eight mountains,and more than 93 percent of the line will consist of bridges and tunnels,Lu said.

The line will include six tunnels stretching more than 30 kilometers,with the longest tunnel 42 km,he said,adding that the tunnels will not only be long,but also buried deep underground.

"The deeper the tunnel goes underground,the more pressure it puts on the rocks,"he explained,which will create a higher risk of collapse.

Building the bridges will also be problematic.

"The bridge that will pass over the Nujiang River will be 610 meters tall,which is nearly the same height of Shanghai Tower,China's tallest building(632 m tall),"he added.

Tibet's sensitive environment is another issue.The line passes 75 environmentally sensitive points,including natural reserves and water conservation areas,all posing challenges to construction,Lu added.

The 1,838-km Sichuan-Tibet Railway project is divided into three parts.

Two parts have been completed and are currently running.The Chengdu-Ya'an section in Sichuan opened in 2018,and the Lhasa-Nyingchi line began operating last year.

The third and most challenging section,linking Sichuan and Tibet between Ya'an and Nyingchi,began in 2020.

The date of the railway's planned completion has yet to be revealed.

Upon completion,the railway will be the second to link Tibet with the rest of the country,following the Qinghai-Tibet Railway,which opened in 2006.