Xinhuanet publish significant progress in the construction of Gaoligongshan Tunnel. 34.5 kilometer long longest tunnel in China.  Tunnel start at Nujiang Station and arrive at  Longling Station on the Dali–Ruili railway in Yunnan province. Tunnel in earthquake zone under Himalaya geology Indian Ocean plate collide Eurasian plate. Extreme risk and difficult tunnelling.

Major milestone achieved on June 23. Longest inclined tunnel shaft 3850 metre No:1 of Gaoligongshan Tunnel reached main hole. A dag earlyer 640 metre deep shaft No:2 finished. Now main tunnel construction can start. It is major milestone.

Gaoligongshan Tunnel use "through horizontal guide + 1 inclined shaft + 2 vertical shafts" method. Very dificult geology. The protection deformation cracked up to 19 times, and the shotcrete cracked seriously. It use double-layer arch frame, initial support reinforcement and another second lining.China Railway Tunnel Bureau improved tunnel cooling and concrete high temperature environment research.

Xinhuanet publish "The maximum in-situ stress of No. 1 inclined shaft is 31.22MPa (megapascal) horizontal stress, and the strength-stress ratio of surrounding rock is 0.06, which is equivalent to 3122 tons of weight per square meter of construction work surface, which belongs to extremely high in-situ stress. The ambient temperature of the inclined shaft construction is above 38℃, which exceeds the threshold value of orange high temperature warning for tunnel construction in China"

Tunnel bored by tunnel boring machine Colorful Cloud No.1"( 彩云一号). It start on 28 August 2017 will finish  31 May 2022.

http://big5.xinhuanet.com/gate/big5/www.yn.xinhuanet.com/newscenter/2020-06/26/c_139168012.htm