【Domestic News】The Longest Railway Inclined Shaft of China Completed Successfully, Construction of Gaoligongshan Tunnel Accelerated
At 8:08 am on June 23, with the sound of a blasting, the longest railway's tunnel inclined shaft in China, the main shaft of No. 1 inclined shaft of Gaoligongshan Tunnel reached the tunnel successfully. The main shaft of No. 2 vertical shaft, which has a depth of 640.2 meters, has also dug to the end on the previous day afternoon. The achievement of two major node goals in succession marks that the drilling and blasting section of the Gaoligongshan Tunnel has officially entered the construction phase of the main tunnel, increasing the excavation work surface from 10 to 16, accelerating the construction of the project.
With a total length of 34.5 kilometer, Gaoligongshan Tunnel is a key control project for entire Dali-Ruili Railway, also the longest railway tunnel in China. It is located in the Himalaya earthquake zone, squeezed by the collision of the Indian Ocean plate and the Eurasian plate. having the geological features of "Three Highs and Four Actives", of which the geological complexity is rare even in the whole China. It includes all the geology difficulties and risks that a tunnel construction may has. The difficulty of its construction is second to none in the history of tunnel construction in the world.
The whole tunnel adopts the auxiliary tunnel setting scheme of "holing-through pilot tunnel + 1 inclined shaft + 2 vertical shafts". The main shaft of No. 1 inclined shaft, which was excavated to the main hole today, having a length of 3850 meters long, is the longest inclined shaft in the history of Chinese railway construction. Its geological condition is very complicated, resulting in the initial support deformation cracking for 19 times, with serious shotcrete cracking and serious block loss.
Liu Yafei, General Engineer of the Inclined Shaft Area of Dali-Ruili Railway Project of CRTG, said that after testing, the maximum crustal stress of No. 1 inclined shaft was horizontal stress, which was 31.22 MPa (megapascals), and the strength-stress ratio of the surrounding rock was 0.06, equivalent to each square meter of construction working surface bears the weight of 3122 tons, which is classified as extreme crustal stress. At the same time, the ambient temperature of the inclined shaft construction is above 38℃, which exceeds the orange high temperature warning threshold for tunnel construction in China. For this reason, all parties involved took measures such as optimizing construction schemes, adjusting support parameters, improving process methods, and shortening the closing time, taking double-layer arch trusses, implementing primary support and secondary lining, and increasing the frequency of monitoring and measurement, forming a whole set of large deformation control technical measures to overcome the extremely high ground stress challenge.
In order to mitigate the negative effects of high ground temperature during construction, CRTG also actively explored and applied tunnel cooling technology and carried out research on concrete materials under high temperature environment to effectively ensure normal construction.
While the No. 1 inclined shaft has its difficulties, the construction of the No. 2 vertical shaft also faces numerous tests such as water gushing and collapse. The maximum water inflow of No. 2 shaft reaches 141.8 m3/hour, far exceeding the safe water inflow of 10 m3/hour during the construction of the shaft. Standing within waterfalls and torrents, wearing raincoats and rain boots, workers construct waterfalls and pedal torrents in a small environment, which is extremely difficult.
"The shaft 2 of Gaoligongshan Tunnel this time is 14.4 kilometers away from the exit of Gaoligongshan Tunnel. It can create two more working surfaces and play an important role in the long tunnel." Lu Yanqun, Deputy Manager of the Inclined Shaft Area of Dali-Ruili Railway Project of CRTG introduced that, the No. 2 shaft had a depth of 640.2 meters, which was 40.2 meters more than the Canton Tower in Guangzhou, which has a total height of 600 meters.
The Gaoligongshan Tunnel, under which CRTG undertakes the construction task of 29.3 kilometers, has the most selection routes (24 routes), the longest design and construction period (10 years), the longest main tunnel (34.5 kilometers), and the longest inclined shaft (3850 Meters), the deepest vertical shaft (762.6 meters) and eight other No.1 records in China.
"The Gaoligongshan Tunnel is China's first super project to cross the Hengduan Mountains. Its construction will help to better understand the geological conditions of the Hengduan Mountains, accumulate tunnel construction experience under extremely complex geological conditions, and provide experience for equivalent projects such as Sichuan-Tibet Railway. Realistic case." said Liu Jianbing, deputy director of the Engineering Department of the Yunnan-Guizhou Railway of Shanghai-Kunming Passenger Line.
The Dali-Ruili Railway starts from Dali in the east, crosses the Lancang River and Nu River to the west, crosses the Gaoligong Mountain in the western part of the Hengduan Mountains, and finally reaches Ruili. The total length is about 330 kilometers, and the passenger train target speed is 140 km/hour. The Dali-Ruili Railway is an important part of the Trans-Asian Railway West Line that integrates and serves the China’s "Belt and Road" initiative. It is of great significance to achieve cross-border cooperation with neighboring countries, strengthen interconnection and interconnection, and accelerate the development of border areas in ethnic areas.
After the Dali-Ruili Railway is completed and opened to traffic, the travel time from Kunming to Ruili will be reduced from 9 hours on the current road to about 4.5 hours, ending the non-railway history of Dehong Autonomous Prefecture in Yunnan Province.
Li Maoying, Yang Hu, Ji Lin from People's Daily
Photo / Huang Zaiyun