On May 11, the Desheng Tunnel, a control project of the Sichuan-Qingdao Railway, was successfully completed after nearly ten years of construction, laying a solid foundation for the opening of the Chenghuang section of the Sichuan-Qingdao Railway within the year.
Desheng Tunnel is located in Songpan County, Aba Tibetan and Qiang Autonomous Prefecture, Sichuan Province, designed by the Second Institute of China Railway, constructed by the Second Bureau of China Railway and the 16th Bureau of China Railway, with a total length of 22,943 meters, which is the longest single-hole double-track railway tunnel built in China, which officially started construction on September 1, 2014 and broke through on May 11, 2024.
The body of Desheng tunnel has crossed the three fault zones of Longmen Mountain, West Qinling and Minjiang River, the bad geology is extremely serious, the surrounding rock is mainly phyllite, slate, sandstone interbedded, soft and hard alternately, among which the phyllite is softened by water, and the stability of the surrounding rock is very poor, so the industry insiders call the Desheng tunnel "drilling holes in the pulverized coal pile".
The tunnel has the characteristics of "four poles, three highs, and five complexities", the proportion of large deformation of the whole tunnel is as high as 32.6%, and the problems of tunnel face collapse, mud gushing, water inrush, and large deformation occur more than 300 times, and the construction safety risk is extremely high, making it one of the most difficult cross-ridge tunnels in the mainland.
"After the opening of the tunnel, it only took 7 minutes for the bullet train to pass through the tunnel, but we persevered for 3,540 days to overcome this world-class tunnel construction problem. During this period, we experienced geological disasters such as Jiuzhaigou earthquake, landslide, and debris flow. Wang Yuan, project manager of the Chenglan Railway of China Railway Second Bureau, sighed.
In the project area under construction, Wang Yuan is most proud of the "Asia's only and the country's first" single-hole double-line tunnel disaster prevention and rescue station. The rescue station has a three-layer structure of "upper smoke exhaust, middle evacuation, and bottom evacuation (escape)", which is composed of 35 cave groups with a length of more than 3,100 meters, with a large scale and complex structure.
Due to the poor self-stability ability of the surrounding rock of the tunnel, the distance between the various caverns of the disaster prevention and rescue station is very close, and some even have to pass through the main line of the tunnel. According to the different degrees of proximity, the builders adopted comprehensive technical measures such as pre-reinforcement, non-blast excavation, and controlled blasting in different regions, which effectively reduced the construction safety risks caused by the group hole effect.
"This is the hardest tunnel I've ever encountered in my 16 years of railway tunnel construction." Wang Jianjiang, chief engineer of the Chenglan Railway Project of China Railway 16th Bureau, introduced that the most serious section of the tunnel is about 18 meters in diameter and excavated section, which is compressed to only 10 meters wide. Especially during the construction of No. 7 work area, it has encountered the dilemma of less than 7 meters of excavation throughout the year.
In order to overcome the construction problems of large deformation of soft rock, the project team adopted the advanced support system of "rock change and self-change" by analyzing the mechanism of large deformation, deformation law and failure characteristics, and carried out the construction with the rapid ring formation method of large section short steps and the temporary inverted arch method of three steps, and at the same time equipped with large mechanical equipment such as arch installation machine, three-arm rock drilling rig, bolt drilling rig, wet spray manipulator, etc., to control the distance of the initial support closed into a ring at about 25 meters, which reduced the time deformation and span deformation of the surrounding rock, and effectively controlled the tunnel deformation.
"The characteristics of carbonaceous phyllite are broken and soft, a touch to pour, a pinch to crush, when exposed to water into mud, we are around the tunnel like a 'pulverized coal pile', the 10-meter-long grouting anchor pipe is like a hedgehog deep into the rock formation, and the installation of a double-layer HW200 steel arch weighing up to 50 kilograms per meter will be 'locked and grasped' around the rock formation, so that the tunnel 'indestructible'."
According to reports, Desheng tunnel is located in the northwest Sichuan plateau, 2800 meters above sea level, the natural environment and traffic conditions are extremely harsh, since the start of the project, the participants have experienced many serious floods, debris flows, landslides and dangerous rockfalls and other natural disasters, railway ancillary projects destroyed, road damage, construction materials shortage and other dangers. The design unit of China Railway Second Institute, the contractor China Railway Second Bureau and China Railway 16th Bureau are not afraid of hardships and dangers, and strive for the first line of the plateau, especially in the active control of large deformation of soft rock, crossing the active fault zone, intelligent logistics organization and transportation, etc., and have carried out scientific research and research, and gradually improved and optimized, integrated and innovated in the implementation process, and the breakthrough of the Desheng Tunnel has provided valuable experience for the construction of railways in the plateau and mountainous areas of China and even the world.
Sichuan-Qingdao railway is an important part of the mainland's "eight vertical and eight horizontal" high-speed rail network in Lanzhou, Xining to Guangzhou channel, the line starts from Chengdu East Railway Station, through Chengdu City, Aba Tibetan and Qiang Autonomous Prefecture in Sichuan Province, Gannan Tibetan Autonomous Prefecture in Gansu Province, Huangnan Tibetan Autonomous Prefecture in Qinghai Province, Haidong City, Xining City, access to Xining Station, the main line is about 836 kilometers long, the design speed is 200 kilometers per hour, and it is a national I. double-track railway.
Among them, the Qingbaijiangdong to Zhenjiangguan section of the Sichuan-Qingdao Railway will be put into operation on November 28, 2023, and 22 trains have been operated every day since the beginning of this year, with a total of 1.51 million passengers and an average of 11,500 passengers per day. At present, only the section from Zhenjiangguan to Huangshengguan of the Sichuan-Qingdao Railway has not yet been opened to traffic.
It is understood that after the breakthrough of the Desheng tunnel, the construction unit will also carry out the overall track bed pouring, long track laying, four power projects and other construction, Sichuan-Qingdao Railway Zhenjiangguan to Huangshengguan section is expected to be opened to traffic this year.
After the line is put into operation, it will greatly facilitate the travel of the people of all ethnic groups along the line, and is of great significance for promoting economic and social development along the line, maintaining national unity, and serving the large-scale development of the western region to form a new pattern.