In recent years, the strength of China's infrastructure can be well-known in the world, including the $32 billion China-Pakistan Economic Corridor, the $13.1 billion Nigerian high-speed railway, and the $30 billion Bangladesh Padma Bridge and other large-scale projects. The construction was started amid doubts about foreign infrastructure, and finally China was recognized by the international community for its smooth delivery.

Yunnan Dari International Railway Project

At present, there is such a large-scale project that catches the eyes of the Chinese people, but American experts scoff at the project, believing that it is absolutely impossible for China to do. This project is the Yunnan-Da-Rui Railway. The railway is 330 kilometers long. It is a joint-venture construction of the Ministry of Finance, with an investment of 25.73 billion yuan and a design speed of 140 kilometers per hour. As of 2018, the Dali Railway starts from Dali Station and ends at Ruili Station, with Yangbi Station, Yongping Station, Baoshan Station, Longling Station, Mangshi Station and other county-level and prefecture-level middle stations along the way. The proportion of bridges and tunnels on the entire Dali-Ruizhou railway reaches 75%, and the proportion of bridges and tunnels from Dali to Baoshan reaches 86.5%. The construction is extremely difficult. On December 28, after 6 years of fierce battles, new progress was made in the construction of Baoshan Tunnel, a key project of the Dalui Railway, undertaken by China Railway Fifth Bureau. A total of 15,597 meters of tunnel excavation have been completed. In January 2022, the Dabao section of the Yunnan Da (Li) Rui (Li) Railway, an important part of the China-Myanmar International Corridor, was connected across the entire line.

This line is an important project in China's "Mid- and Long-Term Railway Network Planning" to improve the road network layout and western development. The project originally planned to open in five years took 12 years, but it was delayed by nearly twice due to a tunnel project. duration. However, on this 330-kilometer-long railway, there is a tunnel with a length of only ten kilometers. This stumped China, which is called the world's infrastructure madman. This is recognized by the world's railway construction experts as the most difficult. The Dazhushan Railway Tunnel called hell mode, from the construction time of this tunnel, it can be seen that the construction of this tunnel is by no means simple. So what kind of tunnel can the infrastructure maniac China have to admit, this is a very difficult tunnel?

Dazhushan Tunnel Difficulty Unprecedented

In fact, the difficulty of this tunnel is closely related to the geographical location it passes through. The Dazhushan Tunnel is actually located on the Hengduan Mountains in China. One of the youngest mountain groups in the world formed by the extrusion of plates. Mountains, one after another; peaks, one peak after another, not only the terrain is very rugged, but basically composed of parallel mountains one after another, and more importantly, this The region is also the origin of many large rivers such as the Nu River, Lancang River and Dadu River in China, which means that the region has very rich water resources. When there are a lot of fissures, the rainwater brought by rivers and rainfall will enter the ground and become groundwater, and the abundant groundwater resources in this area are an important factor that makes the construction of the Dazhushan Tunnel very difficult. The Dali-Rui Railway is the first railway to cross the Hengduan Mountains. The Dazhushan Tunnel is located in Baoshan City, the section from Dali to Baoshan of the Dali-Rui Railway, with a total length of 14,484 meters. Bad geology and major risks such as fault fracture zone, intrusive body alteration zone, and karst are known as "the most difficult railway tunnel to excavate".

The occurrence of water gushing and mud intrusion on the excavation surface of the tunnel is the most worrying situation for the construction personnel. The Dazhushan Tunnel drilled holes in the bean curd slag, and the most worrying situation has become the norm. The construction personnel frequently fought with the sudden gushing of cement slurry. In August 2009, the tunnel was excavated to the core section of the most difficult Yanziwo fault, with a distance of 156 meters. It took a full 26 months to excavate, and the average daily excavation was only about 20 cm. Since the tunnel construction started in 2008, under the organization of Yunnan-Guizhou Railway Yunnan Company, the builders of China Railway No. 1 Bureau crossed 6 geological fault zones, and successively built 7 pumping stations and 56 large water pumps in order to discharge up to 220,000 cubic meters of water per day. Relay, such a single-day inflow of water can fully store 88 standard swimming pools with a length of 50 meters. In addition to "water depth", there is also "fiery". The long-term temperature in the high ground temperature section of the tunnel is about 40°C and the humidity is above 85%. The construction unit transports ice cubes to the excavation surface of the tunnel for many years to cool down. Each excavation surface needs 12 tons of ice cubes every day, and the construction personnel are rotated every 3 hours. once. "Deep water" and "hot" are just two of the many puzzles. The maximum burial depth of the tunnel is 995 meters, and the longitudinal slope in the tunnel is designed as a "ren"-shaped slope with a maximum longitudinal slope of 23.5‰. In particular, it has successfully passed through the 1270-meter coal-measure stratum containing gas.

Different from other long tunnels, the Dazhushan Tunnel can only be excavated from the entrance and exit alone, without auxiliary construction conditions such as shafts and inclined shafts, and the maximum excavation length is 8.3 kilometers. In order to solve the problems of construction waste, ventilation and drainage caused by the single-headed excavation of the tunnel entrance and exit, the construction personnel built a 14,190-meter-long flat guide 30 meters on the left side of the main tunnel. The flat guide will also be used for disaster prevention and evacuation after operation. channel of rescue.

During a construction process, workers drilled and blasted the fault, resulting in a 20-centimeter-diameter breach on the face. Even with such a micro-flaring, the mud-water mixture poured out of it. In just one hour, the 4-meter-high engineering equipment in the tunnel was submerged, and the entire 400-meter-long tunnel was directly filled in a few hours. Similar incidents occurred during the excavation of the entire tunnel. It did not happen by accident. Almost every few meters, the engineering team found a crack in the tunnel that spewed out a large amount of groundwater. The highest recorded water spout even reached 12,200 cubic meters per hour, which is almost equivalent to the amount of water sprayed from the tunnel. A river was dug out of it.

Faced with such a situation, China, on the one hand, has built a 5-stage pumping station in the tunnel to conduct pumping operations 24 hours a day, so that a rushing waterfall is formed outside the tunnel. Research on the engineering method of the water storage section, and finally came up with a solution: high-pressure dynamic water section diversion, ultra-high-pressure polymer grouting and pipe shed grouting and water-blocking reinforcement scheme, successfully achieved this solution that experts all over the world believe almost Impossible successful construction tasks. Liu Xiaorong, the executive deputy commander of the Dari-Rui Railway Project of the China Railway First Bureau, introduced that there were two small landslides in the last one or two hundred meters, because the surrounding rock at that time was diabase, and the self-stability was very poor, and it would become muddy. Since April, we have resumed work and production in a rapid and orderly manner. More than 1,500 people have worked hard day and night to press the "fast-forward button" for construction to achieve the smooth completion of the entire tunnel. It can be said that the engineers spent 12 years in exchange for the railway. The tunnel, which passengers can pass through in only seven minutes, not only shows China's strong industrial and engineering strength, but also shows the determination of the Chinese people to never back down and resolutely overcome the great difficulties.

Yunnan-Da-Rui Railway activates Southwest China's economy

The construction of the project led a German expert to confront the professors present at an international seminar and say that China has the best engineering university, and Chinese students do not need to study abroad at all. This is the affirmation of the Chinese infrastructure construction crowd. China's infrastructure construction has conquered the world in an instant, and it has also slapped Americans in the face. The railway goes down from Dali along the right bank of Xi'er River, crosses Yangbi River, Yinjiang River, Lancang River, passes through Dazhu Mountain to Baoshan City, then passes through Nujiang River and Gaoligong Mountain, and finally arrives at Ruili. After the completion and opening to traffic, the travel time from Dali to Ruili will be shortened from about 7 hours now to about 3 hours, which will promote the economic and social development of the regions along the route, improve the level of Yunnan's opening to the outside world, build a new channel for the Belt and Road Initiative in Southeast Asia, stabilize the southwest border, and promote The exchanges and cooperation between China and South Asian and Southeast Asian countries are of far-reaching significance.

Zeng Jin, deputy commander of the Dari-Rui Railway Headquarters of the Yunnan Company of Yungui Railway, said that up to now, 29 of the 44 tunnels on the Dali-Rui Railway have passed through; 90% of the roadbed project has been completed from Dali to Baoshan, and 84% of the bridge project has been completed. %; In the section from Baoshan to Ruili, 81% of the roadbed project and 75% of the bridge project have been completed. Since the resumption of work and production, 105% of the planned bridge, roadbed and tunnel project has been completed. The Yunnan-Darui railway project is expected to be put into operation in December 2022.Editor/XingWentao