Chongqing- The Chongqing section of the Zhengzhou–Wanzhou high-speed railway is 98% bridges and tunnels, the highest level across China. It is categorized as a subway-type high-speed railway through the mountains. The Chinese people have provided another valuable high-speed railway construction experience to overcome topographical problems and protect the environment.
Put into trial operation in April, the new-generation Fuxing high-speed train runs at about 350 km/h and will be put into official operation soon. With the highest design speed of 350 km/h in China, the Zhengzhou–Wanzhou high-speed railway will shorten the travel time from Chongqing to Beijing and Wuhan from 12 hours and 6 hours to less than 6 hours and 4 hours, which will significantly improve the capacity of railway channels in Southwest China.
Reduction in Train Time from Chongqing to Other Cities. (iChongqing/ Vivian Yan)
Overcoming geographical challenges
China has complex natural conditions with plenty of mountains, especially in southwestern China's Chongqing Municipality, known as the mountain city. The geological structure is complex, and the type of rock and soil is unique, resulting in dense bridges and tunnels.
This line is located in the steep transition area from the third step to the second step of Chinese topography. The terrain and geological conditions of the section are incredibly complex. It starts from the Huanghuai Plain, passes through the Nanxiang Basin, crosses Funiu Mountain, Jingshan Mountain, and Daba Mountain, and traverses eight rivers.
The area along which the high-speed railway passes has geology problems, including karst features, rockfalls, and landslides. The line also passes through the Three Gorges Reservoir and faces the unstable bank slope. The design team has avoided the widely distributed landslides, debris flows, collapses, and karst water in the route design phase to reduce construction risk.
The design team knew that the routing plan was crucial in controlling project investment and reducing construction risks. Since 2008, a group of young people under 30 have participated in the project design. There were no smartphones or navigation maps at that time, and sometimes they would survey the mountains for a whole day without seeing anyone and relying on walking. But finally, they handed out a design to win the recognition of all the experts.
Technological innovation
This line's key and challenging projects include the Wushan Tunnel, the Lesser Three Gorges Tunnel, the Wushan Daning Bridge, the Fengjie Meixi River Bridge, the Tangxi River Bridge, and the Pengxi Bridge.
With a total length of more than 18.9 kilometers, Asia's most extended 350Km/h single-hole double-track tunnel, the Lesser Three Gorges Tunnel, was also born here.
During the tunnel's construction, the primary unfavorable geology is bedding bias pressure, karst and karst water, and dangerous rockfall. The construction team constantly innovates the construction technology and method to overcome these challenges in the construction process.
The Fengjie Meixi River Bridge of the Zhengzhou–Wanzhou railway is a vital project of the whole line, with 688.3 meters. The main span adopts 340 meters reinforced concrete arch. It is the maximum span with a design speed of 350 km/h in a deck-type rigid-frame reinforced concrete arch bridge with a slag-free track globally. The installation of steel arch ribs is the most incredible difficulty.
The Meixi River Bridge is a deck-type rigid-frame reinforced concrete arch bridge. (Photo provided to iChongqing)
"To simplify the operation procedures, we carried out a digital simulation of each step in the installation process of the arch rib segment. We only need one stretch for each arch rib segment, effectively avoiding repeated operations," said Li Guohua, the Fengjie Meixi River Bridge project manager.
"At the same time, we have developed an intelligent monitoring system to monitor and analyze the structural stress and displacement during the construction process and effectively ensure the safety of the arch rib installation," Li added.
The arch rib installation of the Meixi River Bridge. (Photo provided to iChongqing)
Li recalled that installing the last section before the arch rib closure was the most memorable part. The more arch bridge installed, the higher the construction risk is. Because during the installation process, the stress and the line shape of the arch rib of the whole system are constantly changing. Like blocks, the higher, the greater the risk of collapse. Despite the last segment weighing 133 tons, they finally completed the installation of all parts and delivered a perfect solution.
Ecological protection
Nearly 100 important environmentally sensitive areas exist along the railway, including 33 nature reserves, nine scenic spots, 15 forest parks, and national key protected plants. The design team has avoided the Shennongjia National Nature Reserve and runs into the Three Gorges Reservoir to protect the environment.
During the design phase, the design team selected mountains away from the Yangtze River, stacking the tunnel debris in centralized and taking measures for greening and reclamation. They have increased the span of the bridge to reduce setting piers in the water to protect the water and fish. Besides, they have avoided the road construction method of high filling and deep excavation to keep the natural environment as original as possible.
The Wushan Station of Zhengzhou–Wanzhou high-speed railway is located in the Lesser Three Gorges, a famous national 5A-level tourist scenic spot. The station is the only transportation center integrating a high-speed railway, expressway, airport, and tourist harbor in China.