Chongqing- Can you imagine setting a coin upright on a train compartment traveling 350 km/h through a section of rail that's 98% bridges and tunnels? You can realize this fantastic dream on the Chongqing section of the Zhengzhou-Wanzhou high-speed railway.

To make passengers experience the ultimate comfort, an ingenious Chinese team has kept the deviation of millions of sleepers and pads within 0.2 mm, equivalent to the width of three human hairs.

Great technical difficulty

The Chongqing section of the Zhengzhou-Wanzhou high-speed railway operates at 350 km/h. A high-speed railway's safety, fast and stable operation, and passengers' smooth experience in the compartment require exceptionally high rail construction standards.

After the foundation engineering was completed, the fine adjustment team adopted the CP III absolute measurement method to measure the track size, elevation, and other data according to the deviation data to develop an acceptable adjustment plan. Then, the fine adjustment team can conduct static fine adjustment. It is necessary to meet two proper adjustment requirements at the same time. The single deviation value of 7 data indicators, including track gauge, level, triangle pit, and track direction, should be controlled within 0.2 mm. The total track quality index (TQI) of 7 indexes should be contained within 1.3 mm.

"There are different requirements for fine adjustment at different speeds. At 200 km/h, one or two times fine adjustments are required. However, at 350 km/h, the number of fine adjustments increases to five or six," said Hu Zehao, assistant engineer of Line Maintenance Technology Center of Chongqing Engineering and Electricity Section, China Railway Chengdu Group Co., Ltd.

The ingenuity of China's high-speed railway

The total length of the high-speed railway from Wanzhou North to Wushan is about 180 kilometers, and the dual-track length is about 360 kilometers. The fine adjustment team has divided 360 kilometers into sections, each section with 300 meters. They need to adjust each section 4 to 5 times. They have changed six types of rubber pads from 2 mm to 8 mm and 16 gauge aprons from 1 mm to 8 mm to achieve the best coupling between rail parts. The team then used track detectors to check the eight indicators until they were within the deviation standard.

"In the beginning, we could only adjust tens of meters a day because we had to be familiar with all the components on the rails. After half a month's exploration and summary, we could pick up speed," Hu added.

"The track width is 1,435 mm, and each of the eight parameters is controlled within 0.2 mm. It's the width of three human hairs. The original technical deviation requirement is 1 mm; the larger the deviation, the more bumpy passengers will feel. To ensure a comfortable ride for passengers, we have increased the accuracy to 0.2 mm," Hu explained.

There are over 600,000 sleepers, over 1.2 million pads, and 2.4 million gauge baffles on the rail. To achieve this 0.2 mm deviation, this ingenious group of men carved every plate and inch of rail from July 2021 to April 2022. They get up at 6 am daily, wear headlights, and leave work at 10 pm, working 16 hours straight in the dark tunnel, bending over hundreds of times a day. Such ingenuity shows China's determination to lead the world in the field of high-speed rail.