Builders from China Tiesiju Civil Engineering Group install waterproof sealing tapes on precast components for a metro station of Qingdao Metro Line 6 in Shandong province on Friday. [Photo by ZUO QING/FOR CHINA DAILY]

China's first fully prefabricated metro station, meaning all of its main structure, internal structural beams, slabs and columns are precast, has started assembly in Qingdao, Shandong province, for the coastal city's metro line 6 due to run by the end of 2024.

The first phase of Qingdao Metro Line 6, at 30.47 kilometers long with 21 stations, has seen investment by the Qingdao Metro Group and is being built by the State-owned China Tiesiju Civil Engineering Group (CTCE). The assembly is for the Keleshi Station in the city.

Liu Quanwei, chairman and general manager of Qingdao Metro Line 6 Co Ltd, said that within 10 months, the technicians made breakthroughs in assembly and construction technologies, realizing a full prefabrication of beams, slabs, columns and walls in its subway stations.

"The move helped us to take a solid step in greeting a green development mode, achieving the goals of carbon peak by 2030 and carbon neutrality by 2060, while promoting our iterative upgrade in subway construction technology," he said.

Qingdao ran its first metro on Dec 18, 2016 after Qingdao Metro Group Co Ltd was set up in March 2013.

Wang Kaifa, chief engineer of the full prefabrication project, said the new technology can help save four to six months in building a metro station and cut the number of workers by 80 percent.

Meanwhile, it can also help save 800 metric tons of steel, 800 cubic meters of wood, and reduce construction waste by some 60 percent, he said. Statistics showed the new technology can help slash carbon emissions by 20 percent and help in environmental protection, making contributions in achieving carbon peak and carbon neutrality goals, Wang said.

Having started construction in December 2019, the first phase of the Qingdao Metro Line 6 will start at Xintun Road Station and end at Ecological Park Station. It plans to open to traffic at the end of 2024, said Huang Cheng, a CTCE employee.

The innovative technology will be used in six stations of the line's first phase, Huang said.

With the innovation, CTCE technicians not only helped solve the problem in the production, turnover and transportation of large-scale unprestressed concrete components weighing 110 tons, but also independently developed a tooling equipment including a"160-ton intelligent gantry crane plus integral separated trolley," he said.

By using three-dimensional laser scanning and BIM (building information modeling) technologies, they can also control assembly accuracy of prefabricated components within a millimeter, thus achieving precise design, production and assembly.

"The technology helped to break the bottleneck in assembling and constructing the country's first pile-supported station in a systematic way, and filled many gaps in this technology in China," Huang said.

Qingdao Metro Line 6 is an independently-operated demonstration project designated by the National Development and Reform Commission, as well as a model undertaking in helping convert old kinetic energy to new ones in East China's Shandong.

Qingdao Metro Group strives to make Metro Line 6 into an industrial benchmark showing safety, high-quality, innovation, green, wisdom and harmony, Huang said.

Born in November 1950 and with some 23,360 staff members, CTCE is part of the China Railway Group Limited, a centrally-administrated State-owned enterprise.

CTCE currently has 24 engineering companies, five subordinate units, four business operation centers, 10 regional project headquarters, as well as a large group of domestic operating offices and overseas operating offices, said Song Heng, a CTCE official.

At present, its businesses are in nearly 30 provinces, municipalities and autonomous regions across the country. They have also ventured into nearly 20 countries, including Angola, Ethiopia, Mongolia, Indonesia, Panama, Bangladesh and Costa Rica, he said.

CTCE's sales reached 209.6 billion yuan ($32.7 billion) in 2020, with a revenue of 113 billion yuan, Song said. Between 2016 and 2020, the company logged 747.5 billion yuan in sales and recorded a revenue of 404.8 billion yuan.