A CREC4 employee checks construction work at the Qingdao Metro Line 6 in Shandong province on April 27. [Photo by Guo Fangming/For China Daily]

China's first fully prefabricated metro station, meaning all of its main structure, internal structural beams, slabs and columns are precast, completed assembly on April 27 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, is financed by the Qingdao Metro Group and is being built by the State-owned China Railway No 4 Engineering Group Co Ltd (CREC4). The completion this time is at Keleshi Station.

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

"The move helped us to achieve 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, director of the CREC4 project, said the new technology can save four to six months in building a metro station and cut the number of workers by 80 percent.

It can also save 800 metric tons of steel and 800 cubic meters of wood, and reduce construction waste by some 60 percent, slashing carbon emissions by 20 percent, he said.

The innovative technology will be used in six stations of the line's first phase, which started its construction in December 2019, said Wang Hui, a CREC4 employee.

With the innovation, CREC4 technicians also independently developed 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 control the assembly accuracy of prefabricated components within a millimeter, achieving precise design, production and assembly.

Established in November 1950, CREC4 is part of China Railway Group Ltd, a centrally administrated State-owned enterprise.

CREC4 realized a value of 236.6 billion yuan ($37.1 billion) in newly signed contracts in 2021, said its chairman, Liu Bo, adding that it aims to gain a value of 270 billion yuan in newly signed contracts and a business income of 120 billion yuan in 2022.