The world's first in-situ diameter-adjustable tunnel boring machine was rolled out at an equipment company in Foshan, Guangdong province, on Tuesday, representing a significant breakthrough in the field of rail transit construction in China.

The machine, manufactured by China Railway Huatun Joint Heavy Equipment Co., one of the leaders in research and manufacturing of tunnel boring machines, enables the integrated construction of both section and rail station tunnels, according to Liu Zhicheng, Party chief and chairman of Guangzhou Metro Group.

"The machine addresses issues associated with traditional methods, such as ground excavation, construction interruptions and site occupation, making it particularly suitable for construction in densely built, traffic-heavy and demolition-challenging urban core areas," said Liu.

Construction of urban rail transit station typically relies on open-cut and underground excavation methods, with section tunnels needing to be constructed independently.

"The separated construction process often results in significant environmental disturbance, low resource efficiency and extended construction periods," said Liu.

The Variable Diameter No 1 tunnel boring machine will first be used in an intercity rail project at the Guangzhou Railway Station, implementing diameter adjustment and constructing the station tunnels after tunneling to the station area, according to Liu.

The machine can freely adjust its diameter, innovatively achieving a continuous construction method of building one station with two tunnels, according to Liu.

"Initially, the machine tunnels through section tunnels with a smaller diameter. Upon reaching the station location, it expands in place to excavate a wider tunnel for the station platform level," said Liu.

After completing the station section, the machine reduces its diameter again to continue tunneling toward the next section, all without the need to dismantle the machine or set up additional working shafts.

"The method using the diameter-adjustable tunnel boring machine significantly streamlines the construction process," he said.