On July 14, the Hunan Provincial Major Science and Technology Project "Research and Application of Key Technologies for Intelligent Complete Equipment for Super Underground Engineering," led by China Railway Construction Heavy Industry Corporation (CRCHI), passed comprehensive acceptance in Changsha. The expert panel, headed by Gui Weihua, academician of the Chinese Academy of Engineering, concluded that the project has seized the technological high ground of the global underground engineering equipment industry, and that the super underground engineering equipment developed under it has reached the international leading level overall.

The tunnel boring machine (TBM) is the "king" of intelligent complete equipment for underground engineering, and its main bearing is the "heart." Subjected to extremely harsh operating conditions such as ultra-heavy loads, large eccentric loads, and frequent variable loads, the main bearing must meet key performance requirements including high reliability and long service life. Its materials, design, manufacturing, and testing are extremely difficult, placing it at the very top of the large high-end precision bearing industry chain; it has been listed as one of the 35 "bottleneck" (chokehold) key technologies. Foreign companies have long monopolized it, leaving the core components of key equipment subject to the control of others.

To thoroughly implement the major deployment and mission of Hunan Province's "Three Highlands and Four New Missions" strategy and to break through the "bottleneck" technologies affecting the development of enterprises, the industry, and even national construction, CRCHI relied on the Hunan Provincial Major Science and Technology Project, actively responded to the national call, fully leveraged the leading advantages of a TBM OEM, and courageously shouldered the task of tackling "bottleneck" technologies. During the project period, it successfully developed a series of domestic main bearings for machines of 5 meters and below, which passed condition-simulation tests with an equivalent life of more than 10,000 hours and on-site application verification. The products feature outstanding innovations and have demonstrated significant application results, and have already achieved mass production, earning unanimous praise from the expert panel.

During the project, CRCHI established a research and development task force led by Chief Scientist Liu Feixiang, demonstrating the enterprise's principal role in independently tackling core components and targeting the four major key difficulties of the main bearing one by one: it jointly developed high-purity, long-life bearing steel with top domestic steel mills, breaking the fatigue-life bottleneck of traditional main bearing materials; it built proprietary design theories, methods, and dedicated software for main bearings, breaking through the design theory and technology for large low-speed heavy-load bearings; it jointly developed high-efficiency, high-precision hard gear milling technology with leading domestic enterprises, breaking through the bottleneck in domestic large high-end precision gear grinding technology and equipment; and it took the lead in carrying out full-life condition-simulation test verification of main bearings, forming a closed loop of "design-manufacturing-verification" for main bearings and boosting confidence in achieving domestic independent manufacturing of larger-diameter, long-life main bearings.

"Cutting roads through mountains and building bridges over waters." CRCHI has overcome all difficulties, blazed a new path, established a research and development system for key components of high-end underground engineering equipment, taken an important step in breaking through the "bottleneck" technology of TBM main bearings, and provided a strong guarantee for safeguarding the industrial security and high-quality independent development of the tunnel boring machine industry.

"The strong pass is truly like iron, yet now we stride forward from the start." At a new starting point and on a new journey, CRCHI will keep in mind the spirit of the railway soldiers and charge toward the digital, automated, and intelligent technologies for the independent development of larger-diameter underground engineering equipment.