Recently, in the Second Industrial Park of China Railway Construction Heavy Industry Group Co., Ltd. (hereinafter referred to as CRCC) in Changsha, Hunan Province, multiple "large iron rings" with diameters ranging from 3 meters to 8.6 meters are being processed and manufactured in a factory building with the code "197". These "big iron rings" are called main bearings and are the "heart" components of shield tunneling machines. It is the only component that cannot be replaced during the service period of the shield tunneling machine, and needs to face extreme harsh working conditions such as overload, large eccentric load, and frequency variable load of the shield tunneling machine. After the main bearing is formed, if it is damaged, the shield tunneling machine worth billions of yuan will face the danger of scrapping, and the cost of the entire project will also increase exponentially. The manufacturing of the main bearings of shield tunneling machines was once a difficult problem that constrained the development of China's industry. "To achieve high-level technological self-reliance and self-improvement, it is necessary to carry out more innovative research and break through key technological difficulties." Liu Feixiang, a National People's Congress representative and chief scientist of China Railway Construction Heavy Industry, said that China's shield machine industry not only needs to achieve global leadership in overall machine technology and the largest market share, but also needs to achieve independent and controllable key systems. In recent years, China Railway Construction Heavy Industry has relied on the advantages of the new national system, strengthened the collaborative innovation of government, industry, academia, research and application, and carried out independent research and development on key components of shield tunneling machines such as heavy-duty bearings, control systems, reducers, hydraulic pump motors, etc., achieving complete independent control of key components. "The service life and reliability of main bearings are constrained by various key factors such as materials, design, and manufacturing technology, and the difficulty of development doubles with the increase of size." When it comes to the weak links in China's shield tunneling machine industry, Liu Feixiang has a deep understanding. "In the past, foreign enterprises not only hindered us in technology, but also increased the price increase year by year." How difficult was it to develop main bearings? Liu Feixiang summarized four major difficulties: material difficulty, design difficulty, manufacturing difficulty, and experimental difficulty. Taking the ultra large diameter main bearing as an example, its raceway diameter can reach several meters, and its flatness should be less than 20 microns, which is equivalent to one-fifth of the thickness of an A4 paper. The straightness should be less than 8 microns, only one tenth of the thickness of a hair. This processing and manufacturing process is no different from carving characters on hair and carving flowers on rice grains. In July 2019, Liu Feixiang led the establishment of a research and development team, collaborating with upstream and downstream enterprises and higher education institutions to explore hundreds of materials and processes, and conducted field experiments to analyze tens of thousands of sets of data. In October 2023, the team successfully developed the main bearing of a 8.61 meter diameter shield tunneling machine. This marks that China has completely conquered and independently mastered the key core technology of the entire process of material, design, manufacturing, and testing for the main bearings of shield tunneling machines, giving domestic shield tunneling machines a full series of "Chinese hearts". While continuously conquering core technologies, China Railway Construction Heavy Industry is accelerating its digital transformation. Through digital empowerment, it has innovatively created a digital twin system for shield tunneling machines, unleashing the power of "digital intelligence" in major industries. "This system collects real-time engineering construction data, such as the operation data of various components of shield tunneling machines, underground environmental data, etc. After system analysis, it remotely and online helps technical personnel make operational decisions for current models in real time, and provides big data support for the optimization and upgrading of next-generation products." Liu Feixiang said that digital twin technology breaks the boundary between virtual and real, avoiding the problems that may arise from manual on-site surveys in the past