Yesterday, the reporter learned that following the "Yangming" shield, another major technological innovation has been launched by Ningbo Rail Transit. Ningbo Rail Transit recently held a project approval meeting for "Key Technologies for Mechanical Connection Gallery Equipment and Design & Construction" (abbreviated as "T"-joint tunnel technology). The expert panel fully affirmed the technical route and plan of the project team and agreed to approve the project. 
        In November 2016, the "Yangming" tunnel was completed on the access line of Phase I of Rail Transit Line 3, becoming the first rectangular shield tunnel for urban rail transit in China and the world's largest cross-section rectangular shield tunnel. The "T"-joint tunnel technology is mainly aimed at solving specific problems in underground space connectivity, enabling better interconnection of underground space islands.
　　With the acceleration of urbanization, underground spaces are facing high-intensity development. Currently, underground space systems with various functions such as rail transit trunk lines, municipal utility tunnels, commercial parking lots, commercial complexes, civil air defense projects, and deep drainage tunnels have taken shape. However, the lack of connectivity between these underground spaces has turned them into "space islands."
　　Can these underground spaces be interconnected like the ground roads that extend in all directions? At present, the connectivity of underground spaces in Ningbo is basically achieved using the freezing method combined with the mining method. However, this secondary excavation construction has problems such as high cost.
　　How to find an economical, safe, and fast construction method to achieve underground space connectivity? Zhu Yaohong, a professor at Ningbo University, deputy commander and chief engineer of the Municipal Rail Transit Engineering Construction Headquarters, said that Ningbo Rail Transit, based on the refined construction needs of connection galleries, has carried out research and development of the "T"-joint technology for shield tunnels, aiming to systematically solve the technical challenges of underground engineering network connectivity. This technology is expected to be applied in the construction of Ningbo Rail Transit Line 4.
　　In the future, where else will the "T"-joint tunnel technology be applied? Zhu Yaohong said that the technology is extensible and can be promoted and applied in shield tunnel connection projects in transportation, municipal, and water conservancy engineering.