Recently, at the construction site of the Chengdu North Renovation Line Section B utility tunnel project undertaken by CCCC Second Harbor Engineering Co., Ltd., a central enterprise in Hubei, as the dedicated tunnel assembly boring machine successfully jacked through, the first ring of the underground utility tunnel assembled into a ring using precast components provided by Chengdu Chengtou Technology Co., Ltd., in which CCCC Second Harbor Engineering holds an investment stake. This marks the birth of a brand-new underground utility tunnel construction technology in China that adopts segmented prefabrication and boring machine assembly integrated construction for the first time, advancing urban utility tunnel construction into the modular era.
　　It is understood that the prefabrication rate of the main structure of the utility tunnel in this project can reach 100%, and five patents independently developed by CCCC Second Harbor Engineering around structure, equipment, and construction methods have been adopted.
　　The new utility tunnel innovatively adopts a “horseshoe-shaped” cross-section structure, which is more reasonable in force distribution than the traditional rectangular cross-section structure. Not only are the component structural dimensions smaller, but by adding vertical partition walls, a single compartment can be transformed into double compartments, and double compartments into triple compartments, which is conducive to the industrialized production of segment prefabrication. The joints of the new utility tunnel adopt water-stop rubber seals for waterproofing, and the design service life can reach 100 years. The weight of the entire ring of the utility tunnel is reduced by 40% compared with the traditional rectangular segmental precast utility tunnel structure, greatly reducing the restrictions and costs of transportation and installation.
　　At the same time, the precast assembled underground tunnel dual-mode boring machine is also used for the first time in China. It draws on the construction technical principles of shield tunneling and pipe jacking, and integrates functions such as soil excavation, mobile support, segment installation, and backfilling. The equipment can be applied to a burial depth of up to 8 meters, fully meeting the construction requirements of general urban utility tunnels. Compared with traditional cast-in-place with foundation pit support, the new equipment and construction method improve efficiency by more than twice, reduce construction workers by more than half, save 5% of the project cost just by eliminating permanent foundation pit support, and greatly reduce construction waste. It has little impact on road traffic and the environment, and safety risks are also significantly reduced.
　　With the three-pronged approach of new structure, new equipment, and new construction method, the new utility tunnel technology of CCCC Second Harbor Engineering has achieved factory assembly-line prefabrication and mechanized rapid assembly, filling the gap in the application of prefabricated segment assembly for utility tunnels in China, breaking through the constraints of low construction efficiency, high cost, and great traffic impact of traditional utility tunnel construction, conforming to the development direction of intelligent construction and green environmental protection in the construction industry, and powerfully promoting the progress of prefabricated construction technology for underground engineering, which will have a revolutionary impact on future urban municipal comprehensive construction.