Launching reaction force system of ultra-large-diameter TBMs and its design and construction method

With the increasing application of ultra-large-diameter TBMs to meet the demands of large traffic volumes, high conveying capacity, and specific functional requirements, safe and stable provision of reaction forces for ultra-large-diameter TBMs without secondary lining remains a major engineering challenge. Taking the TBM10 excavation section of the 8th bid water conveyance tunnel of the Yangtze-to-Hanjiang Water Diversion Project as the research object, this paper proposed a composite reaction force system of "cast-in-situ lining + anchor bolts (cables)" and established a design-calculation method based on load combination and structural mechanical analysis. The stress and deformation characteristics of the system under the maximum thrust condition were analyzed through a finite element numerical model, and the effectiveness of the system scheme was verified through an engineering example. The results showed that the maximum deformation of the designed composite reaction force system under the action of the TBM launching reaction force was 9.35 mm, only 39% of the specification limit; the maximum stress of the lining was 2.5 MPa, which met the requirements of the specification and allowable stress. On-site monitoring showed that the maximum displacement of the reaction frame during the launching process was 4.3 mm. The system can realize the safe launching of ultra-large-diameter TBMs without secondary lining, and significantly improve construction efficiency and economic benefits. The research results can provide theoretical and engineering references for the design and optimization of reaction force systems for ultra-large-diameter TBM launching under similar complex conditions.