In the bustling world of urban infrastructure, the construction of city railways is a complex dance of engineering prowess and technological innovation. A recent study published in *Chengshi guidao jiaotong yanjiu* (Urban Rail Transit Research) sheds light on the mechanical response analysis of city railway machinery method link passages under eccentric opening conditions, offering valuable insights for the construction industry.
The research, led by LI Yitao of China Railway Shanghai Design Institute Group Co., Ltd., focuses on the application of the machinery construction method for link passages in 9-meter-class diameter shield tunnels, a size typically used in metro projects. This method has been widely applied in smaller 6-meter-class diameter tunnels, but its use in larger tunnels has been limited due to a lack of engineering practice cases and research.
LI Yitao and his team established a three-dimensional load structure model of the main tunnel and link passage to analyze the impact of link passage construction on the main tunnel structure. They considered varying conditions of burial depth, soil parameter, and shield machine thrust, examining deformation, axial force, and bending moment of special segments under different operating conditions.
“The additional deformation caused by the construction of the link passage is influenced by both the burial depth and the thrust of the shield machine,” explains LI Yitao. “When the burial depth is large, the link passage construction will increase the convergence deformation of the main tunnel; when the burial depth is small, it reduces the convergence deformation. An increase in shield machine thrust further reduces the convergence deformation of the main tunnel.”
The study also found that changes in the main tunnel internal forces are mainly concentrated in the steel segment sections of the three-ring special segments. “The axial force and bending moment at the arch waist of the semi-open segment significantly increase, with the maximum occurring under operational conditions, which requires special attention during design,” notes LI Yitao. In contrast, internal force changes in the concrete segments were relatively minor.
This research has significant implications for the construction industry, particularly in the energy sector where large-diameter shield tunnels are increasingly used. By understanding the mechanical responses of these structures under various conditions, engineers can design more efficient and safer tunnels, reducing costs and improving project outcomes.
As urbanization continues to grow, the demand for efficient and reliable city railways will only increase. This study provides a crucial step forward in the development of large-diameter shield tunnel construction methods, paving the way for more innovative and sustainable urban infrastructure projects.
In the words of LI Yitao, “This research not only advances our understanding of the mechanical responses of large-diameter shield tunnels but also offers practical solutions for engineers and designers in the field.” As the construction industry continues to evolve, such insights will be invaluable in shaping the future of urban infrastructure.