In the bustling world of urban infrastructure, a groundbreaking study has emerged that could reshape how we approach the construction and seismic safety of large-diameter city railway shield tunnels. Led by ZHANG Xiaobin from Shanghai Shen-Tie Investment Co., Ltd., the research delves into the seismic performance of machinery-constructed link passages with eccentric openings, an area previously unexplored in the engineering of 9-meter-class tunnels.
The study, published in *Chengshi guidao jiaotong yanjiu* (translated to English as *Urban Rail Transit Research*), utilizes advanced finite element software, Plaxis 3D, to simulate the seismic performance of main tunnel-link passage structures under horizontally incident seismic waves. This innovative approach provides critical insights into the behavior of these structures under earthquake conditions, which are becoming increasingly relevant as cities expand and face more frequent seismic activity.
ZHANG Xiaobin explains, “Our findings reveal significant variations in the axial force and bending moment at the joint section of the combined structure. Under seismic waves with a peak acceleration of 0.1g, the maximum axial force increases by 53% compared to the initial condition, and the bending moment increases by a staggering 410%.” These findings highlight the critical need for robust design and construction methods to ensure the safety and stability of urban railway systems.
The research also shows that the internal force variations at the link passage mid-section are relatively minor, with a maximum increase amplitude of less than 30%. However, the constraint effect of the main tunnel significantly reduces the absolute displacement and convergence deformation at the main tunnel-link passage junction compared to the mid-section. “Under seismic waves with a peak acceleration of 0.2g, the additional convergence deformation at the joint section is -0.25 mm, while at the link passage mid-section it is 0.59 mm,” adds ZHANG.
One of the most intriguing findings is the inclined elliptical deformation experienced by the link passage mid-section under horizontally incident seismic waves. The maximum displacement points are located at the 45° and 135° positions of the upper semicircle, with an inclined additional convergence deformation of 1.56 mm. This insight could lead to more precise engineering designs that account for such deformations, enhancing the overall safety and longevity of urban railway systems.
The commercial implications for the energy sector are substantial. As cities continue to grow and expand, the demand for efficient and safe urban transportation systems will only increase. This research provides a foundation for developing more resilient and cost-effective construction methods, ultimately benefiting both the construction industry and the energy sector. By understanding the seismic performance of these structures, engineers can design tunnels that are not only safer but also more economical to build and maintain.
ZHANG Xiaobin’s work is a testament to the power of advanced numerical simulations in solving real-world engineering challenges. As urbanization continues to accelerate, such research will be crucial in ensuring that our infrastructure can withstand the forces of nature while meeting the demands of a growing population. The findings from this study are poised to shape future developments in the field, driving innovation and ensuring the safety of urban railway systems worldwide.