In a significant advancement for urban infrastructure, researchers have unveiled critical insights into the dynamics of overlapping shield tunnels with small curve radii. This study, led by Xu Zhang from the School of Civil Engineering at Inner Mongolia University of Science and Technology, addresses a pressing challenge in subway construction, particularly as cities expand and the demand for efficient transport networks grows.
The research focuses on a specific project in Beijing, where an upper tunnel partially overlaps a lower one, resulting in complex uplift issues for the existing structure. The findings reveal that the maximum uplift displacement occurs in the first segment of the shield, with this displacement increasing as the horizontal space between the tunnels widens. “Our simulations and on-site monitoring have shown that while individual reinforcement measures can help, it is the combination of interlayer soil grouting and steel supports that truly stabilizes the structure,” Zhang explained.
The implications of this study are profound for the construction sector. As overlapping tunnels become more common in urban planning, understanding the stress characteristics of steel supports and the uplift patterns of tunnel linings is essential for ensuring safety and structural integrity. The research demonstrates that when both soil grouting and steel bracing are used together, the uplift of the tunnel lining remains within a maximum threshold of 4.87 mm, meeting deformation control requirements. This is a crucial finding for engineers tasked with designing safe and reliable underground transport systems.
Zhang emphasized the importance of these findings for future developments in tunneling projects. “By enhancing soil strength and controlling uplift deformation, we can significantly improve the stability of existing tunnels. This not only protects the infrastructure but also reduces potential costs associated with repairs and delays,” he stated.
The study also highlights the relationship between the deformation of circumferential supports and tunnel segments, indicating that effective control of segmental uplift is achievable through the application of H-shaped steel supports. As urban areas continue to densify, the ability to manage the stresses associated with overlapping tunnels will be pivotal in maintaining safe and efficient transportation networks.
As cities evolve and the complexity of underground construction increases, this research, published in ‘Deep Underground Science and Engineering’, offers a valuable reference point for engineers and planners alike. By understanding the mechanics behind overlapping shield tunnels, the construction industry can better navigate the challenges posed by modern urban infrastructure demands.
For more information about Xu Zhang’s work, visit School of Civil Engineering Inner Mongolia University of Science and Technology.
