In the heart of Nanjing, a critical intersection of urban development and energy infrastructure has been under the microscope, with implications that could reshape how cities worldwide approach underground construction. Researchers, led by WEI Yishan of the Nanjing Branch of CCCC Third Harbor Engineering Co., Ltd., have been scrutinizing the delicate dance between shield tunneling and existing oil pipelines, particularly in challenging silty clay strata. Their findings, published in *Chengshi guidao jiaotong yanjiu* (Urban Rapid Rail Transit), offer a roadmap for safer, more controlled construction in densely populated areas.
The study zeroes in on the Qixia Mountain Depot access lines of Nanjing Metro Line 6, where twin shield tunnels navigate a labyrinth of underground pipelines. “The key challenge here is to ensure the integrity of these pipelines while advancing the tunnel,” WEI explains. “A misstep could lead to catastrophic consequences, including pipeline damage and potentially hazardous oil-gas leaks.”
The research reveals a nuanced pattern of pipeline deformation during shield tunneling. Initially, the pipeline experiences uplift due to soil unloading during excavation. This is followed by a period of subsidence induced by synchronous grouting, where the volume of grout injected plays a pivotal role. “The greater the grout volume, the more pronounced the subsidence,” WEI notes. The pipeline then undergoes a second uplift before stabilizing, a process that underscores the complexity of underground dynamics.
Ground deformation is equally intricate, influenced by both stratum loss and the pressures exerted by the tunneling process. “Land subsidence and surface uplift are not just theoretical concepts; they have real-world implications for construction safety and efficiency,” WEI emphasizes. The study highlights that the maximum pipeline deformation observed was 16 mm, while ground deformation peaked at 10 mm—both within controllable limits, but critical to monitor.
For the energy sector, these findings are a game-changer. As cities expand and underground infrastructure becomes increasingly congested, the ability to predict and control deformation during tunneling is paramount. “This research provides a framework for mitigating risks and ensuring the safety of both new and existing infrastructure,” WEI says. “It’s not just about building tunnels; it’s about safeguarding the lifelines of our cities.”
The implications extend beyond Nanjing. As urbanization accelerates globally, the need for sophisticated construction techniques that minimize disruption and maximize safety will only grow. WEI’s work offers a blueprint for future developments, emphasizing the importance of real-time monitoring and adaptive construction practices.
In an era where urban development and energy infrastructure must coexist harmoniously, this research shines a light on the path forward. By understanding and controlling the intricate interplay between tunneling and underground pipelines, cities can continue to grow—safely, efficiently, and sustainably.