In the bustling heart of Guangzhou, a city that never sleeps, a silent battle is being waged beneath the streets. As the metro system expands, new tunnels are being bored beneath existing ones, a process known as shield tunneling under-passing. This intricate dance of construction can cause the existing tunnels to settle and deform, posing significant risks to the city’s infrastructure and its inhabitants. But a groundbreaking study led by Xue Ziqian from the College of Civil Engineering and Architecture at Dalian University is shedding new light on how to mitigate these risks, with implications that could reverberate through the energy sector and beyond.
Xue and his team have been delving into the complexities of shield tunneling under-passing, using the Guangzhou Metro Line 22 under-passing Line 3 as a case study. Their work, published in the journal Chengshi guidao jiaotong yanjiu, which translates to Urban Rail Transit Research, is a deep dive into the impact of construction factors on existing tunnel settlement. “The key is to understand how different pressures affect the settlement of the existing tunnel,” Xue explains. “By doing so, we can predict and control the settlement, ensuring the safety and stability of the existing infrastructure.”
The researchers used Midas/GTS NX software to create multiple numerical models, allowing them to analyze the influence of soil chamber pressure and grouting pressure on the settlement of the existing tunnel. Their findings are clear: within a reasonable range, the settlement value of the existing tunnel is negatively correlated with these pressures. In other words, the higher the soil chamber pressure and grouting pressure, the less the existing tunnel settles.
But the implications of this research go beyond just understanding the physics of tunnel settlement. For the energy sector, which often relies on underground infrastructure, this research could be a game-changer. As cities continue to expand and evolve, the need for underground construction will only increase. This research provides a roadmap for how to do so safely and efficiently, minimizing disruption and risk.
Xue’s work has also led to the development of a prediction formula for the settlement of existing tunnels caused by double-line shield tunneling under-passing. This formula, applicable to the Guangzhou area and considering construction factors, is a significant step forward in the field. “It’s not just about predicting settlement,” Xue says. “It’s about providing a tool that can be used in real-world construction projects to ensure safety and stability.”
The lower limits of soil chamber pressure (0.236 MPa) and grouting pressure (0.267 MPa) identified in the study are crucial for construction supervision and protection during shield tunneling closely under-passing. These findings underscore the importance of appropriate pressure management in minimizing disturbance impacts on existing tunnels.
As cities around the world grapple with the challenges of urbanization, this research offers a beacon of hope. It’s a testament to the power of scientific inquiry and the potential it holds for shaping a safer, more sustainable future. For the energy sector, it’s a call to action: to embrace these findings, to innovate, and to build a future that’s not just bigger, but better. The future of urban construction is here, and it’s looking up—even as it delves deeper underground.