In the bustling world of underground construction, ensuring the safety and stability of shield tunnels is paramount. These tunnels, composed of multiple segments, are the lifelines of urban infrastructure, facilitating everything from transportation to energy distribution. However, when these tunnels are under load, relative displacement between segments can occur, posing significant risks. Traditionally, distributed optical fiber sensing technology has been used to monitor strain, but transforming this strain data into meaningful displacement information has been a challenge. Until now.
Maoyi Mao, a researcher at the School of Earth Sciences and Engineering at Nanjing University in China, has been at the forefront of addressing this challenge. In a groundbreaking study published in the journal ‘Deep Underground Science and Engineering’ (formerly known as ‘Diqiu Kexue Yu Gongcheng’), Mao and his team have developed innovative methods to quantify displacement at shield tunnel joints using optical frequency domain reflectometry (OFDR) and discrete element numerical analysis.
The research team conducted laboratory tests to simulate the shear process and center settlement of shield tunnel segments. “Our goal was to bridge the gap between strain data and actual displacement,” Mao explains. “By applying OFDR, we were able to achieve a more precise and quantitative analysis of the deformation at the joints.”
But the innovation doesn’t stop at laboratory tests. The team also simulated the test process numerically using the discrete element method (DEM), a technique that models the behavior of discrete particles. Here’s where things get particularly interesting: the researchers innovatively applied optical fiber, an atypical geotechnical material, for DEM modeling and numerical simulation. This dual approach—combining physical testing with advanced numerical simulation—has yielded promising results.
The findings show that the measured displacement using a dial gauge, the calculated results from the numerical model, and the displacement quantitatively calculated from the optical fiber data all align closely. This convergence suggests that the methods developed by Mao’s team could revolutionize deformation monitoring in shield tunnels.
The implications for the energy sector are significant. Shield tunnels are crucial for the safe and efficient transportation of energy resources. By providing more accurate and reliable deformation monitoring, this research could enhance the safety and longevity of these tunnels, reducing maintenance costs and minimizing the risk of catastrophic failures. “Our methods have the potential to be utilized in engineering applications for deformation monitoring at shield tunnel joints,” Mao states, highlighting the practical benefits of their work.
However, the journey from laboratory success to widespread commercial application is not without its challenges. Mao acknowledges that further calibration and adjustment are needed before these methods can be fully integrated into engineering practices. “We are confident that with additional refinement, our approach will offer a robust solution for monitoring shield tunnel joints,” he adds.
As the construction industry continues to evolve, the need for advanced monitoring technologies becomes increasingly critical. Mao’s research represents a significant step forward in this direction, offering a glimpse into a future where shield tunnels are not just safer but also more efficient and cost-effective. The energy sector, in particular, stands to benefit greatly from these advancements, ensuring that the lifelines of our cities remain secure and reliable.