In the heart of Chongqing, a city known for its dramatic topography and bustling metro system, a groundbreaking study is reshaping the way engineers approach large-span mined station tunnels. Huapeng Yu, a leading expert from China Railway Construction Chongqing Investment Group Co., Ltd., has published a pivotal analysis in the journal *Chengshi guidao jiaotong yanjiu*, which translates to *Urban Rail Transit Research*. The study, titled “Analysis of Surrounding Rock Damage in Large-span Mined Metro Station Tunnels with Different Rise-span Ratios under Sandy Mudstone Conditions,” delves into the intricate relationship between rise-span ratios and the structural integrity of metro tunnels.
Yu’s research focuses on Kuangjiatang Station on Chongqing Rail Transit Line 24, a critical hub in the city’s extensive metro network. By establishing a 3D numerical model, Yu simulated the displacement and deformation of large-span structures, providing invaluable insights into the behavior of surrounding rock under various rise-span ratios. “The vertical displacement caused by vault settlement gradually increases as the rise-span ratio decreases, while the horizontal displacement of tunnel sidewalls gradually decreases with a reduction in the rise-span ratio,” Yu explains. This finding is crucial for understanding how different structural designs impact the stability of metro tunnels in sandy mudstone conditions.
The study reveals that the failure approach index, a key indicator of structural integrity, varies significantly around the station, ranging from 0.106 to 0.783. Notably, the maximum failure approach index is located in the surrounding rock near the sidewalls. Yu’s analysis shows that when the rise-span ratio is between 1.0:2.0 and 1.0:2.4, the maximum failure approach index decreases rapidly. However, when the ratio is between 1.0:2.4 and 1.0:3.0, the decrease slows down, and the proportion of surrounding rock with a failure approach index ≥0.7 remains relatively small.
One of the most compelling findings is that the maximum horizontal depth of surrounding rock exhibiting a failure approach index ≥0.7 exhibits a monotonic decrease followed by a sudden increase as the rise-span ratio decreases. This intricate behavior underscores the complexity of optimizing rise-span ratios for large-span structures. Yu’s research concludes that the optimal rise-span ratio for the large-span structure in the study area is 1.0:2.8, at which the stress condition of the surrounding rock structure is most favorable.
The implications of this research are far-reaching, particularly for the energy sector, where the stability of underground structures is paramount. As cities continue to expand and metro systems become increasingly complex, understanding the optimal rise-span ratios for large-span tunnels will be crucial for ensuring the safety and longevity of these critical infrastructure projects. Yu’s work not only provides a scientific foundation for future developments but also highlights the importance of continuous research and innovation in the field of urban rail transit.
Published in *Urban Rail Transit Research*, Yu’s study serves as a beacon for engineers and researchers seeking to push the boundaries of what is possible in metro construction. As the demand for efficient and reliable public transportation continues to grow, the insights gleaned from this research will undoubtedly shape the future of urban infrastructure, ensuring that our cities remain safe, sustainable, and connected.