In the bustling world of urban infrastructure, the construction of metro stations is a complex dance of engineering prowess and scientific precision. A recent study, led by WANG Zhaobing from China Construction Third Engineering Bureau Ltd., based in Wuhan, China, has shed new light on the challenges and optimal strategies for metro station excavation using the PBA (pile-beam-arch) method. The findings, published in ‘Chengshi guidao jiaotong yanjiu’ (Urban Rail Transit Research), could reshape how we approach underground construction, with significant implications for the energy sector and beyond.
The study delves into the group-tunnel effects and mechanical characteristics of ingates during the bidirectional excavation process of metro stations. Using FLAC3D software, WANG and his team created a three-dimensional numerical model to simulate the construction process. Their goal? To identify the safest and most efficient excavation sequence for PBA pilot tunnels.
The results are eye-opening. The group-tunnel effects are significant, with the degree of influence varying based on the excavation sequence. “The two-way four-pilot tunnel excavation has the most substantial impact, followed by the two-way double-pilot tunnel excavation, and then the two-way single-pilot tunnel excavation,” WANG explains. This hierarchy is crucial for understanding the stress levels on ingates, which are vital for maintaining structural integrity during construction.
For ingates, the maximum tensile stress occurs at the arch bottom, while the maximum shear stress is observed at the sidewalls and arch foot. The stress levels increase with the number of pilot tunnels excavated simultaneously. “The maximum shear stress of the ingate exhibits a leap-like increase with excavation progress and gradually stabilizes in the later stages of construction,” WANG notes. This insight is invaluable for engineers aiming to optimize construction sequences and ensure safety.
So, what does this mean for the future of metro station construction and the energy sector? The findings suggest that a two-way single-pilot tunnel construction sequence is more advantageous for improving the stress state of the ingates and ensuring safe breakthrough. This could lead to more efficient and safer construction practices, reducing costs and minimizing risks. For the energy sector, which often relies on underground infrastructure for power distribution and resource management, these insights could translate into more robust and reliable systems.
As cities continue to expand and the demand for efficient public transportation grows, the need for safe and efficient metro station construction becomes paramount. WANG’s research, published in ‘Urban Rail Transit Research’, provides a roadmap for navigating the complexities of underground excavation, paving the way for future developments in the field. The study underscores the importance of numerical simulations in understanding and mitigating the challenges of group-tunnel effects, offering a glimpse into the future of construction technology.