Abstract
Rockburst, as a serious geological hazard, often poses significant threats to tunnel stability and construction safety. Traditional circular tunnels under non-hydrostatic pressure conditions tend to form localized stress concentration zones in the surrounding rock, which can easily induce rockburst. Elliptical tunnels with specific axis ratios have the potential to avoid this problem and have become one of the research hotspots in rockburst prevention. This paper analyzes the stress distribution and local concentration characteristics of tangential stress in conventional circular and elliptical tunnels. Based on this context, a theoretical method for rockburst prevention based on prestressed elliptical tunnels with optimal axis ratios is proposed, and a theoretical solution for the optimal axis ratio of prestressed elliptical tunnels is presented. Using a plateau tunnel as an engineering case study, numerical calculation results confirm that designing the shape of prestressed tunnels according to the optimal axis ratio can completely eliminate local tangential stress concentration, achieve a uniform distribution state, and significantly reduce the overall tangential stress level of the tunnel. Theoretically, it also has the advantage of achieving excavation stress compensation. This can provide theoretical reference for stress control and rockburst prevention in high ground stress tunnel engineering.
Full Text
Research on the Rockburst Prevention Theory and Method for Prestressed Elliptical Tunnels with Optimal Aspect Ratio
Zhang Boyi¹, Zhao Cheng¹²³*, Qian Yuan⁴, Sun Zeyuan¹, Xing Jinquan¹, Luo Yinfeng¹, Luo Qinyuan¹
¹Department of Geotechnical Engineering, Tongji University, Shanghai 200092, China
²Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education, Tongji University, Shanghai 200092, China
³School of Engineering, Tibet University, Lhasa, Tibet 850000, China
⁴Key Laboratory of Geotechnical Mechanics and Engineering of Ministry of Water Resources, Changjiang River Scientific Research Institute, Wuhan, Hubei 430010, China
*Corresponding author
Abstract
Rockburst is a severe geological hazard that poses significant threats to tunnel stability and construction safety. Under non-hydrostatic pressure conditions, traditional circular tunnels are prone to forming localized stress concentration zones in the surrounding rock mass, which can readily trigger rockbursts. Elliptical tunnels with specific aspect ratios offer the potential to mitigate this problem, making them a promising focus for rockburst prevention research. This paper analyzes the stress distribution characteristics and localized tangential stress concentrations in conventional circular and elliptical tunnels. Building upon this analysis, we propose a theoretical methodology for rockburst prevention utilizing prestressed elliptical tunnels with optimal aspect ratios, and derive a theoretical solution for determining this optimal ratio. Through a case study of a high-altitude tunnel project, numerical simulations confirm that designing the prestressed tunnel geometry according to the optimal aspect ratio can completely eliminate localized tangential stress concentrations, achieving a uniform stress distribution while substantially reducing the overall tangential stress level. The approach also offers the theoretical advantage of providing excavation stress compensation. This work provides a valuable theoretical reference for stress control and rockburst prevention in high-stress tunnel engineering.
Keywords: high-stress tunnels; rockburst prevention; tunnel cross-section shape; optimization design