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Vibration Reduction Technology and Safety Control Standards for Multi-arch Tunnels without Middle Walls
(1. State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan 430071; 2. University of Chinese Academy of Sciences, Beijing 100049; 3. Panzhihua Qingjiabing Mining Co. Ltd.,Panzhihua 617200)
Abstract The existing lining and supporting structure of the first excavated tunnel in multi-arch tunnels without middle walls are prone to damage and failure due to blasting in the subsequent excavated tunnel. To address this issue, this study, based on the Mengxing—Lvchun Expressway Tunnel Project in Yunnan, analyzes the vibration response and damage distribution of the lining in the first excavated tunnel through field vibration monitoring and blasting damage simulation of the tunnel support structure. The vibration reduction effects of measures such as reserving isolation rock columns and laying foam concrete layers are evaluated. Reasonable thicknesses for isolation columns and the optimal positions of vibration reduction layers are determined, and a reliable safety control standard for blasting in multi-arch tunnels is proposed. The results show that: (1) Increasing the thickness of the isolation rock column in the excavation area can effectively reduce the lining vibration and damage. Considering subsequent secondary blasting for the reserved rock column, it is recommended to retain a 1 m wide rock column. (2) Placing the vibration reduction layer outside the initial support can significantly reduce the lining vibration. However, to minimize lining damage and enhance the overall tunnel stability, it is recommended to place the foam concrete vibration reduction layer outside the secondary lining of the first excavated tunnel. (3) The safety control standard for blasting in multi-arch tunnels is that the peak particle velocity (PPV) at the arch waist on the blasting side of the first excavated tunnel should not exceed 25 cm/s.
Abstract：
The existing lining and supporting structure of the first excavated tunnel in multi-arch tunnels without middle walls are prone to damage and failure due to blasting in the subsequent excavated tunnel. To address this issue, this study, based on the Mengxing—Lvchun Expressway Tunnel Project in Yunnan, analyzes the vibration response and damage distribution of the lining in the first excavated tunnel through field vibration monitoring and blasting damage simulation of the tunnel support structure. The vibration reduction effects of measures such as reserving isolation rock columns and laying foam concrete layers are evaluated. Reasonable thicknesses for isolation columns and the optimal positions of vibration reduction layers are determined, and a reliable safety control standard for blasting in multi-arch tunnels is proposed. The results show that: (1) Increasing the thickness of the isolation rock column in the excavation area can effectively reduce the lining vibration and damage. Considering subsequent secondary blasting for the reserved rock column, it is recommended to retain a 1 m wide rock column. (2) Placing the vibration reduction layer outside the initial support can significantly reduce the lining vibration. However, to minimize lining damage and enhance the overall tunnel stability, it is recommended to place the foam concrete vibration reduction layer outside the secondary lining of the first excavated tunnel. (3) The safety control standard for blasting in multi-arch tunnels is that the peak particle velocity (PPV) at the arch waist on the blasting side of the first excavated tunnel should not exceed 25 cm/s.
MENG Desheng1,
2 PENG Xiaodong3 YANG Guanghua3
.Vibration Reduction Technology and Safety Control Standards for Multi-arch Tunnels without Middle Walls[J] MODERN TUNNELLING TECHNOLOGY, 2024,V61(6): 251-260
2024, Vol. 61 