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Analysis of Deformation Impact of the Adjacent Over-crossing Parallel Tunnel Excavated by the Shallow Mining Method on the Existing Shield Tunnels
(1. School of Civil Engineering, Inner Mongolia University of Science and Technology, Baotou 014010; 2. Academicians Workstation of Mine Safety and Underground Engineering, Inner Mongolia University of Science and Technology, Baotou 014010; 3. Technical Research Center for Urban Underground Engineering of Colleges and Universities in the Inner Mongolia Autonomous Region,Baotou 014010; 4. Beijing Urban Construction Design & Development Group Co., Limited, Beijing 100371)
Abstract Given that the tunnel excavated by the shallow mining method adjacently crossed over the existing Metro Line No.2 in a parallel way in Hohhot, the scheme comparison was carried out for different excavation methods and counter-pressure measures by means of finite element numerical simulation and on-site monitoring, and the study was conducted on the floating deformation pattern of shield tunnel structure caused by over-crossing construction.The results showed that the use of sandbags for counterpressure during construction could effectively control the deformation of shield tunnels, and through comparison, it has been found that the vertical displacement control rate of the second sandbag counterpressure was significantly lower than that of the first sandbag counterpressure. So, sandbag counterpressure for tunnels should be conducted during on-site construction as early as possible to avoid a smaller vertical displacement control rate caused by delayed counterpressure, which would further lead to a failure to realize a good effect of counterpressure. It has also been found that the curve of tunnel deformation of Metro Line No. 2 caused by the over-crossing works was of a "semi-parabolic" shape, and the phenomenon of left-right conversion occurred with the excavation and unloading of the new tunnel. Besides, unhomogeneous deformation occurred in shield tunnel segments due to various factors, such as soil unloading, shallow depth of overburden, etc. and the overall deformation of the existing shield tunnel segments was of a "vertical duck egg" shape. The finalized scheme of the Works was CD method + two-sided counterpressure based on economical factor, efficiency and other factors.After the optimization scheme was adopted in the Works, the maximum floating deformation of the shield tunnel roadbed was finally controlled at 2.51 mm, which complied with the specified control value, i.e. 4.0 mm.
Abstract：
Given that the tunnel excavated by the shallow mining method adjacently crossed over the existing Metro Line No.2 in a parallel way in Hohhot, the scheme comparison was carried out for different excavation methods and counter-pressure measures by means of finite element numerical simulation and on-site monitoring, and the study was conducted on the floating deformation pattern of shield tunnel structure caused by over-crossing construction.The results showed that the use of sandbags for counterpressure during construction could effectively control the deformation of shield tunnels, and through comparison, it has been found that the vertical displacement control rate of the second sandbag counterpressure was significantly lower than that of the first sandbag counterpressure. So, sandbag counterpressure for tunnels should be conducted during on-site construction as early as possible to avoid a smaller vertical displacement control rate caused by delayed counterpressure, which would further lead to a failure to realize a good effect of counterpressure. It has also been found that the curve of tunnel deformation of Metro Line No. 2 caused by the over-crossing works was of a "semi-parabolic" shape, and the phenomenon of left-right conversion occurred with the excavation and unloading of the new tunnel. Besides, unhomogeneous deformation occurred in shield tunnel segments due to various factors, such as soil unloading, shallow depth of overburden, etc. and the overall deformation of the existing shield tunnel segments was of a "vertical duck egg" shape. The finalized scheme of the Works was CD method + two-sided counterpressure based on economical factor, efficiency and other factors.After the optimization scheme was adopted in the Works, the maximum floating deformation of the shield tunnel roadbed was finally controlled at 2.51 mm, which complied with the specified control value, i.e. 4.0 mm.
XU Youjun1,
2,
3 QIN Haobin1 LI Wenbo4 ZHANG Xu1 etc
.Analysis of Deformation Impact of the Adjacent Over-crossing Parallel Tunnel Excavated by the Shallow Mining Method on the Existing Shield Tunnels[J] MODERN TUNNELLING TECHNOLOGY, 2022,V59(3): 118-127
2022, Vol. 59 