Investigation of response of metro tunnels due to adjacent large excavation and protective measures in soft soils |
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| Affiliation: | 1. Department of Civil Engineering, Zhejiang University, Hangzhou 310058, China;2. College of Civil Engineering, Hunan University, Changsha 410082, China;3. Ningbo Rail Transit Project Construction Headquarter, Ningbo 315012, China;1. College of Civil Engineering and Architecture, Zhejiang University, 866 Yuhangtang Road, Hangzhou 310058, China;2. Research Center of Coastal and Urban Geotechnical Engineering, Zhejiang University, 866 Yuhangtang Road, Hangzhou 310058, China;3. School of Civil Engineering and Architecture, Zhejiang Sci-Tech University, Hangzhou 310018, China;1. School of Environment and Architecture, University of Shanghai for Science and Technology, 516 Jungong Road, Shanghai 200093, China;2. Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education, Tongji University, Shanghai 200092, China;3. State Key Laboratory for Geomechanics and Deep Underground Engineering, China University of Mining and Technology, Xuzhou 221116, China;4. Department of Geotechnical Engineering, Tongji University, Shanghai 200092, China;1. Department of Civil and Environmental Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong;2. Key Laboratory of Geomechanics and Embankment Engineering of the Ministry of Education, Geotechnical Research Institute, Hohai University, 1 Xikang Road, Nanjing 210098, China;1. State Key Laboratory of Ocean Engineering, Department of Civil Engineering, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai, China;2. Shanghai Urban Construction Design and Research Institute, 3447 Dongfang Road, Shanghai, China;3. Shanghai Foundation Engineering Co. Ltd., 406 Jiangxi Middle Rd., Shanghai 200002, China;1. Key Laboratory of Ministry of Education for Geomechanics and Embankment Engineering, Hohai University, Nanjing 210098, China;2. Jiangsu Research Center for Geotechnical Engineering Technology, Hohai University, Nanjing 210098, China;3. Department of Civil and Environmental Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong;1. State Key Laboratory of Ocean Engineering, Department of Civil Engineering, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai, China;2. Shanghai Tunnel Engineering Co., Ltd., 118 Dalian Rd., Shanghai 200082, China |
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| Abstract: | The inevitable influence of large excavation in soft soils on nearby tunnels is of great concern in practice. In this paper, the influence of a nearby large excavation on existing metro tunnels of the Ningbo Metro Line 1 in sensitive soft soils is investigated and presented. Considerable displacement in the left tunnel closer to the excavation induced by the nearby excavation was revealed by field monitoring. Visible cracks and leakages were observed in left tunnel linings. Three dimensional numerical simulations are conducted to investigate the responses of the ground and left tunnel due to the adjacent excavation. The development of bending moment and displacement of the left tunnel during different construction stages of the nearby excavation is obtained. Then the interaction mechanism between the nearby excavation, surrounding soils and existing twin tunnels is investigated, which is of significance to the interpretation of the influence of the nearby excavation on the existing twin tunnels. Several protective measures for alleviating the influence of adjacent excavation on left tunnel are studied, including divided excavation, soil improvement and a cut-off wall. It is found that the left tunnel is influenced to varying degrees during different construction stages and the time effect is distinct for this large excavation in soft soils, which would be suggestive to engineers to pay more attention to the protection of adjacent tunnel during the crucial construction stages. The bending moment and displacement of the left tunnel is strongly related to the unloading effects and displacement of surrounding soils, which can be alleviated by means of proper improvement of excavation sequence. Comparatively, longitudinally divided excavation is more effective in protecting the left tunnel than soil improvement or a cut-off wall. This study is of certain reference value for protecting metro tunnels adjacent excavation in soft soils. |
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| Keywords: | Numerical analysis Tunnel Excavation Displacement Bending moment |
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