Effects of lateral unloading on the mechanical and deformation performance of shield tunnel segment joints |
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| Affiliation: | 1. School of Civil Engineering, Central South University, Changsha, Hunan 410075, China;2. China Construction Fifth Engineering Division CROP., Ltd., Changsha 410004, China;1. Zhejiang University, College of Civil Engineering and Architecture, Hangzhou, Zhejiang 310058, China;2. CCCC Fourth Harbor Engineering Institute Co. Ltd, Guangdong, Guangzhou 510288, China;1. College of Civil Engineering and Architecture, Zhejiang University, 866 Yuhangtang Road, West Lake District, Hangzhou 310058, China;2. Research Center of Coastal and Urban Geotechnical Engineering, Zhejiang University, 866 Yuhangtang Road, Hangzhou 310058, China;3. Department of Geotechnical Engineering, Tongji University, Shanghai 200092, China;1. College of Civil Engineering, Tongji University, Shanghai, China;2. State Key Laboratory for Hazard Reduction in Civil Engineering, Tongji University, Shanghai, China;3. College of Civil Engineering, Ningbo University, Ningbo, China;1. State Key Laboratory for Hazard Reduction in Civil Engineering, Tongji University, Shanghai 200092, China;2. Department of Civil Engineering, Shanghai University, Shanghai 200072, China;3. College of Civil Engineering, Tongji University, Shanghai 200092, China;4. Department of Civil and Environmental Engineering, University of California, Davis, Davis, CA 95616, USA |
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| Abstract: | Unloading during lateral excavation widely occurs in existing subway shield tunnels. Previous studies have focused on the overall stress and deformation of existing tunnels caused by nearby unloading. However, the stress and deformation state of tunnel segment joints have yet to be considered. This study considered the non-continuity of the shield tunnel lining and the interactions among tunnel segment, surrounding rocks and ballast bed. A hybrid model of a shield tunnel was established based on 3D nonlinear contact theory. The mechanical and deformation properties of the segments and joints of an existing shield tunnel under the influence of lateral excavation of the foundation pits were studied. Unloading during lateral excavation caused the cross section of the shield tunnel to generate vertical convergence and shift horizontally towards the foundation pit. An opening and dislocation in the joint, which caused the waterproof ability of the joint to decrease sharply, were observed. Meanwhile, stress at the segment joint increased sharply and caused local cracks in the segment lining. Axial and shearing force on the joint bolt also increased significantly. Based on existing subway regulations, the calculation results were combined to establish a deformation control standard for existing shield tunnels under lateral excavation. The rate of vertical convergence of the lining should be less than 3.68‰, and the rate of horizontal shift of the axis should be less than 0.53‰. |
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| Keywords: | Shield tunnelling Segment joint Lateral unloading Deformation control standard 3D nonlinear contact model |
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