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Abstract Building piles，municipal pipelines，existing tunnels and other underground structures have hindered the construction space for the new tunnels because of dense city buildings and developed networks of existing subway tunnels. Then the new tunnels often inevitably overlapped cross and bypass cross the existing structures. Significant construction risks will be encountered during the complex above and down overlapped construction，and potential safety hazard will also be existed in service for the existing tunnels. Based on the tunneling case for Shanghai railway transportation line，the deformation prediction of subway tunnel in service induced by EPB shield in soft clay during above and down overlapped traversing process and its construction control are presented by using simplified theoretical method，3D finite element(FE) numerical simulation method，and in-situ monitoring method. The simplified theoretical method is originated from the Winkler foundation. The longitudinal settlement equation for existing tunnels due to above and down overlapped construction is obtained. The 3D numerical simulation method can optimize the construction scheme and shield excavation parameter. The practice case for above and down overlapped crossing with large oblique angle are analyzed. The in-situ monitoring method can obtain the measured data for subway tunnel in service induced by EPB shield and the setting rules of shield tunneling parameters，including earth pressure for cutting open，synchronized grouting，propulsion speed，segment assembling elevation，and cutter head torque. The proposed method may provide a theoretical basis for proposing correctly protective measurements of subway tunnels in service due to tunneling excavation during overlap traversing process. Furthermore，the research results can provide references to the future construction of other similar projects such as subway tunnels multi-line passing through existing structures.
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Received: 08 May 2012
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2013, Vol. 32 
