Abstract：Research purposes: With the powerful development of the urban rail transit in China，the overlapped tracks of the urban rail transit are often laid out in some prosperous old downtowns in order to reduce the impact on city building ( structure) ． In this way，the small spacing and overlapped shield tunnel is formed． Taking the up and down overlapped tunnel in the section of the Hongling Station － Laozhanjie Station － Shaibu Station of the Line 3 of Shenzhen metro as the background，with the numerical simulation method，this paper discusses the impact of the train vibration on the structure and embedded soil of the shield overlapped tunnel，and discusses and analyzes the load bearing of the of the connecting bolt in order to take the corresponding technical measures in the design and construction．
Research conclusions: From the research on the shield overlapped tunnel with minimum clearance of 1． 6 m under effect of the train vibration load，it can be seen: ( 1 ) Under the effect of the dynamic load，the main stress of the soil embedded layer is mainly of the compression stress and it is in safety range under the effect of the train vibration load． ( 2) Under the effect of the dynamic load，the internal force of segment increases a little，but it is acceptable． ( 3) Under the effect of the dynamic load，the pulling force of the bolt on the completed block is the biggest among all hoop bolts of the segment of the upper tunnel，and it is necessary to reinforce the joint bolt because of the stress increase． ( 4) In order to ensure the safety of the railway traffic，the effective damping system should be installed for the up and down overlapped tunnel． This theoretical analysis can be as the theoretical analysis to the operation of the shield overlapped tunnel and as the reference to the similar works．
Gao Feng，Guo Jianyong． Research on Model Test of Doubie － decked Subway Tunnel under Train Vibration Loading［J］． Journai of the China Raiway Society， 2011( 12) : 93 － 100．
Zhang Liangtao． Test and Analysis of Vibration Induced by Elevated Railway and Antivibration Measure ［J］． Journal of Railway Engineering Society，2012( 6) : 118 － 125．
Lin Gang． Influence of Train Vibration on Structural Mechanical Behavior of Metro Overlapping Tunnel ［J］． Railway Construction Technology，2006( 3) : 9 － 11．
Tang Yiqun，Luan Changqing，Zhang Xi，etc． Numerical Simulation of Saturated Soft Clays Deformation Around Tunnel Under Subway Vibrational Loading ［J］． Chinese Journal of Underground Space and Engineering，2008( 1) : 105 － 107．
Bai Bing，Li Chunfeng． Three － dimensional Elastic Dynamic Response of Close Crisscross Tunnels Subjected to Subway Loading ［J］． Rock and Soil Mechanics，2007( S1) : 715 － 718．
2013, Vol. 30 
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