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| Discussion on Design Method of General Safety Factor of Composite Lining Tunnel |
| XIAO Ming-qing |
| (China Railway Siyuan Survey and Design Group Co. Ltd, Wuhan, Hubei 430063, China) |
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Abstract Abstract：Research purposes： Composite lining is often used in the railway, highway and other traffic tunnels, and the primary support is generally designed by layer structure method or engineering analogy method, while the secondary lining is usually designed by load structure method, so it is difficult to evaluate the structural safety uniformly due to the difference of analysis methods. The current tunnel design code only specifies the safety factor requirements of secondary lining, but the composite lining is not a single structure, so it is necessary to study the general safety factor of primary support and secondary lining. And it is necessary to study the load-structure model of primary support to establish the design method of total safety coefficient. Research conclusions： (1) For composite lining structure with shotcrete and rock bolt support, the surrounding rock pressure increases with the increase of the buried depth, therefore the tunnel support parameters should be adjusted according to the buried depth. (2) The unified design method of composite lining including primary support and secondary lining can be established by the load-structure model. (3) The general safety factor of composite lining tunnel should include the safety contribution of both primary support and secondary lining. When using steel reinforced concrete as secondary lining, the general safety factor should be not less than 3.0, or else not less than 3.6. （4）Different distribution of safety factor on primary support and secondary lining suggested by different design methods is shown in table 2. (5) The result of reanalysis on the structural safety of existing high-speed railway tunnel using this design method shows that when the buried depth is about 300 m, the supporting parameters of tunnel in surrounding rock of Ⅲand Ⅳ grade can be further optimized. (6) The research results can provide ideas and methods for structural design of composite lining tunnel.
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Received: 15 November 2017
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2018, Vol. 35 
