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Abstract Based on the study of repeatedly appearing geological hazards such as large deformation and collapse，and the formation mechanism and influencing factors of Dujiashan tunnel through soft rock which is under construction for Guangyuan—Gansu expressway，traversing the 5•12 fault zone in meizoseismal areas，it was shown that collapses were the main deformation failure of soft rock tunnels in meizoseismal areas；and most of them happened near the tunnel faces. The low strength of surrounding rock and softening effect from groundwater on rock mass are inducements of tunnel?s deformation，and there is also a vital factor that causes the phenomena above，i. e. the effect of the massive deep shattering damaged rock mass caused by 5•12 Wenchuan earthquake and the aftershocks. At the same time，the complicated regional environment caused by insufficient similar experience in design and construction is another key factor that cannot be ignored. The research indicates that，during the construction of soft rock tunnels in meizoseismal areas，proper adjustments of reserved deformation and safety control criterion should be taken based on practical engineering site，strong supporting parameters should be adopted，the techniques connecting each link during construction should be paid attentions to，and the disasters can be effectively controlled with the adoption of micro-bench method using three steps and reserved core soil excavation.
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Received: 20 November 2011
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2012, Vol. 31 
