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Abstract Based on the monitoring data of the Kuyu diversion tunnel，the deformation characteristics and mechanisms of the water-rich soft rock tunnel are analyzed. The results indicate that the convergence deformation of sidewalls and the subsidence of the vault develop towards constant values，the former takes much more days，and the value of the sidewalls deformation is 2–3 times as much as that of the vault. The deformation of soil tunnel is influenced by the combined tempo-spatial effects. And the ratio of deformation produced by the time-effect is quite large even in the range impacted by excavation. The effect distance of space-effect on sidewalls deformation is in range of 4D–5D. And comparing with the deformation of vault，the time-effect of the sidewalls deformation is more remarkable. The differences between the sidewalls and vault deformation characteristics are mainly determined by the types of rock deformation and the way of stress release. The time-effect of stress release of surrounding rock around the sidewall is obvious. The plastic area and deformation pressure increase with time and take a long time to reach stability. In a certain depth，the rock mass at the vault has an integral settlement deformation together；and the rock pressure can reach stability quickly. The research results can provide some scientific guidelines and valuable references for construction and monitoring of soft rock tunnel projects.
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Received: 20 May 2011
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2011, Vol. 30 
