Abstract: The deformation of surrounding rock around a deep tunnel is a complex nonlinear mechanical problem. The creep in whole process and dilatation of the rock are two significant factors. Based on the Hoek-Brown criterion, the nonlinear stress solutions are obtained with and without the condition of the surface force around the tunnel, and dilatancy angle is introduced to consider the influence of the plastic volume change. Then an expression of viscoelastoplastic creep displacement is deduced under the nonlinear stress state using Hohai model which can describe the whole process of creep. Finally, the influence of the surface force around tunnel and dilatancy angle on the creep displacement of tunnel wall is discussed with different NVPB creep parameters and different material parameters m. The results show that under high ground stress the whole creep curve can be obtained by describing the creep problem of deep tunnel surrounding rock with the nonlinear creep model. In addition, the creep displacement of tunnel wall increases with the decrease of the surface force around tunnel and the value m, or the increase of the dilatancy angle, which is unfavorable to the long-term stability of surrounding rock. The results can be used to forecast the surrounding rock collapse of deep tunnels.

Key words: deep tunnels, surrounding rock, whole process of creep, dilatation, Hoek-Brown yield criterion, nonlinear creep model