Methods and practices for deformation prediction in high-stress soft rock tunnels considering creep characteristics

To study the influences of high-stress soft rock creep characteristics on deformation prediction of surrounding rock of tunnels, the Muzhailing highway tunnel is taken as the support project. Firstly, the initial ground stress field is analyzed using a three-dimensional simulation model combined with multiple linear regression. The typical calculation sections are selected in conjunction with the section division of the surrounding rock. Secondly, the relevant method based on the BQ value is proposed to determine the parameters of the surrounding rock in the typical calculation section. Then, the section deformation is calculated based on the M-C model and the Cvsic model to analyze the influences of the creep characteristics of rock on the deformation of the surrounding rock. Finally, the predicted results are compared with the actual ones. The results show that: (1) The creep characteristics of rock mass have significant increase effects on the deformation, and the displacement growth rate is positively correlated with the average principal stress of cross-section. (2) The worse the surrounding rock condition, the more pronounced the creeping increase effects. The greater the average principal stress of the cross-section, the larger the displacement growth rate in the creep increase effects, while the change in the displacement growth rate is less noticeable. (3) The creep characteristics have significant effects on the prediction of the deformation level of the surrounding rock. The predicted results by the M-C model are weaker than those by the Cvisc model, which are pretty different from the actual deformations of the surrounding rock. The results lay a practical foundation for introducing the creep effects into the deformation prediction of high-stress soft rock tunnels.