Numerical Simulation on Creep Process of Surrounding Rock in Soft Rock Tunnel

Abstract

It is obvious that creep is one of important characteristics of surrounding rock in soft rock tunnel. There was less study on creep process of surrounding rock in the past which affected the engineer's judgment to long term stability of tunnel seriously. In this paper, the Cvsic model is selected and its parameters are determined based on soft rock creep test results, furthermore, the software FLAC3D was used to analyze the viscoelastic plastic creep process of surrounding rock in soft rock roadway. The results show that: the maximum creep rate occurs at the moment when the soft rock tunnel is excavated , then the creep rate decreases and finally evolves into steady creep; it will initially form a creep zone in the tunnel surface and then the deep surrounding rock will also form a damage zone by stress adjustment, forming a larger creep area; hoop stress decreases while the radial stress increases gradually from the surface to the deep rock mass of roadway, and eventually both will approach to the initial in-situ stress ; The plastic zone will gradually expand after the excavation of viscoelastic-plastic tunnel and tend to be stable when reaches to the steady creep stage. The hoop stress on the border between elastic and plastic zone of the surrounding rock reaches to peak stress; the deformation of surrounding rock changes suddenly and the deformation rate, the area of plastic zone increase with the increase of moisture content in the process of creep.