Study on Deformation of Surrounding Rock for Deep-Buried Tunnels in Rock Mass of Interbedded Sandstone and Slate

Based on a constitutive model for rock mass of interbedded sandstone and slate, deformation of surrounding rock for deep buried tunnels in the rock mass was studied. The results show that the higher the slate content in rock mass is, the bigger the maximum displacement of surrounding rock is, and the more unsymmetrical the deformation of surrounding rock is. The variation of the internal friction angles of structural planes in slate has significant influence to the displacement of surrounding rock, which shows that one of the main failure features was the failure of structural planes in slate. The variation of the dip angle of rock mass is of great influence on the symmetry of deformation of surrounding rock. The distinct asymmetry of deformation of surrounding rock happens when the dip angle is in the range from 40^° to 60^°. The maximum displacement of the tunnel surrounding rock decreases with the increase of the dip angle when slate content is more than sandstone in rock mass. With the increase of the angle between the bedding strike and tunnel axis orientation, the deformation of surrounding rock decreases and tends to symmetry. In rock mass of interbedded sandstone and slate with steep dip angle, the angle between tunnel axis orientation and bedding strike should be designed as large as possible for the stability of surrounding rock. The results can provi.