Experimental study on behaviors of segment linings in an anisotropically jointed rock mass

As the structural strength in the deep layered rock is of anisotropic characteristics, the segment lining is susceptible to unsymmetrical pressure when the shield tunnel is constructed in such formations. Similar model tests are carried out to study the interaction between layered surrounding rock and shield segment lining, and the pressures on the surrounding rock behind the segment lining, internal forces and deformations of the segment lining are investigated. The research results indicate that the stress and deformation characteristics of the segment lining are obviously controlled by bedding plane, the segment lining is pressed very unevenly, and the axial forces, bending moments and deformations exhibit asymmetrical distribution. The maximum pressures on the surrounding rock behind the segment lining are concentrated in the normal direction of the weakest plane, and in this direction, the bending moments of the segment lining are the largest, the axial forces are the smallest and the deformations are the largest. The bedding angle has significant influence on the stress and deformation of the segment lining as well as the distribution and size of pressures on the surrounding rock. In the homogeneous surrounding rock, the fractures of the segment lining are mainly located at the joints of the key segment and other annular joints, while in the layered surrounding rock, the location of fractures of the segment lining is weakened by the influence of the position of joints, and the influence of the bedding dip is obvious. The location of fractures of the segment lining is mainly concentrated in the normal direction of the weakest plane. The results of this study have certain reference value for the design of the supporting structure type of shield tunnels in layered surrounding rock.