Contact surface flaw model for segment joints of segmented tunnel lining

To determine the normal spring stiffness with the Goodman element model for segment joints, the analysis results based on the classic elastic contact theory are compared to the experimental data firstly. As the assumption of smooth contact surface and elastic deformation of the classic theory can not explain perfectly the experimental results, the assumption of contact surface flaw is developed. From the point of view of this hypothesis, the joint element of the FEM model is utilized to trace the initial nonlinear displacement caused by the contact surface flaw at the initial loading phase. The normal spring stiffness of Goodman element is the secant stiffness of the curve of the axial force and the initial nonlinear displacement. Based on the assumption, the computational and verification methods for the spring stiffness are presented. The test calculations are performed, and the segment displacement and the bending moment-rotation relation are chosen as the verification criteria. The similar results of the FEM analysis and the full scale tests validate the applicability and suitability of the proposed method for the normal spring stiffness of joint elements.