Evaluation of structural analysis of tunnel segmental lining using beam-spring method and force-method (Case study: Chamshir water conveyance tunnel)

The joints between segmental rings can withstand a certain amount of bending moment as well as axial and shear forces. Generally, in the structural analysis of tunnel segmental lining, the joints can be modeled as elastic hinges or rotational springs, and their rigidity should be demonstrated in terms of the rigidity of the joints or their rotational stiffness. Therefore, the bending moment acting on the tunnel lining is reduced. Hence, the tunnel designers are free to choose a lining with a lower cost. In this research work, especially considering the joints, the structural analysis of the segmental lining with variation in the flexural stiffness of the joints ( ), soil resistance coefficient ( ), number of segmental lining joints, and joint arrangement of segmental lining were carried out by the Force-Method equations. The imposed bending moment and axial forces were computed based on the Beam-Spring method, which is widely used to analyze the internal forces of segmental lining, and compared them with the results of the Force-Method equations. Then the effects of joint arrangement patterns and joint rotational spring stiffness on the results of the Beam-Spring analysis were evaluated. Finally, the optimum characteristics of the reinforced concrete segmental lining design were evaluated using the interaction diagram of bending moments and axial forces. The results obtained showed that the presented pattern for the segmental lining at the Chamshir tunnel was imposed against the external pressures on the segmental lining with an acceptable safety factor.