The role of the planar joints without bolts on the structural behaviour of coupled segmental tunnels built in soft soils

Abstract

This paper aims to evaluate the role of planar joints without bolts on the structural behaviour of segmental tunnels. Segmental tunnels could be vulnerable to deformation problems due to the presence of the joints, such as segment cracking, joint damage and its opening. As a result, the lining presents a limitation of its load capacity and stiffness loss that can jeopardize its safety and durability. Thus, in this paper the joint influence was evaluated on the lining behaviour with different structural parameters. These parameters were relative height of joints, slenderness ratio and pressure ratio of the lining. The lining behaviour was estimated by numerical models that included the nonlinearity of joints and materials using a 3D finite element model. The joint influence was studied through the stiffness, the load capacity and the failure mechanism of the lining. It is concluded that the joints have a main influence on the structural behaviour of the lining. For example, in the bending domain due to the joint opening and the damage by the coupling effects, as the diametral deformation of the lining increases, the stiffness decrements. This stiffness loss reached without the reinforcement yields. On the other hand, in the compression domain, the stiffness loss begins with the joint failure by concrete bursting. The joint losses its capacity to transfer load. It develops a failure mechanism of lining at lower deformation. Thus, the design lining should be based on a suitable role of their joints.