Segmental tunnel lining is a tunnel lining that is adopted when the Tunnel Boring Machine (TBM) is used as excavation machine. It is a concrete lining that is assembled with segments, connected to each other through various devices, including connecting bolts. In order to correctly analyze the behavior of the segmental lining in the longitudinal direction of the tunnel, when actions and loads stress and deform it, it is necessary to know an important mechanical parameter: the shear stiffness of the circular joint. In turn, this fundamental mechanical parameter depends on the behavior of the connecting bolts inside their housing hole. In this work, the behavior of the connecting bolts inside the housing holes was analyzed in detail, through three-dimensional numerical modeling, considering the characteristics of the interaction between the bolt itself and the hole wall, when a relative movement of the lining rings at the circular joint deform the bolt. Thanks to back analysis procedures of experimental laboratory measurements, it was possible to determine the values of some interaction parameters on the bolt-sleeve/concrete interfaces, which are necessary for a correct three-dimensional numerical modeling. The developed numerical model was able to fully describe the behavior of the connecting bolts inside their housing holes and, therefore, also of the circular joint when it is subjected to shear forces that produce the dislocation of the lining rings. The calculation results were compared with experimental measurements obtained from a real-scale tests giving positive results. Thanks to the carried out studies and the developed calculation tool, it is now possible to identify the shear stiffness values of the circular joint with a great detail, in order to evaluate then the mechanical behavior of the segmental lining when subjected to actions and loads (like buoyancy forces due to a liquid filling material around the lining) acting in the longitudinal section of the tunnel. •Tunnel segmental lining is assembled in segments, connected to each other through various devices, including connecting bolts. The shear stiffness of the circular joint is a fundamental parameter to be able to understand the lining stress-strain condition; it depends on the behavior of the connecting bolts inside their housing hole.•The behavior of the connecting bolts inside the housing holes is analyzed in detail, through three-dimensional numerical modeling, considering the characteristics of the interaction between the bolt itself and the hole wall, when a relative movement of the lining rings at the circular joint deform the bolt.•Thanks to back analysis procedures of experimental laboratory measurements, it was possible to determine the values of some interaction parameters on the bolt-sleeve/concrete interfaces, which are necessary for a correct three-dimensional numerical modeling.•The developed numerical model is able to fully describe the behavior of the connecting bolts inside their housing holes and, therefore, also of the circular joint when it is subjected to shear forces that produce the dislocation of the lining rings.•Thanks to the carried out studies and the developed calculation tool, it is now possible to identify the shear stiffness values of the circular joint with a great detail, in order to evaluate then the mechanical behavior of the segmental lining when subjected to actions and loads acting in the longitudinal direction of the tunnel.