The contribution of the bolting system to the shear stiffness of circumferential joints in tunnel segmental linings

The tunnel segmental lining is a type of support structure that is very complex and widely used in tunnel excavation. Of particular importance is the behaviour of circular joints in contact with adjacent rings. The shear behaviour of the circular joint is studied in detail in this paper. Particularly, bolts, which are widely used to connect the adjacent segments, play a fundamental role in the mechanical behaviour of the circular joints and therefore of the tunnel segmental lining. A new FEM model has been developed to be able to analyse the shear deformation of bolts, when two adjacent segments show a relative transversal displacement. The model allows to consider also the interaction of the bolt with the walls of the hole. It was possible to obtain the trend of the shear stiffness of the circular joint as the relative transversal displacements varied. A successfully comparison of the calculation results with the laboratory measurements was obtained. Some suggestions are proposed in order to enhancing the practicality of the model. The proposed numerical model is a useful calculation tool capable of correctly evaluating the mechanical behaviour of the circular joints and therefore to correctly represent them during the design stage.