Feasibility study on local full-scale experiment's boundary of longitudinal joint of shield tunnel

Along the longitudinal direction of the shield tunnel, the joint between the two segment rings is called the longitudinal joint. The longitudinal joint is the weak part of the deformation restrained by the adjacent segments during the deformation process, and its mechanical characteristics are different from those of the segment joint. In this work, the feasibility of local test of longitudinal joints was studied by numerical simulation. Then, the full-scale tests on longitudinal joints were carried out to study the deformation characteristics of the joints. The conclusions are summarized as follows: when analyzing longitudinal joints and comparing the results calculated by the whole ring model and the longitudinal equivalent stiffness beam model, the differences in the results of joint opening amount and bolt stress are within 11%, and the distribution characteristics of the plastic damage zone of the segment structure are basically the same, so that the longitudinal equivalent stiffness beam model can be used for local full-scale test of the longitudinal joint. According to the local full-scale test, the change of the opening amount of the longitudinal joint is more sensitive to the axial force, and the bolt strain growth is basically consistent with the increase of the ring force (axial force, bending moment).The seam angle is close to 0 under the circumferential tension and follows the change of the circumferential bending moment. In each working condition, the maximum tensile strain of the surface layer concrete of the component appears on the middle of the outer surface of the sleeve side segment, and the maximum compressive strain occurs on the inner surface of segments at the hand hole side. In the failure test, when the longitudinal tensile force is 323.2 kN, the segment structure fails before the bolt, and the bolt does not reach its yield strength. © 2020, Editorial Office of China Civil Engineering Journal. All right reserved.