Static and dynamic characteristic analysis of segment joints based on three-dimensional discontinuous contact model

Based on the nonlinear contact theory and considering the discontinuity of shield tunnel structure, a three- dimensional discontinuous contact model for track bed-segment-surrounding rocks is established by simulating the segment joints and the interaction between the segment and the surrounding rocks as well as the track bed. The mechanical and deformation properties of the segment joints under the pressure of the surrounding rocks and the action of the subway train dynamic load are analyzed in depth based on this model. The results of numerical simulations show that under the pressure of the surrounding rocks, some longitudinal joints in arch crown area and arch bottom open inwards; some joints in haunch of shield tunnel open outwards; and the dislocations between the completed blocks and the adjacent blocks in arch crown area are comparatively large. The joints in haunch are compressed obviously and those in arch crown have the minimum pressure under the pressure of the surrounding rocks. The axial forces of joint bolts in vault area are relatively the greatest, those in arch bottom come second, and those in haunch are the smallest. The shearing forces of joint bolts in the top of arch foots are also the greatest when segment ring rotates to an angle so as to complete assembly. The opens and dislocations of the segment joints, concrete stress and internal forces of joint bolts all increase rapidly at the beginning of the dynamic load, then significantly decrease, and finally are fluctuant under the action of dynamic load of subway trains. The dynamic response of joints in arch crown is more obvious than that in arch bottom for shallow buried metro tunnels. The shearing forces of joint bolts increase more than the axial forces under the action of dynamic load of subway trains.