Longitudinal Seismic Response of a Shield Tunnel Considering Longitudinal Bolt Prestress under Transverse Excitation

Abstract

A shield tunnel is an assembled structure that is composed of segments and connecting bolts, and its longitudinal seismic response needs to be investigated. Bolt prestress is a common measure for shield tunnels, and longitudinal bolts with different prestress can affect the longitudinal deformation stiffness of shield tunnels; therefore, they affect the longitudinal seismic response characteristics of the shield tunnel. Based on this, this paper establishes a longitudinal analysis model of a shield tunnel that considers longitudinal bolt prestress and uses an iterative algorithm to study the effect of longitudinal bolt prestress on the longitudinal force and opening of shield tunnels under transverse seismic excitation. Further, the detailed seismic response characteristics of the circumferential joint are studied. The results are as follows: (1) the internal force between the segmental rings under transverse excitation of the seismic load is dominated by the vertical bending moment; (2) under the bolt prestress, the bending moment between the rings and bending stiffness reduction coefficient are nonlinearly related. When the bending moment is less than the critical value, the bending stiffness reduction coefficient is assigned to one, which means that the circumferential joint interface does not open under the collective effect of the bolt prestress and bending moment; (3) the application of the bolt prestress increases the opening of the circumferential joints in the stiffness changed area, and decreases the opening in the position far from the stiffness changed area; and (4) the segment maximum principal stress and the largest stress of the bolt increase nonlinearly and monotonically with the increase in the prestress, which is not consistent with the changing law of the largest joint opening. The research results could provide some reference for the selection of the bolt prestress in a shield tunnel in an earthquake area.