Full-scale experimental and structural characterization study of shield tunnel reinforcement under ground stacking loads

To investigate the internal force response characteristics and reinforcement effects of the shield tunnel segment structure in the presence of ground load disturbances in the Hangzhou Metro, full-scale tests were conducted on three-ring misaligned assembled segments using a self-developed "Shield Tunnel Segment Hydraulic Loading System." The study examined the structural characteristics of tunnel segments under the influence of different ground resistance coefficients (lambda) and eccentric loads (P), and explored the reinforcement effects of the internal tension ring method from multiple perspectives. The research results indicate that under different ground resistance coefficients (lambda), the sensitivity of internal force response is concentrated in the waist concrete, with a maximum bending moment reduction of 88.8%. The effective rate of bending stiffness tends to flatten, joint bending moment transfer effects strengthen, and the bearing capacity of the segments significantly increases after reinforcement, leading to a more uniform overall structural response. Under different eccentric loads (P), the bending moment of the segments after reinforcement approximates central symmetry with a reduced distribution range. The rate of change of the effective bending stiffness (eta) shifts from "rapid" to "slow," and the variation of joint bending moment transfer coefficient (zeta) stabilizes. The reinforcement with steel rings significantly enhances the overall stiffness of the segments and reinforces the joint bending moment transfer effect. The reinforcement effect of the segments can be evaluated through the bending moment transfer coefficient and effective bending stiffness. After reinforcement, the bearing capacity of the segments is noticeably enhanced, and significant forces are observed at two locations in the right waist joint, where the combination of steel plates and segments exhibits optimal performance.