Objective Ground overload poses a safety risk to metro shield tunnels in operation. Single-hole double-track shield tunnels represent a future trend in metro tunnel development. Therefore, it is necessary to study the influence of ground overload on the mechanical performance of such tunnels.
Method Based on Shanghai Suburban Railway Airport Link Line, a finite element model is established to analyze and compare the overall mechanical performance of shield tunnels with different structural design forms under varying ground overload conditions.
Result & Conclusion Under various overload conditions, the maximum change in structural bending moments occurs at the top and bottom surfaces of the arched components, and that in shear force is observed at the top of the shield tunnel segments. The axial internal force in the middle partition wall transitions from axial tension to axial compression as the overload increases. The reinforcement amount in the shield tunnel segments increases with the rise of ground overload, and the reinforcement in arched components should be enhanced under excessive ground overload conditions. In contrast, the reinforcement in the middle partition wall shows little correlation with ground overload increase. In future design of similar engineering structures, attentions should be focused on whether the reinforcement in shield tunnel segments and arched components meets the maximum crack width requirements under specific overload conditions. The reinforcement in the middle partition wall is primarily governed by horizontal wind pressure loads generated by train operations, and no additional calculations are necessary under overload conditions on the ground.
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