To rationally and economically select a feasible lining structure for the shield section of the Jintang subsea tunnel of the Ningbo-Zhoushan railway,the characteristics of the subsea shield tunnel such as ultrahigh water pressure,ultralong distance,complex sea environment,and challenges in disaster prevention,evacuation,and rescue are summarized.A comprehensive comparison of single-and double-layer lining structures is conducted in terms of structural stress and deformation,specific subsea working conditions,longitudinal seismic response,and risk mitigation.This analysis establishes the necessity,feasibility,and economic advantages of the double-layer lining structure.In addition,the double-layer lining structure section is optimized to enhance the effective clearance area and subrail structure type,enabling the realization of a full-ring superimposed double-layer lining.The findings reveal the following:(1)Under static load conditions,the structural deformation of the double-layer lining scheme is relatively small,benefiting track smoothness,though comparable to the single-layer lining scheme.Space should be reserved for secondary lining,considering the complex construction environment of the sea section and long-term safety.(2)Under longitudinal earthquake conditions,the composite lining structure,consisting of the secondary lining and segment,demonstrates stronger connection performance,jointly bearing the load.This significantly reduces the peak deformation and stress of the segment,with a maximum decrease of 20.58%at the crown.Shock absorption measures address the vulnerability of the secondary lining to tensile damage.(3)Using the R=P×C grading risk assessment method,the risk reduction cost(RMB 342 million)is lower than the expected risk loss cost(RMB 347 million),indicating the superiority of the double-layer lining structure.(4)The effective above-rail net clearance area is optimized to 83.79 m2,resulting in a reasonable change in the maximum stress on the train surface and transient pressure.The net clearance area is 4.3%less than the double-layer lining with a net clearance area of no less than 90 m2 and a cross-sectional diameter of 14.6 m.(5)Based on disaster prevention,evacuation,and rescue requirements,as well as the aerodynamic effects of the cross-section,the subrail structure type is optimized.The circle range of the full-ring superimposed double-layer lining achieves 90.70%,with the cross-section diameter reduced by 2.1%compared to the full-ring 30 m cast-in-place secondary lining,which has a cross-section diameter of 14.3 m.
万方数据
维普
