Study On Seismic Performance Of Double-layer Lining Of Shield Tunnel

With the increasing modernization of China's transportation system,the shield tunnel is gradually developing towards the direction of large cross-section,largely buried depth and super-long.Because the single-layer segment lining structure has been unable to meet the expected design purpose and structural durability requirements,the double-layer lining structure has been gradually adopted.Seismic is very frequent in China for a long time.How to correctly understand the ground motion response characteristics of double-layer lining structure is a significant problem now.Based on the Shiziyang tunnel project of Guangzhou-Shenzhen-Hong Kong Dedicated Railway,this paper carries out systematic researches on the ground motion response law of shield tunnel double-layer lining structure by using the research method of data investigation and numerical analysis.Here are research results obtained:(1)Contact pair is used to simulate inter-layer mechanical transfer,and based on the three-dimensional solid numerical calculation model of double layer lining,the seismic response characteristics of composite and superimposed double layer lining structures are studied in this paper.With the increase of elevation,the acceleration amplification effect of the structure increases gradually inhomogeneous strata.Because of the large deformation of the composite secondary lining,the acceleration fluctuates greatly at different positions.The cross-section deformation of double layer lining is mainly oblique 45 °elliptical deformation,and the stress concentration is relatively concentrated in the conjugated 45 °region of the structure.The distribution law of maximum principal stress in the longitudinal bolt of segment joint shows a phenomenon of large in middle and small on both sides,and the maximum principal stress of the bolt at the arch shoulder and the arch foot is obviously greater than that at other positions.The time of opening peak value of segment annulus is different at different positions,and the opening amount of annulus at the position of the arch shoulder and arch foot is obviously larger than that of other locations.(2)With the increase of peak acceleration of seismic wave,the internal force of double layer lining increases approximately linearly,the ratio of axial force of segment to secondary lining decreases approximately logarithmic,and the stress of longitudinal bolt and the opening of the annular joint of segment gradually increase.The reduction of segment strength makes the bending moment decrease obviously,and the axial force of the secondary lining increases obviously in the left arch foot where the axial force is larger.With the degradation of segment strength,the stress of longitudinal bolt and the opening of the annular seam of segment increase gradually.(3)With the increase of buried depth of the tunnel,the stress of longitudinal bolt,the amount of annular joint opening of the segment,the internal force and stress of segment and secondary lining increase at first and then decrease.When the buried depth of the tunnel increases gradually,the stress and deformation of the structure increase gradually,and the structure is in a disadvantageous state.When the tunnel enters the deep buried state,the stress and deformation of the structure decrease slowly and the structure is in a safer state.