| It has been shown from a lot of shield tunnels in operation that excessive transverse deformation of tunnel structure caused by the impacts of exterior action is increasingly common. Its detrimental influence on tunnels includes large deformation in diameter direction, large opening of the longitudinal joints, segment breakage, water leakage and segment cracks, etc., which endangers the operational and structural safety of the tunnel. The transverse deformation is determined by transverse rigidity of the tunnel, which is counted by the value of transverse effective rigidity ratio to show the reduction of transverse stiffness of the homogeneous ring in modified routine method. A direct relation is found among transverse deformation, transverse rigidity and the value of effective rigidity ratio. However, in large deformation stage of the tunnel the value in the simplified structural calculation model is lack of accuracy and reasonability on account of existing studies mostly confining to elastic stage of deformation. Based on the background, the development pattern of transverse deformation and the exact value of transverse effective rigidity ratio of shield tunnel have been deeply studied with three-dimension refined numerical simulation in present paper. The research results could not only provide valuable reference for the maintenance of shield tunnel during operation period, but also improve the calculation and analysis theories of shield tunnel. The achievements are concluded as follows:(1) On the basis of segmental lining structure of typical metro shield tunnel in Guangzhou, three types of two-ring(1/2+1+1/2) three-dimensional refined numerical models consisting of transverse uniform pattern(the homogeneous rings without considering any circular joints but longitudinal joints), straight-jointed installation pattern and stagger-jointed installation pattern are established. Then, the vertical line load in the vault of tunnel is applied on each model to study the characteristics and variation law of straight-jointed and stagger-jointed structural transverse deformation respectively, by analyzing the following four aspects: diameter and radial deformation of segmental ring, the opening of longitudinal joints and concrete cracks.(2) A new calculation method of transverse effective rigidity ratio has been proposed on the basis of discussion of existing researches. Then, based on above numerical simulation the exact value and variation law of straight-jointed and stagger-jointed structural transverse effective rigidity ratio are studied respectively.(3) Combined with the characters of structural design and construction of shield tunnel, three parameters including bolt pre-tightening force, bolt strength grade and reinforcement strength grade are taken into consideration in the impact analysis about transverse deformation and value of transverse effective rigidity ratio of straight-jointed and stagger-jointed shield tunnels. |
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