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Abstract Xi¢an metro under construction pass through many ground fissure active zones，the future large deformations of active ground fissure zones make a serious threat on Xi¢an metro tunnel. The genesis，moving mode and profile characteristics of active ground fissures in Xi¢an are analyzed，the active tendency and maximum vertical displacements of active ground fissures in the design life time of metro tunnel are estimated. The behaviors of metro tunnel passing through active ground fissure are studied with three-dimensional FEM，the results show that tunnel lining appears cracks when the vertical displacement of ground fissure increases to 20 cm，structural measures such as setting up seams in tunnel segmentation，adding flexible joints between segmented tunnel and enlarging tunnel lining cross-section should be adopted in structural design of metro tunnel passing through active ground fissure zones. Based on the deformation characteristics of active ground fissures and numerical simulation results，the three-dimensional moving model of metro tunnel which is perpendicular and oblique to active ground fissure zones，is respectively established，the reserved value of vertical，transverse and axial displacements for metro tunnel in design are calculated. The conclusions can be presented as the reference for lining structure design of tunnel passing through the ground fissure active zones.
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Received: 23 January 2009
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