Abstract：Segments are the basic structure units in shield tunnel. The loads and relative mechanical behaviors of segments are different between construction stage and regular service stage. The cracks usually appear in construction stage，which hit the research on mechanical behavior of segments in construction stage more important. Three-dimensional finite element method is used to analyze a tunnel with 9 segment rings. The loads include injected pressure，jacking force and squeezing action of tail of shield machine. The analytical results indicate that，during construction stage，the difference of loads along longitudinal direction causes various displacements and stress distributions in different segment rings；and the displacements of different rings show discrepant. The constitutions of wedge-shaped segments make the out-of-plane displacement happen in segment rings even in uniformly injected pressure. The out-of-plane displacement causes the dislocation of segments. When the injected pressure is nonuniform，the dislocation will be enlarged，and it will finally cause cracks in segments. The jacking force has apparent effects on displacement and stress distribution of segments，and it is the most adverse load case during construction stage.
