Abstract：Taking the Wuhan Yangtze River tunnel as an engineering background，the 3D mechanical distribution characteristic of lining whose segment width ranges from 1 to 10 m is analyzed by establishing a 3D shell-nonlinear spring model which needs to input the nonlinear data about bending moment，axial force and rotating angle of segment joint. The analytical results about internal forces are contrasted with those calculated by traditional beam-nonlinear spring model. In addition，the internal force distribution rules of segment lining structure influenced by segment width are achieved. Finally，the rules are validated primarily by large-scale similar model test. The study shows that：(1) both the positive and the negative maximum bending moments of the 3D lining structure always occur on the edge of segment；(2) the maximum bending moment calculated by the beam-nonlinear spring model equals to that calculated by 3D shell-spring model on the edge of segment when it is assumed that the shear stiffness between rings is infinite，which indicates that using the results obtained by beam-nonlinear spring model to analyze lining structure is safe；(3) in the middle of the segment，the maximum bending moment calculated by the beam-nonlinear spring model is greater than that calculated by 3D shell-nonlinear model，so the reinforcement ratio of reinforced concrete in the middle of segment obtained by the beam-nonlinear spring model is greater than that by 3D shell-nonlinear spring model；and (4) the radial shear force on the ring joint calculated by the 3D shell-nonlinear spring model is less than that induced by the beam-nonlinear spring model，the larger the segment width is，the bigger the margin between them is. The study results can provide valuable references to reinforcement design of segment structure in the shield tunnel under the big river or sea and security appraisal of segment lining.
