STUDY ON THE BENDING MECHANICAL MODEL OF SEGMENTAL JOINT IN SHIELD TUNNEL WITH LARGE CROSS-SECTION

With the consideration of the influence of the detailed structure of joint surface, the non-linear mechanical property of concrete and transferring cushion, the load transmission distinction with joint surface and the impact of pre-tightened joint bolt, the bending mechanical model of segmental joint, which could characterize the crack and crush of concrete, the yield of bolt and the damage of segmental joint, is established for the segment joint with complex joint surface in large cross-section shield tunnel. Then the flexural behavior of segmental joint in shield tunnel with large cross-section is analyzed using full-scale test of segmental joint bending. The results show that the maximum opening of joint surface grows slowly under small moment, while it increases significantly when the bending moment exceeds a certain value. After the joint opening becomes wide enough and the bolt is in tension, the growth rate of joint opening height gradually decreases and approaches a stable value. The time of joint surface opening and the bolt becoming loaded under the action of negative curvature is later than positive bending state. Meanwhile, with the axial force increasing, the time of joint surface opening is later and the opening height is smaller than that under the same moment. The bending stiffness of segmental joint shows nonlinear descent with the moment growing, while the higher axial force is more favorable to maintaining the bending stiffness stability. A larger the axial force results in a longer flexural capacity of joint surface. The results can provide guidance and reference for segmental joint design for large cross-section shield tunnel.