大断面盾构隧道管片接头抗弯力学模型研究

针对大断面盾构隧道复杂接缝面管片接头特点,考虑其接缝面细部构造、混凝土及传力衬垫的非线性力学特性、接缝面荷载传递特性以及接头螺栓预紧作用等因素的影响,建立了能够表征管片接缝面混凝土开裂与压碎、螺栓屈服以及接头破坏的管片接头抗弯力学模型,并结合管片接头抗弯足尺试验对大断面盾构隧道管片接头的抗弯性能进行对比分析。研究结果表明:弯矩较小时接缝面最大张开量增长较缓慢,当弯矩超过一定量值后,接缝面最大张开量显著增长;接缝张开高度超过螺栓位置而使螺栓受拉后,张开高度随弯矩增长幅度逐渐减小并趋于稳定值;负弯时接缝面的张开时机及螺栓的受力时机晚于正弯;轴力越大,接缝面的张开时机越晚,同等大小弯矩条件下张开高度的越小;管片接头抗弯刚度随弯矩增长总体呈非线性减小特点,轴力对于抗弯刚度的保持有益,轴力越大接缝面的抗弯能力越持久。研究结果可为大断面盾构隧道管片接头的设计提供指导与参考。

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.