Abstract：In practice，the bending moment and axial forces in the longitudinal direction of shield tunnel may exist simultaneously. The traditional method evaluating the equivalent bending stiffness under the conditions of pure bending may bring errors. In this paper，5 kinds of bending modes have been proposed to consider the combined effect of axial force and bending moment on longitudinal bending deformation. Furthermore，a model calculating the longitudinal equivalent bending stiffness of shield tunnel was established based on the classical SHIBA model. A computer program was written for the implementation of the model. The shield tunnel of Metro Line 3 in Chengdu as was analyzed. The practical method of determining the bending modes was discussed, the critical bending moment in deformation process，and the internal force condition of linear or nonlinear bending deformation were given. The results show that the process of longitudinal deformation of shield tunnel with bending moment can be divided into four categories according to the axial forces. The development of the equivalent bending stiffness and the opening of segment ring are very different. The axial forces has a significant effect on the equivalent bending stiffness，generally，the compression bending >> pure bending＞stretch bending.
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[3]
叶耀东. 软土地区运营地铁盾构隧道结构变形及健康诊断方法研究[博士学位论文][D]. 上海：同济大学，2007.(YE Yaodong. Research on deformation and method of health diagnose of operational subway structures in soft soil[Ph. D. Thesis][D]. Shanghai：Tongji University，2007.(in Chinese))
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2017, Vol. 36 
