轴力和弯矩共同作用下盾构隧道纵向非线性等效抗弯刚度研究

实际工程中,盾构隧道纵向弯矩和轴力可能同时存在,若按传统的纯弯等效抗弯刚度计算可能会带来较大误差。考虑轴力和弯矩共同作用对纵向弯曲变形的影响,提出5种弯曲模式,在经典的志波模型的基础上,建立盾构隧道纵向等效抗弯刚度计算模型,基于该模型开发了计算程序,以成都地铁3号线盾构隧道为实例,对其纵向等效抗弯刚度和管环张开量随轴力和弯矩的发展规律进行分析,并讨论弯曲模式的实用判别方法,求出变形过程的临界弯矩,最后给出纵向弯曲变形为线性和非线性的内力条件。研究发现:盾构隧道纵向变形随弯矩的发展过程可按轴力分为4类,各过程下管环张开量和等效抗弯刚度随弯矩的发展规律十分不同;轴力对等效抗弯刚度有显著影响,一般呈现压弯纯弯拉弯的规律。研究成果可应用于盾构隧道结构纵向力学分析、抗弯刚度分析等方面。

Nonlinear longitudinal equivalent bending stiffness of shield tunnel under the combined effect of axial force and bending moment

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.