隧道围岩结构地震动稳定性分析的动力有限元强度折减法

为了得到隧道围岩结构的地震动安全系数,借助通用有限元软件ANSYS,首先对水平地震作用下的模型进行模态分析,得到质量阻尼系数和刚度阻尼系数;其次由静力分析模型得到竖向边界上的水平向支座反力,然后将结构自重转化为温度边界条件,通过热分析得到模型各节点的温度,从而实现在动力分析中考虑重力的影响;最后采用悬臂梁动力分析模型,导入热分析获得的模型各节点的温度,并在竖向边界上施加水平向支座反力,通过不断折减围岩塑性区的凝聚力c和内摩擦角Φ,直到计算不收敛为止,从而得到隧道围岩结构的地震动安全系数。数值算例结果表明:采用的方法是可行的,将围岩结构自重转化为节点温度的措施解决了以往动力分析不能考虑结构自重的难点,进而为以后地震作用下隧道动力安全系数的计算及其工程应用提供了理论依据。

Dynamic finite element strength reduction method of earthquake stability analysis of surrounding rock of tunnel

In order to obtain earthquake safety factor of surrounding rock of tunnel, using FEM software ANSYS, firstly, modal analysis is done by adopting the model under the horizontal earthquake action; and then mass damping coefficient and stiffness damping coefficient are obtained. Secondly, the horizontal support reaction force along the vertical borders is obtained by the static analysis. Thirdly, for considering the gravity influence in dynamic analysis, structure gravity is become into temperature boundary condition; and the temperature of each node in model is obtained by thermal analysis. Finally, adopting the dynamic analysis model of cantilever beam, and inputting into the node temperature which is obtained by using thermal analysis, and applying the level support reaction force along the vertical borders, cohesion c and friction angle ? in plastic zone are continuously discounted until the calculation is not convergent; and then the earthquake safety factor of surrounding rock of tunnel is obtained. Numerical example result shows that this approach is feasible, the measure that the structure gravity is become into the node temperature solves the difficulty that the structure gravity can not be considered in previous dynamic analysis; and so a theoretical basis is provided for dynamic safety factor calculation and engineering application of surrounding rock of tunnel under earthquake.