地震作用下无衬砌黄土隧道围岩结构安全系数的计算探讨

Calculation discussion about safety factor of unlined loess tunnel wall rock structure under earthquake

为了得到无衬砌黄土隧道围岩结构在地震作用下的安全系数,借助有限元软件ANSYS,首先采用水平地震作用下的动力分析模型进行模态分析,得到质量阻尼系数和刚度阻尼系数;其次,输入地震波进行动力时程分析,得到模型顶点的最大水平位移;最后,采用静力分析模型,并考虑自重和左右边界上顶点水平位移最大时的侧向边界节点水平位移,通过不断折减围岩土体的抗剪强度参数,即黏聚力c和内摩擦角?,直到计算不收敛为止,从而得到无衬砌黄土隧道在地震作用下的安全系数。数值算例表明:所采用的方法是可行的,地震作用会使得围岩结构的安全系数降低,从而为以后黄土隧道围岩结构在地震作用下安全系数的计算及其工程应用提供了理论依据。

In order to obtain the safety factor of unlined loess tunnel wall rock structure under earthquake,general finite element software ANSYS is adopted.Firstly,modal analysis is done by adopting the dynamic analysis model under the horizontal seismic action;and the coefficient of quality damping and stiffness damping is obtained.Secondly,the dynamic time-history analysis is made by inputting seismic wave;and the maximum horizontal displacement of model ＂vertices＂ is gotten.Finally,by adopting static analysis model,and considering gravity and lateral border node horizontal displacement when the horizontal displacement of model ＂vertices＂ being largest on the border of right or left,and shear strength parameters,cohesion c and internal friction angle,of wall rock soil is continuously discounted until the calculation is not convergent so far;and so the safety factor of unlined loess tunnel wall rock structure under earthquake is obtained.Numerical example shows that the method proposed is feasible;and that earthquake action may make the safety factor of wall rock structure lower;and thus in the future a theoretical basis is provided for the safety factor calculation and engineering application of loess tunnel wall rock structure under earthquake.