隧道在黏弹性边界下地震动输入方式比较研究

Comparative Study on Ground Motion Input Methods for Tunnels under Viscoelastic Boundary

目前对于隧道地震响应分析,大多采用黏弹性人工边界作为动力边界,而对于地震动输入方法并无详细对比。采用ABAQUS有限元分析软件,建立隧道-土层三维模型,验证了黏弹性人工边界的准确性和地震动在不同分界面处的反射透射现象。在此基础上,以青岛某公路隧道为例,分别使用位移输入、加速度输入和等效节点力输入施加地震荷载,研究隧道在不同输入方式下的动力响应特征。结果表明:输入方式对隧道地震响应结果有重要影响;位移输入和加速度输入结果等效,其隧道位移响应最小为节点力输入的0.12倍,应力响应最大达到节点力输入的2.45倍,计算结果偏大;等效节点力输入的隧道位移响应结果符合解析解,应力分布符合实际规律。在进行隧道地震响应分析时,应优先考虑使用等效节点力方式输入地震动。

At present,the viscoelastic artificial boundary is used as the dynamic boundary for seismic response analysis of tunnels,but there is no detail comparison on the seismic input method.Using ABAQUS finite element analysis software,a three-dimensional model of tunnel-soil layer is established to verify the accuracy of viscoelastic artificial boundary and the reflection and transmission of ground motion at different interfaces.Taking a railway tunnel in Qingdao as an example,the displacement input method,the acceleration input method and the equivalent nodal force input method are respectively used to study the dynamic response characteristics of the tunnel under different input methods.The results illustrate that the input method has a significant effect on the seismic response of the tunnel.The results of displacement input and acceleration input are equivalent.The minimum displacement response of the tunnel is 0.12 times that of the node force input,and the maximum stress response is 2.45 times that of the node force input.The results of tunnel response displacement with the nodal force input method are more consistent with the analytical solution and the calculation accuracy is much higher.Therefore,the equivalent node force input should be given priority in the seismic response analysis of tunnels.