强震区隧洞洞口段地震响应数值模拟研究

Numerical simulation of seismic response for tunnel portal section in strong earthquake area

假定地震波为垂直入射的弹性平面波,探讨隧洞洞口段平面波输入方法;基于拉、压条件下混凝土不同的损伤演化过程,建立适于编程的混凝土衬砌弹性动力损伤本构模型;针对地震作用下衬砌与围岩相互作用特点,建立衬砌与围岩联合承载分析模型;以处于强震区的滇中引水隧洞某出口段为实例,分析平面P波和SH波同时作用下洞口段的地震响应特性。研究结果表明:衬砌各部位位移与地震波的振动方向有关,峰值位移随着与洞口距离增大而减小,并在48 m处趋于稳定;在地震作用下,衬砌的损伤破坏以拉损为主,损伤系数随时间逐渐增大;衬砌中脱开区、滑移区的分布与其震损较严重区域的分布基本一致,主要分布于距洞口21 m之内的拱肩、拱腰和拱脚部位。

Assuming that seismic wave is vertical incident elastic plane wave,the plane wave input method for tunnel portal section was studied.Based on different damage evolution processes of concrete under tension and compression conditions,an elastic dynamic damaged constitutive model of concrete lining suitable for programming was constructed.According to the interaction characteristics between lining and rock under seismic load,an analytical model of joint loading between lining and rock was established.Taking an exit section of Dianzhong diversion tunnel in strong earthquake area as an example,the seismic response characteristics of portal section under synchronous actions of plane P wave and SH wave were analyzed.The results show that the displacements of different lining parts are related to the vibration direction of seismic wave,and the peak displacements decrease gradually from the portal to the interior,and then stay stable when the distance is 48 m.The damage failure of lining is mainly caused by tension under seismic load,and the damage coefficient increases gradually with time.The separation and slip zone distributions of the lining are basically consistent with its severe seismic damage area,which are mainly at spandrel,haunch and arch foot within 21 m of distance from the portal.