近断层/远场地震动作用下隧道结构易损性研究

以川藏铁路线控制性工程——折多山隧道为研究对象,建立隧道动力时程分析模型。结合场地地震动设计反应谱,选取近断层脉冲型地震动及远场地震动记录,用于增量动力分析隧道工程结构的抗震性能水平。初步探讨适用于隧道结构的地震动强度指标IM,分析不同特征部位隧道结构易损性,对比分析近断层脉冲型地震动及远场地震动作用下隧道结构的地震易损性概率,并进一步给出在2种不同地震动作用下隧道结构在三级设防要求下的失效概率。结果表明:对于隧道结构,PGA为合适的IM指标;隧道左右边墙处衬砌为震害易损部位,可视作抗震设计的薄弱部位;在Ⅷ度多遇地震水平作用下,隧道结构仅发生轻微损伤甚至保持完好无损伤状态的概率较大,而在Ⅷ度罕遇与极罕遇地震水平作用下,隧道结构发生危及生命安全的严重损伤的概率较大;在相同强度的地震动作用下,近断层脉冲型地震动导致隧道结构发生更为严重破坏的可能性更大,具有更强的破坏性,在隧道抗震设计中,不可忽视近断层地震动的速度脉冲效应对隧道结构抗震性能的影响。

Research on vulnerability of tunnel structures subjected to near-fault and far-field ground motions

Regarding Zheduoshan tunnel,a control engineering of Sichuan-Tibet railway,as the research object,a dynamic time history analysis model is established. Combined with the site ground motion design response spectrum,the near-fault pulse-type ground motions and far-field ground motions are selected for the incremental dynamic analysis of the seismic performance of the tunnel engineering structure. Then,a preliminary discussion of the seismic intensity index IM applicable to the tunnel structure is carried out,and the damage degree of the tunnel structure at different key locations is presented. Afterward,the seismic vulnerability probabilities of the tunnel structure under the actions of the near-fault pulse-type ground motions and the far-field ground motions are compared and analyzed,and the failure probability of the tunnel structure under the actions of the two ground motions at the three-level fortification level is further presented. The results show that PGA is a suitable IM index for the tunnel structure. The lining on the left and right side walls of the tunnel is vulnerable to earthquake damage,which can be regarded as the weak parts for the seismic design. Under the level of Ⅷ-degree frequent earthquakes,there is a high probability that the tunnel structure will only be slightly damaged or even remain intact and undamaged,while there is a greater probability that the tunnel structure will be serious damage to life and safety under the level of Ⅷ-degree rare and extremely rare earthquakes. Under the same intensity of ground motions,near-fault pulse-type ground motions are more likely to cause more serious damage to the tunnel structure and have stronger destructiveness. Therefore,In the seismic design of tunnels,the impact of the velocity pulse effect of near-fault ground motions on the seismic performance of tunnel structures cannot be ignored.