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摘要
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.
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