沉管隧道地震响应的影响因素分析

以南京长江沉管隧道为背景,采用动力有限元法分析沉管隧道的地震响应。沉管隧道二维分析的合理计算范围分析表明,横向半宽取3倍洞径为宜。隧道结构的地震响应随着周围岩土的黏聚力及内摩擦角的增大而增大。沉管隧道的地震响应随着埋深的增加而增加,但增加幅度在减小,因此,从抗震的角度讲沉管隧道宜浅埋,但浅埋必须满足抗浮稳定性、安全性等要求。在水平地震力作用下,沉管隧道4个角的动力反应较大,是结构的薄弱部位,在设计中应予以加强。考虑水的耦合作用时,隧道的地震反应增强,在水深20 m条件下,应力增量最大超过10%。实际工程中水深一般较大,因此,计算中应该考虑水的影响。

Analysis of the Affecting Factors for Seismic Response of Immersed Tunnel

Taking Nanjing Changjiang Immersed Tunnel as an example,the paper analyzes the seismic response of immersed tunnel by dynamic FEM.The analysis of the reasonable calculating range for two-dimensional analysis of immersed tunnel indicates that the appropriate half transverse width is three times of the diameter of the tunnel.The seismic response of immersed tunnel increases with the increase of coherence and angle of internal friction of ambient stratum.It increases with the increase of buried depth,but the increase range reduces,so immersed tunnel is buried shallowly appropriately on account of seismic restraint on the basis of floating-resistant stabilization.When undergoing horizontal earthquake force,the dynamic response of the four corners of immersed tunnel is greater,so the corner is the weak part and should be reinforced in design.When taking into account the coupling of water and structure,the seismic response of immersed tunnel enhances,the maximum stress increase exceeds 10% when the water depth is 20 m.Water depth is greater commonly in practical engineering,so the influence of water should be considered in calculation.