【摘要】 运用FLAC3D对某无衬砌土质隧洞在地震作用下的动力响应进行了研究,根据位移时程及剪应变增量的变化分析了其破坏机制和规律。计算结果表明:地震作用下由于隧洞临空面对地震波的放大效应,在离临空面一定距离的土体初始将产生一定的永久位移,之后随时间开始收敛,此处土体最终保持了稳定状态;而临空面附近的土体则完全处于屈服状态,位移不随时间收敛,一直向临空面滑移,直至破坏;最大剪应变增量首先出现在侧墙部位,随着地震的持续其范围迅速扩大并向拱顶延伸,同时在拱顶也出现最大剪应变区,当拱顶和侧墙最大剪应变区完全贯通时,隧洞就产生了整体破坏;剪应变增量随地震作用的时间而增大,但增长速率随着地震的持续而减小。研究结果为土质隧洞的抗震设计提供一定的借鉴。更多还原

【Abstract】 The dynamic response of an unsupported soil tunnel under seismic loading is investigated by using FLAC3Dcode,its failure mechanism and rule is analyzed according to the change of displacement time histories and shear strain increment.The calculating result shows that the ground in certain distance away from the free face would generate some permanent displacement due to the amplified effect of free face against seismic wave.With the progress of time,the displacement would gradually decrease and finally keep a steady state.More specifically,for the shallow buried tunnel,the stored strain energy is small,and hence the destruction would not happen easily.While with the increasing of buried depth,the strain energy can increase correspondingly,as a result,the tunnel would reach closer to limit state and easier to cause failure.However,the ground near the free face would be completely under a yield state and its displacement would gradually increase before final damage.At the beginning,the largest shear strain increment would happen at the sidewall,while the shear strain area would be enlarged dramatically with the continued function of seismic loading,and finally reach the vault.When the largest shear strain in vault and sidewall has coalesced,this means that the tunnel is completely broken.Even though the shear strain increment would be enlarged with the exertion of seismic loading,its increasing rate would decrease with the time.The conclusion in this paper can be referred to the seismic design of soil tunnel.更多还原