基于静力推覆分析的穿越地裂缝浅埋地铁车站地震破坏模式研究

Seismic failure mode of shallow buried subway station crossing ground fissures based on static pushover analysis

以处于西安f4地裂缝场地的浅埋地铁车站为研究对象,通过开展振动台试验,探讨了地裂缝场地和结构的震害特征。同时,考虑场地地震响应的非一致性,采用静力推覆分析方法,分析了穿越地裂缝浅埋地铁车站的地震破坏模式。结果表明:针对地裂缝场地地下结构的Pushover分析方法能够较真实地反应地震作用下地裂缝场地的活动特征和地下结构的破坏特点。在水平地震作用下,趋于稳定状态的地裂缝上、下盘土体主要进行张合活动(相互挤压与分离)。其中,相互挤压会对结构中柱施加明显附加压弯作用。地裂缝场地土体的水平剪切变形是结构破坏的主要外在因素,而地裂缝活动造成的附加压弯作用会进一步增大中柱轴压比,降低中柱的变形能力,加速结构的地震破坏。在地裂缝场地特征变形作用下,结构底层中柱水平剪切变形能力相对较弱,且结构剪力表现出明显的空间分布规律,上盘结构底层中柱是结构的抗震关键构件。研究结果对该类结构的抗震设计具有重要参考价值。

Here,taking a shallow buried subway station located in Xi’an f 4 ground fissure site as the study object,shaking table tests were conducted to explore seismic damage characteristics of ground fissure site and the structure.At the same time,considering the non-uniformity of seismic response of the site,the static Pushover analysis method was used to analyze the seismic failure mode of shallow buried subway station crossing ground fissures.The results showed that the Pushover analysis method for underground structure in ground fissure site can more realistically reflect activity characteristics of ground fissure sites and failure characteristics of underground structure under earthquake action;under action of horizontal earthquakes,soil bodies on upper and lower discs of ground fissure tending to stable state mainly undergo open-merge activity,i.e.,mutual squeeze and separation where mutual squeeze can exert an obvious additional compressive bending effect on structure central column;horizontal shear deformation of soil body in ground fissure site is main external factor of structural failure,and the additional compression and bending caused by activities of ground fissure can further increase the axial-compression ratio of central column,reduce the deformation capacity of central column,and accelerate seismic failure of structure;under action of specific deformation of ground fissure site,the horizontal shear deformation ability of central column in structure bottom layer is relatively weaker,and structural shear forces have an obvious spatial distribution law,central column of structure bottom layer in upper disc soil body is a key aseismic component of structure;the study results have important reference value for aseismic design of this kind of structures.