软土层场地复杂地铁地下车站结构地震反应分析

Seismic responses of a complicated subway underground station in soft soil layers

软土层对地下结构的地震反应具有重要影响,以往已对软土地基中规则矩形地铁地下车站结构的地震反应进行过研究,其规律对于复杂截面地下结构是否适用还需要进一步探讨。通过考虑车站结构侧向、底部分别存在不同埋深、不同厚度软土层时的27种软土层场地,对上层五跨、下层三跨的新型复杂大型地铁地下车站结构地震反应进行分析,揭示了此类异跨地铁车站结构的地震反应特征,初步给出了软土层埋深、厚度变化对此类车站结构加速度反应、侧向位移反应和地震破坏特征的影响规律。结果表明:异跨车站结构两侧或下方一定范围内存在软土层或将减小结构的加速度反应,而当底板以下20 m深处存在软土层时结构顶板的加速度反应则被大幅放大,约为7.88%~12.72%;异跨车站结构侧向位移沿高度的变化曲线具有明显的“阶梯效应”;软土层位于结构侧向时对结构抗震不利,并且当软土层位于下层侧方时结构的动力反应较大,而当软土层位于结构底板下方时能够起到一定的隔震作用。

Soft soil layer has important influence on seismic responses of underground structure.In the past,seismic responses of regular rectangular subway station in soft soil base were studied,but if their laws are suitable for underground structures with complex cross-section needs to further explore.Here,considering there were 27 soft soil sites with different buried depth and different thickness of soft soil layer at the side and the bottom of a new subway underground station structure,seismic responses of this station with 5 spans in its upper floor and 3 spans in its lower floor were studied.Influence laws of soft soil layer buried depth and its thickness on the station structure’s acceleration responses,lateral displacement responses and seismic damage features were deduced preliminarily.The results showed that when soft soil layer exists within a certain range of two sides or bottom of the station structure,acceleration responses of the station with different spans may be reduced;when there is a soft soil layer 20 meters below the bottom of the station,its top acceleration is amplified by 7.88%-12.72%;the station lateral displacement curve changes along the height with an obvious step effect;soft soil layer existing at the station lateral is not good for anti-earthquake of the station;when soft soil layer exists at the station lower floor lateral,dynamic responses of the station are larger;soft soil layer existing below the bottom of the station can have a certain seismic isolation effect on the station.