摘要
目前关于地下结构地震响应的研究中,往往只考虑单次地震的影响,而实际上地震灾害大多伴随着余震的发生,余震对结构造成的增量损伤不容忽视。该文基于相似理论,推导了离心模型与原型的相似关系并构造了主余震序列,设计了主余震序列作用下地铁车站的离心机振动台实验并开展了实验研究。研究发现,余震的再次激励会导致车站顶板开裂以及中柱端部出现严重剪切破坏,中柱变形协调能力不足是影响地铁车站整体抗震性能的薄弱环节。相比饱和砂土场地,干砂场地中的地表沉降及地铁车站结构的破坏更为严重,砂土场地液化会阻碍地震剪切波的传播并减弱车站结构的动力响应。该研究成果为地铁车站结构的抗震设计提供了理论依据,同时丰富了土动力学实验教学案例。
[Objective]The existing research on the seismic response of underground structures and seismic design codes mainly focuses on the impact of a single earthquake.However,in reality,most earthquake disasters are accompanied by aftershocks.After the mainshock,the structure may suffer substantial damage,and the potential destructive effects of aftershocks on the structure must not be overlooked.Meanwhile,subway stations,essential for urban public transportation,have strict requirements for seismic fortification.Therefore,their seismic response under the action of the mainshock–aftershock sequence must be evaluated.[Methods]This study presents a centrifuge shaking table model test of a subway station under the mainshock–aftershock action.According to the similarity theory,the similarity relationships of various physical quantities were derived at a model scaling ratio of 1:60.The site was prepared using Fujian standard sand with a relative density of 60%.Saturated sand and dry sand sites were set up separately.Because a horizontal unidirectional shaking table was used,30%steel sand was added to the site above the model to simulate the inertial force of the overlying soil under vertical seismic motion.The site was equipped with accelerometers,laser displacement sensors,and pore water pressure sensors.The single-story,single-span subway station structure was made of microparticle concrete,and strain gauges were arranged at the positions of columns,slabs,and side walls.The Darfield seismic wave was selected,and the wavelet transform method was adopted to ensure the target response spectrum met the specification requirements.A sequence of seismic motions containing one mainshock and two aftershocks using the repetition method was constructed.The dynamic characteristics of the mainshock–aftershock sequence were the same,with a relative magnitude for peak acceleration of 0.85.A 30-second time interval and a 30-second amplitude of 0.05 g white noise were set between each stage of the earthquake.[Results](1)After the mainshock,the ground surface settlement of saturated sand soil sites was slightly greater than that of dry sand sites.Under the continuous action of multiple aftershocks,the surface subsidence of dry sand sites was greater.(2)When seismic waves propagated upward from the bottom in a saturated sand field,they exhibited a decreasing trend.In contrast,dry sand fields had a greater amplification effect on seismic acceleration.(3)Strain developed at both ends of the middle column in subway stations under earthquake action.Aftershocks can continuously increase the residual strain in the structure.(4)The sudden change in strain observed during the second aftershock and the sustained increase in residual strain corresponded to the shear failure at the top of the middle column and the fracture at the bottom.[Conclusions]The excitation of the aftershock caused multiple cracks in the top slab and severe shear failure at the end of the middle column.Because of the lack of deformation coordination ability,the middle column was a vulnerable member in the seismic performance of the subway station.Compared with saturated sand sites,surface subsidence and damage to subway station structures are more severe in dry sand sites.Liquefaction may hinder the propagation of seismic shear waves and weaken the dynamic response of station structures.The results provide a theoretical basis for the seismic design of subway station structures and enrich the study of soil dynamics.
作者
袁丽
崔振东
张隆基
王苏扬
任国锋
YUAN Li;CUI Zhendong;ZHANG Longji;WANG Suyang;REN Guofeng(School of Mechanics and Civil Engineering,China University of Mining and Technology,Xuzhou 221116,China;State Key Laboratory of Intelligent Construction and Healthy Operation and Maintenance of Deep Underground Engineering,China University of Mining and Technology,Xuzhou 221116,China;Geotechnical Engineering Department,Nanjing Hydraulic Research Institute,Nanjing 210024,China)
出处
《实验技术与管理》
北大核心
2025年第5期97-104,共8页
Experimental Technology and Management
基金
国家自然科学基金面上项目(52378381)
江苏省力学教育教学研究一般课题(2021jslxjy210)
中国矿业大学教改项目独立重点课题(2022DLZD01)。
关键词
离心机振动台
地铁车站
主余震序列
地震响应
模型实验
centrifuge shaking table
subway station
mainshock–aftershock sequence
seismic response
model test
