Study On Seismic Response And Applicability Of Design Method Of Subway Station With Aboveground Structure In Loess Site

The research on the seismic response of underground structures such as subways started late,and it has been fully developed since the Hanshin earthquake in Japan.In the past two decades,relatively abundant research results about traditional buried structures have been obtained.However,there was a lack of research on this new or special soil-structure dynamic interaction system with both aboveground and underground structures.Since the seismic response of underground structures is mainly controlled by the deformation of the surrounding soil,the properties of different soils will inevitably have a significantly different effects on the seismic response of underground structures.As a kind of special soil with micro-voids and weak cementation characteristics,the seismic vulnerability of loess is obvious.However,the study of seismic response of underground structures such as subway stations in the loess area is lagging behind,which is because it has just started in recent years and the research results are scarce.Therefore,this paper took the Lanzhou subway construction as the background,and carried out a study on the seismic response characteristics and applicability of seismic design methods for subway stations with aboveground structures in the loess field.The main work and results of the paper were as follows.(1)Based on shaking table tests that take into account soil-structure dynamic interactions,analysis was performed from the fundamental frequency,acceleration response and horizontal displacement response of the model system,strain response of the station structure,and dynamic soil pressure response of the foundation soil.The dynamic response characteristics of subway stations with above-ground structures were systematically studied from the perspectives of the sensitivity of the underground structure and the aboveground structure to the frequency spectrum characteristics of ground motion,the soil-structure dynamic interaction mechanism,and the weak seismic components.(2)The finite element software OpenSees was used to study the numerical simulation of dynamic interaction system between subway station with aboveground structure and loess.At the same time,the dynamic response of the model foundation soil and the model structure in the numerical simulation and the shaking table test results were compared and analyzed,and it was verified that the numerical simulation method could reliably simulate the dynamic response characteristics of the loess foundation and the subway station with aboveground structure.(3)A finite element numerical model of the prototype subway station in the loess site was established.First,the dynamic response characteristics of the prototype subway station were analyzed.Then,the earthquake response of subway stations with aboveground structures was studied in detail from the influencing factors of ground motion loading conditions,structural inertia effects,foundation soil inertia effects,and structural burial depth.The dynamic response of the station structure was mainly affected by the inertia effect of the aboveground structure and the inertia effect of the foundation soil.When these two factors affected a certain equilibrium state,the seismic performance of the structure could be further improved.(4)The inertial force method and the seismic displacement method of the commonly used underground structure seismic design methods were theoretically analyzed and reasonably extended to a certain extent,and then they were applied to the seismic calculation of subway stations with aboveground structures to study the applicability of methods in seismic design,it was found that the seismic displacement method was more applicable overall.