Artificial Boundary And Dynamical Response Analysis Of Underground Railway Station In Loess Area

As a significant city in the loess area, Xi an is experiencing a rapid progress of urbanism,the underground rail traffic is developing rapidly, while the researches on seismic response of underground structure such as subway station and subway tunnel are still during the elementary step, the artificial boundary can influence the accuracy of computation.Reasonable artificial boundary can imitate the transmitting progress of wave from near finite field to distant infinite field, while unreasonable boundary would lead to the reaction which is inconsistent with the reality, thus how to choose and build the artificial boundary condition is mainly important to the research on fluctuating value in near field.According to the situation above, this dissertation discusses the operating principle of artificial boundary detailedly. It introduces the theories such as remote artificial boundary,viscous boundary, viscous-spring boundary, consistent viscous-spring boundary and infinite-element transmitting boundary as well as relevant implementation method. In addition,it analyses and evaluates the characteristics and limitations of all boundary conditions.The results showed that the viscous-spring boundary and infinite-element transmitting boundary have the characters of simple technology, low computational cost and high precision; the results of consistent viscous-spring boundary and viscous-spring boundary are similar, but the way of setting remains to be further research.To further the study in employment of artificial boundary in subway station of loess area,this dissertation large-scale finite-element software-ABAQUS, adopts several common artificial boundary methods, build free site model of loess and two-story and two-span subway station structure model, 2D seismic response is also analyzed in this article. This dissertation discusses and summarizes several questions during the underground structure numerical simulation process, for instance, the dynamic characteristics of loess, the elastoplastic damage model of concrete, the setting process analysis step, and the selection of seismic wave. According to the dynamical response of subway station structure, analyses the failure discipline of subway station structure under seismic action. It also compares theexperiment effect under different artificial boundaries, and it presents the setting method of artificial boundary to adjust to the loess geology condition in Xi an.This dissertation studies the numerical simulation of subway station under the loess geology condition, it focuses on exploring artificial boundary in near-field fluctuation values analysis, it has great significance to the seismic research for subway station structure as it provides easy-to-use, accurate and highly adaptable modeling method.