| Loess,as a special type of soil mass,is widely distributed in China and mainly in the northwest.Due to its macrovoid,weak cementation and water sensitivity,loess can suffer from different levels of compaction,seismic subsidence and collapsibility under the influence of soaking and load from both internal and external.The loess' s special sensibility about earthquake makes the loess area suffers a lot more than normal soil type area.Judging from many strong earthquakes occurred in northwest loess area in history,the earthquake can cause huge casualties and property damage.In recent years,with the increasing input to infrastructure construction in our country,more and more subway project appears in northwest loess area.Once the underground structure is damaged by the earthquake,a series of secondary disasters ensue.Meanwhile the rehabilitation expense and the difficulty of construction will be very high.Nowadays,underground space has been massively developed and utilized.To meet the different using conditions,the structure has become very complex.Moreover,there have been frequent occurrences of geological disasters in recent years,most geological disasters become catastrophe.Therefore,the safety problem of underground structure resisting natural disasters draw intensive attention from researchers around the world.Now,the design of anti-seismic in our country's underground structure is a bit lagged,and the research method is imperfect.There still isn't a set of independent design specification aiming at the underground anti-seismic.Researches on the seismic dynamic response in underground structure in loess area are still very rare,which are basically at exploring stage.For this reason,this article,taking the underground structure in one subway station in Lanzhou as real engineering background,carries out a study on the underground structure dynamic response of subway station in loess area.The research result can provide an important reference for the anti-seismic design and engineering practice in loess area's underground structure.To explore the dynamic response under earthquake in loess area's subway station underground structure,this article has done several aspects of work:(1)Made systemic revision and summary of the interactive mechanism,damaging feature,theoretical and experimental research methods of soil-structure,which laid a solid theoretical foundation of exploring the dynamic non-linearanalysis of subsurface structures of subway stations in loess areas under the effect of earthquakes.(2)Simply introduced the frame structure of the finite element software Open Sees,and narrated the difficult points in the process of building finite element model.(3)Built two-dimensional interactive model of soil-structure based on the powerful and open-sourcing finite element software Open Sees.Studied the dynamic responses of the subsurface structures of subway stations in loess areas with different inputs of earthquake waves,and the corresponding response regularities would be summarized.Meanwhile,the dynamic response regularities of subway stations' underground structures,respectively with different material characteristics and station structure densities,are researched in this thesis.(4)Comparatively studied several common soil boxes from every aspect by looking up plenty of references about model casing and shaking table test.The shear soil box was made on the basis of previous studies,and the finite element analysis and experimental analysis on its dynamic property were conducted.(5)Made the scale model of subway station structure on the basis of deeply learning and understanding similarity theory. |
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