Study On The Effect Of Strata Deformation During The Construction Of Large-span Shallow Subway Station

National economy is developing fast after coming into the 21 st century,and the problem of population,environment as well as transportation force people to think about the answers for sustainable developing.Building subway lines and light rail has been necessary to infrastructure in big city.Shallow-buried excavation is one of the fastest growing ways to build underground structures,and it has been applied to the constructions of many subway lines as well as other municipal engineering.Shallow-buried excavation is not complex and flexible,the design and construction technology could be modified based on the monitoring to ensure the safety and economy.The practice shows that shallow-buried excavation owns more advantages than NATM and shield driven method,but the construction technology of shallow-buried excavation demands higher quality.In order to ensure the project is safe and implemented smoothly,based on an actual typical large-span subway station this paper uses stratum structure method to build a finite element model with a large finite element software,the structure design and construction design are both same as the actual subway station,this paper analyzed the law of strata deformation caused by the change of the structure system while the surrounding rocks around the subway station are been excavated and the supports are been demolished,the specific contents are as fellows.(1)The deformation law of strata deformation caused by the change of the structure system are been studied while the excavation of shallow-buried subway station happens in different surrounding grade and depth of burial.Results shows that the ground surface settlement and surrounding rock deformation are divided into three stages as tiny deformation,rapid deformation and slow deformation.Different surrounding rock classifications have different effect on the displacement.The buried depth of station increases will expand the ground subsidence trough and reduce the ground surface settlement.(2)The demolition of temporary support will lead to the change of structure system which causes the change of surrounding rock stress and ground deformation.Superior demolition method is elected through comparing different temporary support demolition methods,the superior length of the support demolition is researched,too.(3)The deformation law of strata deformation caused by the change of the structure system are been studied with superior demolition method while the demolition happens in different surrounding grade and depth of burial.Results shows that the demolition happens in ? and ? level of surrounding rock causes larger influence on ground surface settlement and crown settlement than ? and ? level of surrounding rock.While the surrounding grade is same,the demolition happens in greater depth causes larger crown settlement and smaller surface settlement than shallow depth.This paper analyzed the law of strata deformation caused by the temporal and spatial effects on the surrounding rocks around the subway station not only while they are been excavated but also while the supports are been demolished,the research results will provide certain guidance to construction of urban shallow tunnel,shallow subway station and similar engineering projects.