Deformation Control Of Shallow-buried Loess Tunnel Caused By Excavation And Effect On The Adjacent High-rise Buildings

Subway has unique advantages in alleviating urban traffic pressure due to less occupation of surface space.In recent years,the urban subway construction rapidly develop throughout the country.However,subway lines Subway lines through the city generally.Tunnel construction causes the surface subsidence and impact on surrounding the neighboring buildings due to disturbance of surrounding rock.In order to solve such problems,this paper bases on the engineering of Metro line 4 between Feitian road and Hangtian avenue in Xi’an,through method that combination of field monitoring,laboratory test and numerical simulation,analyzing law of tunnel excavation deformation,control deformation and analysis of the effect of tunnel excavation on nearby high-rise buildings.The main study resutls are as follows:(1)Placement of monitoring point,analyzing data of the ground settlement,vault settlement,horizontal convergence and surround rock pressure to get the influence law of underground excavation of tunnel and surrounding environment,we can know the deformation are mainly concentrated after excavation and gradually stable over time.(2)Determining the parameters through the loess basic experiment and survey report to establish numerical model by using FLAC3 D finite difference software to analyze whole section method,two step,three steps,CD method,CRD method,double wall pilot tunnel method,CRD method is the best construction method in loess area.Optimization analysis of distance between two tunnels,select of excavation steps,circulating footage,distance between excavation face,the length of foot bolt and angle to get parameters applicable to the project.(3)Modeling nearby high-rise building,soil and tunnel as a whole to study the different influential factors of tunnel excavation on nearby high-rise buildings,the results show: Excavating the tunnel away from the construction side will cause smaller effects on buildings.When tunnel buried depth is unchangable,with the change of the distance between the tunnel and building,the pile body horizontal deformation,vertical deformation,axial force and bending moment are constantly changing.When L < 1.5D,the influence of tunnel excavation on nearby high-rise building is the largest;When L = 2D to 3D,the growth rate is small,the tunnel construction on nearby high-rise building effect is relatively small.When the distance between tunnel and construction is unchangeable,pile horizontal deformation is biggest in the buried depth of 3D~4D,the largest maximum pile axial force are mainly distributed in H = 2D ~ 3.5D,the maximum pile bending moment in the buried depth of 3D.When the distance between two Tunnels less than H,the tunnel has large influence on construction.