Study On The Effects Of New Metro Station Crossing Under The Existing Peculiar Metro Station In Small Distance

Nowadays,the underground construction is increasing important for the city’s construction and development.under the background large-scale construction of metro rail lines,it’s inevitable to appear the phenomenon of overlap between different metro lines,that is the overlap between subway stations and tunnel intervals.Obviously,the existing metro lines will be encountered by impacts such as tunnel structure deformation,drops of bearing capacity crack and water penetration.In a special case,when the construction of new metro lines are close-spaced under the existing metro lines,the existing metro lines will be influenced by that construction because of it’s characteristics of close-space,fast deformation and difficult consolidate,even worse may threat the security of existing metro lines.Due to the transfer position,distance,underground space conditions and other requirements,it is inevitable for new metro lines crossing with close-spaced under existing metro lines.Therefore,the in-depth research of tunnel crossing has an important significance.Based on sufficient study of domestic and foreign scholar’s research of tunnel crossing,this article select a specific engineering namely new urban rail 16 th close-spaced crossing the existing urban rail 10 th,in combination with theoretical research and numerical simulation.Considering of some aspects which have representative characteristics,for example,the settlement deformation regular of existing structure,bearing capacity of existing structure and it’s deformation-controlled standard.After lots of in-depth research of existing metro lines which under close-spaced tunnel construction,main achieves are as follows:(1)Through systematic summary of mechanics principle of tunnel construction which include single hole and double holes,this article make analysis and research on stress distribution state,degree of stress concentration and development of plastic zone of tunnels because of its excavation.With elastic-plastic theory,make relevant analysis and calculation of double holes which applied support structure after its excavation.At the same time,with the help of software MATLAB,have realized output of results graphics,providing data support for numerical simulation work in the back.(2)Carrying on simulation of the process of new tunnel’s close-spaced excavation with “stratum-structure” model,after taking a choice of contrivance,considering of impacts to the existing metro line such as the settlement deformation regular of existing structure,internal force of structure and structure stress,making optimization analysis of construction factors which mainly include the tunnel excavation footage,pilot tunnel excavation plan and different tunnel excavation sequence,which are foundation of taking a judgement that whether the existing structure is safe.(3)Applying data of the existing structure’s additional deformation as forced displacement on structure’s lateral springs in “load-structure” model,making results of additional forces of structure because of its additional deformation.Making a judgement of the existing structure’s security after having a comparison of additional forces and structure’s bearing capacity.(4)According to the above achievements,this article formulate deformation-controlled standard of existing metro line’s structure which include station structure’s standard and track structure’s standard in crossing engineering.Station structure’s standard mainly take the existing structure’s bearing capacity and the influence of crossing engineering into account,which depends on the above calculation and analysis woks.While the track structure’s standard rely on subway line principle of daily maintenance and repair available,meanwhile the former is subject to the latter.(5)When drafting deformation-controlled standard of existing metro line’s structure,it is important to observe principle of different areas,stages,groups and classes.There are corresponding deformation-controlled standard for each step in a typical construction process,only every step of the typical process of deformation under control,thus can ensure that the finally deformation of existing metro lines is effectively control.