The Study And Application On The Shallow Burying Method Of Nanguan Station In Changchun Subway Line 2

With the rapid development of city,the above ground space tends to be saturated.urban subway is the best way to solve the problem.Changchun subway line 2 is from Yuanjiadian station in the west to Rainbow Plaza Station in the east.which is basically along the underground of Jiefang Road.Jiefang Road is one of the east-west main roads in Changchun.Especially in the vicinity of Nanguan Station,the traffic is very busy and there is no condition for traffic diversion.Therefore,.buried-tunneling method is the best way to the construction.This paper collects data about settlement deformation and stress monitoring during the construction of Nanguan Station in Changchun metro line 2.Analysing the main structure and formation conditions of construction.Combining the difference method in subway construction from both theoretical and practical aspects.Finding the best construction method in Nanguan Station by simulating the longitudinal tunnel step pitch with the help of the numerical simulation and proposing reasonable control measures.The experimental results are followed:(1)Nanguan Station is located at the intersection of Jiefang Road and Dajing Road,which has a large traffic volume,complex underground pipelines,and many high-rise buildings in the vicinity.Based on the actual situation on the site,the excavation method is initially proposed as PBA method or one-time arching reverse construction method.(2)Simulating the surface deformation of each construction stage of one-time arching reverse construction method and PBA method by numerical simulation method,comparing the settlement of each construction stage and final deformation.The simulating results of one-time arching reverse construction method show that the biggest settlement in construction happened in No.10 guide hole,which accounted for 59.14% of the total.When the work finished,the max of settlement is62.9mm.So it is the point to control the settlement of this period.The simulating results of PBA method show that the biggest settlement inconstruction happened in buckling stage,which accounted for 42.65% of the total.The settlement is bigger than one-time arching reverse construction method,it also increase the difficult of construction,and problem of secondary buckle may be harmful to construction.When the work finished,the max of settlement is74.8mm,which is 11.9mm more than before.(3)Contrasting the construction method,the construction of apex of arch and foundation can be settled in one time and improve the integrity and stability of the structure,which is better than the traditional PBA method.It is easy for workers to install pile foundations and reinforcement lashing,formwork reinforcement and rafting by one-time arching reverse construction method because the bigger construction work surface,what is more,There is enough time for template reinforcement in the installation of the beam and avoiding cracks.In summary,we choose one-time arching reverse construction method in the construction.(4)Simulating different footage program(3 meters/6 meters/9 meters/15 meters at a time)in tunnel longitudinal tunnel excavation by simulation.Conclude the result through three aspects,including settlement value,stress distribution and distribution of soil plastic zone,choosing 9 meters at a time as the best program.(5)By comparing and analyzing the numerical simulation results with the on-site monitoring data,we can conclude that the deformation of the surface caused by the tunnel excavation stage by one-time arching reverse construction method is significant,and the causes are analyzed,and analyzing the reasons and proposing solutions.