Research On Construction Scheme Optimization And Monitoring And Measurement Of Large-Section Multi-Dimensional Stereoscopic Station Undercover Under Complex Conditions

With the continuous development of China’s rail transit industry,new problems and challenges have also emerged in the subway construction project.One of the biggest problems is the construction of a new subway station that is closely attached to an existing subway station.Therefore,it is necessary to analyze the mechanical responses of the stratum and the station,such as the displacement field and stress field,when the new subway station is closely attached to the existing subway station.characteristics are analyzed.Based on the engineering background of Beijing Metro Line 6 Ping Guo-yuan Station,which is closely attached to the existing Metro Line 1 Ping Guo-yuan Station,this paper reveals the mechanical response law of the stratum and the station when the new subway station is closely attached and penetrates the existing subway station.Using the method of theoretical research combined with numerical simulation,through the comparative analysis of four commonly used underground excavation construction methods for subway stations,the construction method of the new subway station is optimized from the qualitative and quantitative perspectives.The influence of factors such as the staggered distance of tunnel excavation and the excavation method of pilot tunnel on the surface subsidence and the structural deformation of the existing station,an optimization study was carried out on the excavation scheme of pilot tunnel;finally,the accuracy of the numerical simulation and the above-mentioned The correctness of the research conclusions.The main research contents of this paper are as follows:(1)Through the analysis of the existing research data,it is concluded that the four commonly used underground excavation construction methods for subway stations in Beijing are the middle tunnel method,the side tunnel method,the column tunnel method and the PBA method.The applicable conditions and scope of the four common methods of underpass construction are obtained,and the four construction methods are further analyzed from the aspects of construction economy,construction applicability,and construction safety by using the AHP.Finally,the comprehensive control of surface settlement and control The construction cost is judged from two main angles,and the optimal construction method of this project is preliminarily determined as the PBA method.(2)Using Midas GTS NX three-dimensional finite element numerical analysis software,a three-dimensional analysis model of a new subway station underpassing an existing subway station without considering pre-reinforcement measures was established.The whole construction process of the four excavation methods is simulated,and the mechanical response laws of the stratum,the new station and the existing station caused by different construction methods are revealed.Structural deformation,support structure stress and surrounding rock plastic zone size and other indicators determine that the optimal construction method of this project should be the PBA method.(3)Aiming at the problem of group cave effect caused by the construction of cave groups,this paper adopts the method of orthogonal numerical experiment,and comprehensively considers different excavation methods of pilot holes in the PBA method,excavation sequence of pilot holes,excavation section distance of pilot holes and excavation staggered distance of pilot holes.Based on the influence of four influencing factors on the surface subsidence and the structural deformation of the existing station,16 three-dimensional analysis models of pilot tunnel excavation were established,and the influence laws of different pilot tunnel schemes on the stratum and the existing station were obtained.The degree of influence of the four influencing factors on the deformation of the surface and the existing station was sorted by the range analysis method,and the comprehensive judgment was made,and the core soil method was finally determined as the excavation method of the pilot tunnel(the core soil height reserved for excavation was 1.5m).;The excavation sequence of the pilot hole is first down,then up,first side and then middle;the optimal pilot hole excavation plan is that the excavation staggered distance of the pilot hole is 10 m and the excavation section distance of the pilot hole is 2m.(4)In view of the construction problem of large-section multi-dimensional threedimensional stations under complex conditions,a conventional monitoring scheme and a remote intelligent monitoring scheme for existing stations are formulated.Through the analysis of monitoring data,it is obtained that the actual close-fitting underpass construction will affect the surface settlement and existing stations.The structural deformation law,through the comparative analysis with the numerical simulation results,verifies the accuracy of the numerical simulation results and the correctness of the above research conclusions.