Study On The Control Of Subway Station Constructed In PBA Method

With the progress and development of urban underground space technology and rail transit,PBA(Pile-Beam-Arc)tunneling method,as a kind of shallow buried excavation method,has been applied more and more frequently in the engineering cases with poor formation conditions and large cross sections.PBA tunneling method,with good development potential and promotion value,has shown significant economic and social benefits in the construction of the metro in Beijing,Xinjiang and other areas.Thus it is necessary to study on the influence laws of surface subsidence and deformation based on construction process and other construction factors.Nonlinear finite difference software FLAC3D was used to analyze and simulate in this thesis,combined with engineering example of Urumqi Metro Line One metro station with PBA tunneling method,obtaining the influence that different tunnel construction process and pilot form have on formation and structure.The main results and conclusions of this thesis are as follows:1)Based on Urumqi Metro Line One metro station project in Xinjiang,this thesis studies the advantages and disadvantages of the PBA tunneling method excavation scheme of 4,6,8 pilot form,under the premise of the buried depth,station size and surrounding rock properties of station analysis.2)Through the evaluation index analysis of surface subsidence,stratum displacement,ground stress distribution,formation plasticity,safety factor of surrounding rock and tunnel lining structure safety,this thesis obtains that the4pilot form is the optimum selection.3)This thesis studies the process optimization research of the four construction excavation procedure under the4pilot form metro station excavation scheme,such as"upper-lower,central-edge","upper-lower,edge-central","lower-upper,central-edge","lower-upper,edge-central".Based on three dimensional numerical simulation analysis,the comprehensive evaluation method is adopted to comprehensively evaluate the index such as ground settlement,stratum displacement,stress distribution,formation plasticity,and mechanical properties of subway station structure.Finally "upper-lower,edge-centrar" is the best construction process,so as to guide the construction.4)The internal force and stress distribution of steel pipe pile of enclosure structure in every stage of excavation are studied.The influence of different pile diameters and pile spacing is compared,according to the6indexes of axial force,peak value of moment,peak value of transverse displacement,maximum value of ground settlement,maximum value of crown settlement and bottom plate's upheaval the best scheme is obtained.