接收端主体结构板施作时机对盾构接收施工影响分析

为探究车站接收端主体结构不同施作时机条件下盾构接收对地表沉降、围护桩及结构端墙侧墙变形的影响规律，依托西安地铁14号线某区间盾构接收施工工程，采用有限元数值模拟方法对车站盾构接收端主体结构不同施作时机条件下（底板施作完成后、中板施作完成后、顶板施作完成后）盾构接收时的地表沉降及桩体变形进行对比分析;在此基础上进一步研究不同位置钢支撑轴力变化对盾构接收时位移变形的影响，并结合现场数据进行验证。研究结果表明： 1）车站接收端主体结构中板施工完成后盾构接收对周边地表沉降及围护桩变形影响最小，此时地表最大沉降位于端头洞口上方，桩体竖向呈沉降趋势且水平向临空面位移。2）围护结构第1、2道支撑轴力变化对盾构接收后地表沉降及围护桩变形影响较大，且随着支撑轴力的增大，地表沉降及围护桩横向变形明显减小。3）在确保支撑轴力满足安全限值的条件下可以适当增大支撑轴力，以控制盾构接收引起的地表沉降及桩体变形。

Influence of Construction Timing of Shield Receiving End Structure on Shield Receiving Construction

To explore the influence of shield tunnel receiving on ground settlement, retaining pile, and structural end sidewall deformation under different construction timings of the station′s main structure of the receiving end, a case study is conducted on the actual situation of the shield tunnel receiving construction project in a section of Xi′an metro line 14. The finite element numerical simulation method is employed to analyze the ground settlement and pile deformation of the shield receiving end under various construction timing conditions (i.e., after the completion of the bottom plate, the middle plate, and the roof) when the shield is received. On this basis, the influence of the change of the axial force of the steel support at different positions on the displacement and deformation of the shield during receiving is further studied, and the verification is carried out in combination with the field data. The research results show the following: (1) After the completion of the mid slab construction of the main structure at the receiving end of the station, the shield receiving has the least impact on the surrounding surface settlement and the deformation of the retaining piles. The maximum surface settlement is located above end tunnel portal, and the horizontal displacement occurs to the pile body and it develops toward free face displacement. (2) The change of axial force of the first and second supports of the retaining structure has a great influence on the surface settlement and the deformation of the retaining pile after shield receiving, and the surface settlement and the lateral deformation of the retaining pile significantly reduced with an increase in the support axial force. (3) The axial force can be rationally increased to control the surface settlement and retaining pile deformation.