Surface Deformation Law And Control Technology Of Fully Excavated Construction Of Guangjijie Subway Station By PBA Method

It is of great engineering value to carry out research on ground settlement law and control technology of underground excavation construction of metro stations in loess area.This paper relies on the construction method of the tunnel pile method of Guangjijie Station in Xi’an Metro(That is,Pile-Beam-Arch,referred to as PBA),which combines theoretical analysis,numerical simulation and on-site monitoring.Study on the law of surface deformation induced by full excavation construction of Guangjijie Station,The main work and conclusions are:(1)The design calculation model of the PBA method side pile of the metro station in the collapsible loess area is established.Deriving the formula for calculating the internal force of the side pile,The design calculation method and flow of PBA method side pile in loess area are given.The safety evaluation of the side piles at Guangjijie Station was completed.(2)Based on the MIDAS finite element software,the parameter sensitivity analysis of different excavation footage,different side pile embedding depth and side pile diameter,and different steel pipe column diameter and spacing were studied.Based on the minimum control of ground surface settlement,reasonable excavation footage,side pile embedding depth and side pile diameter,steel pipe column diameter and spacing are suggested.(3)Based on the reasonable excavation footage,the depth of the side piles and the diameter of the side piles,the diameter and spacing of the steel pipe columns,the surface settlement law induced by the whole process of station PBA construction is predicted.The surface settlement characteristics of the tunnel during the excavation stage,the beam-column system application stage,the buckle arching stage,the station floor layer application stage and the platform stage application stage are analyzed.(4)The design of the surface and tunnel deformation monitoring program for the construction of the PBA method at Guangjijie Station was completed and on-site monitoring was carried out.The monitoring results show that the results of finite element prediction of tunnel and surface deformation in different construction stages are basically consistent with the actual monitoring results.