The Research Of Surface Subsidence Of Subway Station Constructed By The PBA Method

As the urbanization level goes up continually in China,the urban population and urban scale keep growing,resulting in more and more traffic problems,such as traffic jam and accidents.These problems can not only block the urban economic progress,but also greatly influence people’s daily life.Under this circumstance,developing urban subway is an important means to solve the urban traffic jam.Over the years,many cities in China have been involved in building a large number of subways,making the subway scale enlarged.In the meantime,problems have emerged in endlessly.For instance,the surface settlement is caused if the subway is constructed in the center of the city,which directly threatens the safety of the surrounding buildings and underground pipelines.Therefore,it is an urgent need to control surface settlement in the construction process and to ensure the safety in these aspects.A rapid growth is witnessed in the subway construction,which is typically reflected on the previously open excavation to the current shallow-covered excavation method.The latter is nowadays widely used in the subway station construction owing to the better control of surface settlement,strong stratum adaptability and high construction efficiency of PBA method.In order to find out the effect of PBA method on surface settlement,the paper takes the actual project at Apple Garden South Road Station,Line 6 of Beijing subway as research object.By using the finite element analysis software—Midas-gts,numerical simulation analysis is made for the whole process of PBA construction.And,the effect of PBA process on surface settlement is analyzed based upon the actual monitoring measurement data.The main research contentsare as follows:(1)A brief summary is made on the key construction points and procedures of PBA method when applied in subway station.(2)Monitoring measurement data are analyzed,and meanwhile the influence of PBA method on surface settlement is researched.(3)Midas-gts is adopted to simulate the data in subway station construction;combining with field monitoring data,the impact of each construction procedure on surface settlement is mainly explored.(4)The influence of different pilot heading excavation sequences on surface settlement is analyzed,thereby reaching the optimal excavation scheme by PBA method.