Analysis Of Ground Subsidence Induced By Subway Station PBA Construction

In recent years,subway construction and rapid development,subway station construction process many,of which the subway station PBA method construction with its unique advantages attracted attention by all parties.The PBA method is used as the initial support in the small guiding hole of concealed excavation.the concrete principle is to split the large section cavity into a number of small pilot tunnel excavation,and to apply the " post" column " column" " arch" " beam" frame to form a solid initial support system.under the protection of the initial support system,it can be used as waterproof and permanent two lining in the initial support system of the pile pillar.The PBA method is mainly characterized by strong adaptability,and can well control surface settlement deformation under various formation conditions.compared with the traditional shallow buried excavation method is more safe and reliable,the PBA method can not only reduce the settlement risk of large section and dark excavation construction,but also avoid the complicated process of cover excavation method construction.However,the process transformation of the PBA method is more,the force transformation is complex,and the difference of settlement effect in different formation is also great.According to the influence of PBA method construction on surface settlement in complex clay stratum,the numerical simulation analysis is carried out in this paper,taking the construction project of a subway station in Beijing as reference,according to the simulation results,the layout of the monitoring points of surface settlement of the station is guided.Through collecting the measured settlement data of the standard section encryption monitoring point,comparative analysis of the measured data and the simulated calculation value before,proves that the settlement data obtained by the numerical simulation is consistent with the measured data,and verifies the rationality of the numerical simulation method,and indicates that the numerical modeling method can effectively guide the arrangement of the surface settlement monitoring points of the construction of the PBA method.The ground surface subsidence caused by the excavation stage,pile-arch construction stage and the second lining stage are 16.37 mm,2.91 mm and 18.88 mm,respectively,account for 42.9 %,7.6 % and 49.5 %,respectively,and the key measures to control surface subsidence are discussed in combination with the actual construction situation...