Study On The Deformation Of Existing Structures Of Subsurface Excavation Metro Station

With the development of urban rail transit,the conditions of subway station condition become more and more complex,the shallow mining PBA construction method not only on the surface settlement control has a good effect,but also the construction method has the characteristics of flexible.Many of subway station construction choose the construction method.Dueing to the pilot tunnel excavations Subway station PBA construction will aggravate the surface subsidence and the existing station deformation.However,the pilot tunnel excavations sequence does not have a clear answer.Considering the factors such as surface subsidence,deformation of station and structural state,researching the influence of the pilot tunnel excavations sequence,has a high practical significance.The reserch based on the Beijing Metro Line 6 Pingguoyuan station,using PBA8-pilot tunnel excavation program.Because of the larger cross section and the closer distance between the pilot tunnel,the interaction of the excavation will be increasing.The MIDAS-GTS finite element software is used for simulating the excavation method of eight pilot tunnel in PBA method,and analyzing the excavationnal influence of the surface and existing station settlement.Mainly carried out the following aspects:(1)After analyzing the whole process of PBA construction,we analyze the surface subsidence of each construction stage,disscus the main factor caused the surface subsidence under the engineering geological conditions.(2)Comparing of the first excavation of the upper pilot tunnuls and the first excavation of the lower pilot tunnuls to the surface settlement and existing station deformation,which determines the pilot tunnul excavation program.(3)By simulating the method of excavating pilot tunnuls in the same peer,dissuss about the advantage of excavating the side pilot tunnuls and the excavation intermediate pilot tunnuls.Analyze how to control the surface settlement at the centerline and the force of the key part of the pilot tunnel status.(4)Under the influence of the pre-reinforcement treatment,the influence of the excavation distance between the pilot tunnel.Dissussing stiffness equivalent principle simulated grouting lifting technology influence the settlement of the land and the safety of the existing station.Compared the simulation results with the actual monitoring data,evaluate the accuracy of the model is established.