Study On Mechanical Response Of Construction Of Adjacent Power Tunnels Through Existing Stations

In today's world,there are many outstanding problems,such as the shortage of land resources and the clutter of urban development.To solve these problems,the development of urban underground transportation is an inevitable direction.Due to the denseness of urban transportation network lines and buildings,proximity problems often occur in the construction of subways.The construction of proximity tunnels will inevitably deform the surrounding stratum,and the deformation is transferred to the existing structure,which will cause the existing structure to bear additional stress and deformation.Or the deformation exceeds the allowable value of the existing structure,it will cause damage and increase the existing damage,affect the structural safety and even occur a safety accident.Therefore,carrying out the analysis and research of the impact of the new tunnel construction on the existing important structure has become an important and unavoidable problem in the current underground traffic construction.Based on the engineering example of a proposed power tunnel in Beijing passing through an existing station,this topic analyzes the settlement,difference and internal force of the structure during the excavation of the power tunnel,and ensures the station structure during the construction of the power tunnel.Security.The main results achieved are as follows:(1)Aiming at the special situation of the power station near the existing station structure,by establishing a three-dimensional numerical model,the lateral and vertical ground settlement along the excavation of the tunnel and the deformation characteristics of the station structure with different excavation steps of the newly built tunnel are analyzed,and the conclusion is drawn:After the excavation of the power tunnel,the trend of ground subsidence along the lateral direction of the newly constructed tunnel is consistent with the settlement law of the Peck formula.The maximum settlement occurs near the centerline of the power tunnel,with a maximum value of-4.631mm,which meets the control standard of40mm.The width of the sedimentation tank is 6 to 7 times the diameter of the hole.Affected by soil unloading,a bulge occurs at the arch of the station structure with a maximum value of 2.0628mm,which meets the control standard of 10mm;tunnel excavation causes horizontal displacement of the station structure to the left(in the opposite direction of the excavation),The horizontal displacement of the left wall first increases and then decreases,and the horizontal displacement of the right side wall has been increasing.(2)According to the special situation of the construction of the 6~#inspection well,by establishing a three-dimensional numerical model,comparing and considering the impact of the construction of the 6~#inspection well on the ground surface and the structure of the station,it is concluded that Surface subsidence was limited by inspection wells,increasing by only 8%.The construction of the inspection well increased the orbital uplift of the orbit near the inspection well by 20.47%,and the maximum uplift was 1.242mm,but the deformation still met the requirements of Appendix B of the Technical Specification for Safety Protection of Urban Rail Transit Structures.(3)According to the internal force calculation of the construction scheme of the upper-passing power tunnel,the flexural and shear capacity changes of the cross-section and longitudinal section of the station structure were analyzed,and the conclusion was drawn that the internal forces of the station structure were within the limit state range.The minimum safety of shear capacity is 23.81%,and the safety of the station structure is high.