Analysis Of Impact On The Environment By Air Channel Construction And Assessment Of Construction Risk

As the contradiction intensified between the increasing urban population and the limited bearing capacity of transportation, the urban subway gets gradually popular by city builders. This paper is mainly studied the stress and deformation of the supporting structure of no.1air channel at Shuang Jing station of the no.7subway in Beijing, and contained the influence to the surface and existing air channel. Numerical simulation was combined with field monitoring in analysis, and evaluating the security risks is added. The main contents of this paper are as follows:Two kinds of construction methods of CRD and PBA is adopted by using finite difference method to no.1air channel, and the calculation results of displacement are compared. The maximum surface sedimentation is10.25mm and12.30mm by two methods respectively. It is found that both of settlement regularities of the surface were curved of horizontal sedimentation conform the Peck by two construction schemes, while the longitudinal surface subsidence rule were processed to present their periodic changes. The first part of the excavation will cause greater degree of surface subsidence.The supporting stress of two kinds construction schemes by finite difference methods. Supporting structure is given priority to with compressive stress when CRD construction method is used, and middle rails and the side wall in the compressive stress is larger,6.86MPa. While the tensile stress in the bottom plate is smaller. Supporting structure maximum tensile stress is produced6.44MPa when PBA construction method is used, and maximum compressive stress is produced6.44MPa. The comprehensive comparison plan CRD is superior to the conclusion of the PBA.The four monitoring cross section was taken in air channel, and risk monitoring on site measurement data and numerical results were analysed comprehensive comparative. The surface horizontal sedimentation and longitudinal settlement distribution trends are both consistent by two methods. It is proved that the numerical simulation of parameter selection is reasonable. The maximum ground settlement was26.3mm, and each section settlement groove width was between6.8～8m. It has hysteresis both the horizontal constringency and arch sedimentation to monitor. The horizontal constringency settlement account is about67%of the total settlement by Regression analysis, and air tunnel vault subsidence has already begun when the construction constraints In front of the constraints to monitoring about0.8～1.2times of hole diameter.(4) The risk evaluation was executed by extension method to air duct construction by CRD method. The air channel construction landslide risk level is calculated with a magnitude of2.4, was moderate risk. It is confirmed that the results of numerical calculation is reasonable by the risk theory, and CRD method was feasible.