Study On Influence Of Blasting And Excavation On Existing Tunnel By Adjacent Tunnel And The Safety Assessment

With the rapid development of our national economy and transportation,the existing road,bridge and tunnel traffic has been unable to meet the growing demand for transport,the development of the underground interchange project provides a new platform,the underground interchange buildings as a solution to the growing transport needs a new direction.Now more and more engineering practice shows that the new tunnel due to topography,geology and other factors,has been more and more close to,and even through the existing tunnel.The new tunnel in the construction process,will inevitably affect existing tunnel lining structure deformation and stress.If this is not systematic and scientific research and puts forward relevant measures,then in the construction of the new tunnels may will destroy the existing tunnel structures and endanger people,safety,causing unnecessary economic losses.In this paper,Guiyang City,Guizhou Province North train station tie line No.3tunnel under wear Feng tunnel and face to face mountain tunnel project to rely on,the tunnel caused by excavation of the existing tunnel settlement and stress and blasting construction on the lining dynamic effect and other issues were studied.Tie line No.3tunnel left and right hole respectively under wear big Feng and in the face of a mountain tunnel,and Feng tunnel vertical distance of only 18.6m,and face to face mountain tunnel vertical distance 32 m,Tunnel No.3 and Feng,face to face mountain tunnel cross section near the stress situation is complicated,the difficulty of construction.Using the finite element software ANSYS numerical simulation and analysis of the tunnel on the role and scope of the existing tunnel,and the simulated data and the measured values are compared and analyzed.The results show that the measured value is in good agreement with finite element simulation.The simplified model and the geological condition,through the study of No.3 tunnel construction gradually beneath the existing high-speed railway tunnel,this paper found that:1.Through tunnel excavation will have an impact on the surrounding rock,influence range of about three times the diameter of the hole room and due to the existing tunnel below the new airport surface,tunnel lining and surrounding rock will be towards the new airport surface direction and distance of the airport surface closer,then both tunnel lining deformation is large,both tunnel structure subsidence trend is "W".2.the existing tunnel lining stress decreases in the cross section near the intersection,away from the larger,smaller changes in 3 times of the diameter of the tunnel area;the stress decreased gradually by large area,stress produces a small range of concentration.3.High speed rail tunnel near the No.3 tunnel face construction,the blasting construction on Affecting larger,when the excavation face away from the existing tunnel blasting construction of tunnel lining has little influence on the existing tunnel lining;4 when the distance from the explosion source is located at 25~55m,the blasting has a great influence on the measuring point.With the increase of the distance,the vibration velocity of the measuring point decreases rapidly.When the distance from the explosion source distance is greater than 60 m,the vibration velocity of each measurement point is less than 1.5cm/s.