Study on the interactive dynamic responses between the new-built subway tunnel by blasting construction and the existing operation subway tunnel

Taking the new-built Line 3 metro under-passing the existing metro Line 4 in Shenzhen as the engineering background, numerical simulation was adopted to analyze the interactive dynamic responses between the new-built metro tunnel by blasting construction and the existing operation metro tunnel. The results indicate that under the action of blasting vibration the maximum tensile stress, the maximum vertical displacement and the maximum vibration velocity of the secondary lining for the existing metro tunnel are all located in the center of inverted arch. The maximum vertical displacement and the maximum vibration velocity at the inverted arch, arch foot, side wall and arch crown are successively reduced. The vibration velocity at the center of the inverted arch is beyond the blasting safety control standard when the excavation footage is 1 m. Accordingly, the vibration velocity of the secondary lining for the existing metro tunnel should be intensively monitored during construction. Just to be on the safe side, the excavation footage is suggested to be 0.5 m. The maximum displacement, the maximum additional moment and the maximum additional axial force produced by the existing metro operation on the new-built tunnel is 0.22 mm, 750 N · m and 30 kN respectively. It indicates that the existing metro operation has little impact on the new-built tunnel and that can be ignored in the design and construction of new metro tunnel.