Study on the vibration effect on operation subway induced by blasting of an adjacent cross tunnel and the reducing vibration techniques

The Hongshan road tunnels in Nanjing cross up the metro Line 1 tunnel, the closest distance between Hongshan road tunnels and subway tunnels is only 4.14 m. In order to ensure the safety of the subway structure during the Hongshan road tunnels group excavation blasting, the vibration of the subway tunnel was monitored real time. The monitoring results showed that the main frequency distributions of the radial, tangential and vertical vibration of subway tunnel were significantly different. The main frequency and energy of tunnel vibration is mainly concentrated in the high frequency band. This characteristic is very beneficial for the protection of the subway tunnel and catenary. A series of techniques to reduce the vibration were taken during tunnel excavation blasting, which reduced the impact of the blasting vibration to subway tunnel and catenary, and ensured the operation subway safety. The vibration of subway tunnel can be controlled within a certain safety standard with proposed of reducing vibration techniques. It is shown that real-time monitoring and the comprehensive application of the reducing vibration technique are able to guarantee the security of adjacent cross operation subway, which provides references for similar tunnel projects.