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Effect of Excavation Blasting in the Arch Cover Method on Adjacent Existing Pipelines in a Subway Station

The dynamic responses of existing pipelines are of great significance to be studied in blasting excavation in the arch cover method. In this paper, the Shi Kui Subway Station Line 5 in Dalian, China, is selected as a case study. A 3D numerical simulation model is established to analyze the dynamics characteristics of the existing pipelines subjected to blasting vibration, with a triangular pattern describing the blast hole pressure. The numerical simulation is verified by comparing the existing pipelines’ PPVs of the numerical model and field monitored points. Then, the dynamic responses of the pilot tunnels, existing pipelines, and secondary lining are discussed. The effects of the later pilot tunnel on the earlier pilot tunnel are remarkable when the relative distance between them is small. Extensive blasting areas and many charges will result in large peak velocities of the existing pipelines in a short time, as well as a decreased distance from the pilot tunnels. However, the hollow effect can change these dynamic characteristics. The implementation of a secondary lining can reduce the existing pipelines’ dynamic responses when the lower rock is blasted. The most adverse position of the secondary lining is the arch foot rather than the arch crown and arch waist; thus, blasting should be carried out at a suitable age for the concrete to ensure the safety of the structures and pipelines.