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Extreme Ingress: Managing High Water Inflows in Hard Rock TBM Tunneling

Managing water inflows is not new to TBM tunneling, but today there are an increasing number of methods and best practices to handle potentially high water inflows efficiently and safely. High volumes of water can be safely contained or managed in hard rock TBM tunneling, but this requires the proper foreknowledge and planning. This paper outlines how machines can be designed ahead of time for expected high water, and how risk can be mitigated during tunneling. It also covers the importance of pre-planning and includes a look into the future of water control methods. Case studies of hard rock tunneling with heavy water inflows are examined, with a focus on New York, USA’s Delaware Aqueduct Repair, the 3.8 km long bypass tunnel below the Hudson River requires excavation through limestone rock at water pressures of up to 20 bar. A unique 6.5 m diameter Single Shield TBM, sealable for high pressure excavation, is boring and lining the tunnel.

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