ABSTRACT
This chapter introduces the different types of tunnelling works commonly constructed and discusses the various groundwater control methods that can be deployed. The groundwater control options for tunnels are strongly influenced by the typical geometry of tunnel projects. The longest-established method of applying a fluid pressure to the face to exclude groundwater from a tunnel is compressed air working. Compressed air essentially acts to repel groundwater from the tunnel face – it is important to realize that the groundwater must have a pathway to move away from the tunnel. Tunnel driven below groundwater level in permeable strata, and grouting is carried out from the tunnel to treat the ground ahead of the tunnel face. Groundwater levels can be lowered in advance of construction, and the tunnel is driven through ‘dewatered’ ground. Shafts are excavations from the surface and in principle can use the same groundwater control strategies as conventional excavations.
