Tunnel shafts are vertical channels that link the surface of the ground to the upper part of a tunnel during the tunnel’s construction.
Generally, shafts are constructed from the ground surface down, using conventional shaft sinking methods. However, in rock tunnelling projects, shafts not used for primary construction access can be constructed using raise boring. In raise boring, a mall pilot hole is drilled from the ground surface to tunnel depth. A reaming bit is then used to excavate the shaft to final dimensions.
Several methods are used to support shafts excavated in soil during construction. Some support systems are installed from the ground surface prior to the start of excavation. Others are installed concurrently with excavation(Shaft Design, n.d.).
What makes starting these underground arteries such a complex and vital undertaking? Share your initial thoughts!
