Collaboration develops shaft boring technology 23 July 2014

A new generation of shaft enlargement machines is introduced to market by Herrenknecht in collaboration with mining specialists Thyssen Schachtbau and Murray & Roberts Cementation.

The Shaft Boring Machine for Shaft Enlargement (SBE) applies existing V-Mole technology to the next generation of machines. The new technology enables vertical excavation diameters of up to 9.5m in optimum conditions in hard rock. The manufacturer claims the technology enables a time saving of 20-30% compared to conventional methods, with depths limited only by the technically feasible length of the pilot borehole.

Fig 1. Three stages of excavation for the new SBE system

The SBE works like a modern hard rock TBM, but vertically. Advance and primary shaft lining are carried out simultaneously. Using laterally extendable hydraulic cylinders the 15m high x 350 tonne machine braces itself before every drilling stroke in the shaft, steadying the machine and allowing thrust cylinders to push the rotating cutterhead against the borehole floor. Hydraulic cylinders ensure precise vertical alignment of the SBM to the target axis. This is constantly transmitted to the machine operator by a laser-aiming device.

The rotating anchor platform is located on the drilling deck above the cutterhead. From here anchors and steel mesh can be erected by two powerful hydraulic drill rigs. If required, a shotcrete unit mounted on the SBM secures the shaft wall immediately after exposure of the rock outcrop. The machine operator controls all operations safely and conveniently from the interior of the machine.

The sinking cycle runs continuously and is not interrupted by drill + blast times or dispersal of explosion gases. It runs in three phases (Fig 1).

• A pilot borehole is drilled which sets the vertical target axis.
• A reaming bit extends the diameter of the pilot borehole, with spoil removal taking place from within the tunnel.
• The SBM enlarges the borehole to its working diameter, installing the primary lining as it excavates with spoil removal again taking place from below, inside the tunnel.

The new machine is developed by Herrenknecht as a direct response to an approach from mining experts Thyssen and Murray & Roberts, with the collaboration demonstrating further evidence of the mining industry’s increasing utilisation of civil tunnelling technology and expertise.