A new “next generation” of shaft enlargement machines for shaft boring using the pilot borehole is now available to the market. The Shaft Boring Machine for Shaft Enlargement (SBE) was developed by Herrenknecht in close collaboration with a joint-venture between Thyssen Schachtbau GmbH and Murray & Roberts Cementation. These two mining services and technology groups had approached Herrenknecht with the aim of applying V-Mole technology to the next high-performance generation of shaft enlargement.
With the newly developed shaft enlargement machine, Herrenknecht offers a modern version of shaft boring machines that “complies with the highest standards of efficiency, safety and reliability.” With this new generation machine, shaft boring diameters of up to 9.5 m can be realised under optimum conditions in hard rock. The machine concept allows significantly higher sinking speeds compared to earlier shaft boring generations. It is robustly designed to handle the tough working conditions found in sinking of shafts. Qualified personnel can easily operate the system.
The SBE basically works like modern hard rock TBMs, but vertically. Advance and primary shaft lining are carried out simultaneously. With the help of laterally extendable hydraulic cylinders the 15 m high and 350 t machine braces itself before every drilling stroke in the shaft steadying the machine, allowing the thrust cylinders to push the rotating cutterhead against the borehole floor. Hydraulic cylinders ensure precise vertical alignment of the shaft boring machine 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 there anchors and steel mesh can be put in place by two powerful hydraulic drill rigs. If required, a shotcrete unit on the shaft boring machine 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 of a shaft with the new SBE occurs in three phases:
– First a pilot hole is created from the top downwards, which sets the vertical target axis
– Once at the bottom, workers in the cavern replace the drill bit with a reamer, which then enlarges the pilot hole from bottom to top until the pilot borehole diameter is reached. The muck is continuously loaded at the foot of the borehole and transported away
– Thereafter, the shaft boring machine enlarges the pilot borehole from top to bottom to the final diameter and installs the primary lining of the shaft in parallel. The shaft depth is only limited by the technically feasible length of the pilot borehole