Space for new traffic infrastructure above ground is scarce all over the world which is why such structures are increasingly being built underground, for example, in Hong Kong, where space for new structures is also becoming scarce underground. The route plans for the “Hong Kong Kowloon Southern Link” were accordingly unusual: the two parallel tunnels start off side by side, then run one on top of the other only to return to their parallel design in the target shaft.
With a diameter of almost eight meters, the section design demands maximum precision from the S-335 Mixshield when boring only three to four meters away from building foundations is involved. In order to avoid settlement an EMC (Electronic Muck Control) system is installed on the TBM. This software compares the actual excavation volume conveyed with what has been calculated in advance and triggers an early alarm upon defined deviations. On March 12, 2008, the Herrenknecht Mixshield achieved its final breakthrough in a mere 18 months with the requested precision. Up to 100 meters a week were excavated through granite.