Cylindrical steel jackets with integrated hydraulic cylinders that are installed during pipe jacking at defined distances apart in the pipe string. These divide the entire pipe string into individual sections, thus reducing the required jacking force on the jacking frame in the launch shaft and enabling very long pipe jacking stretches.

Tunnel lining method using individual precast concrete segments. The individual segments are transported through the completed part of the tunnel and assembled by the erector to form closed rings directly behind the TBM. The TBM is equipped with hydraulic thrust cylinders which push the shield forward from the last built tunnel ring.

Motor-driven mixing arm in the bottom section of the shield in front of the suction pipe for stirring the excavated material mixed with bentonite suspension in Mixshields. It prevents material from settling and cohesive soil from becoming clogged in the shield bottom area in front of the grill and suction pipe.

A lock through which people and/or materials can pass from the atmospheric area to the pressurized area of the TBM. Enables access to the tunnel face to control the cutting wheel, exchange tools or remove obstacles.

See annulus

Cavity between the surrounding soil and the pipe string or the tunnel lining. Is created by the slightly larger diameter of the cutting wheel or cutterhead compared to the pipe string or tunnel structure.

Tool mounting that makes it possible to change the disc cutters from a protected position behind the cutting wheel or cutterhead.

A highly expansive clay. Used in tunnelling technology as a bentonite suspension for slurry-supported methods. Used during tunnelling both as a transport medium for excavated material in the slurry circuit and as a support medium (thixotropic liquid) for the tunnel face.

A tunnel which ends in the ground as a blind alley.

Geological obstacles (mostly single large pieces of rock encountered in sandy or clayey soils).