TBM Tunneling - Rock Mechanics Based on an Anisotropic Jointed Rock Model - page 665

The interface between the segmental lining and the excavation contour - the so-called
“annular gap” - is normally grouted with mortar using injection lines which are inte-
grated into the tail skin (Fig. 21.2). The mortar in the annular gap leads to a bedding
of the segmental lining which is maintained to a large extent also after setting of the
grout. Instead of mortar grouting it is also possible to inject gravel into the annular gap
pneumatically via openings in the lining segments.

Figure 21.3 Segmental lining (Wittke et al. 2006)

Between the shield skin and the segmental lining a tail skin sealing is mounted to avoid
leakage of the annular grout into the machine area (Fig. 21.2).
Figure 21.4 shows the working cycle of a shielded TBM, which consists of the phase
of advance designated as “stroke” and the installation of the segmental lining. During
boring the thrust cylinders push the shield forward (Fig. 21.4, upper). After the end of
the stroke the boring is interrupted and the segments are installed (Fig. 21.4, lower).
During installation, the jack of the corresponding segment is retracted and, when the
mounting is completed, extended against the segment. After the assembly of the last
segment of the ring the new stroke begins.

Figure 21.5 shows a shielded TBM with slurry face support also referred to as “mix
shield”. The slurry consists of a suspension containing clay powder or bentonite. The
density

ρ s and unit weight γ s of the slurry can be adapted to the ground conditions

within a certain range.