TBM Tunneling - Rock Mechanics Based on an Anisotropic Jointed Rock Model - page 714

Figure 21.57 Segmental lining in soil, loading and bending (Wittke 2012)
Reduced bedding of the segmental ring
For the five TBM-driven tunnels of the new railway line between Genoa and Ventimi-
glia, which was reported in the previous section, annular gap grouting was carried out
only in the invert directly at the tail skin, whereas at the sidewalls and the roof the annu-
lar gap grouting was carried out through holes existing in the segmental lining at larger
distance from the tail skin. Therefore, additional FE analyses with reduced bedding of
the segmental ring became necessary. These analyses were carried out assuming differ-
ent lengths of grouted sections in the annular gap (Wittke et al. 2006, Wittke-Schmitt
& Lorenzo Martin 2006).
Figure 21.58 shows details of the discretization of the FE-mesh used for these analyses.
A segmental ring loaded due to self-weight which is bedded only at the invert was con-
sidered. Large displacements of 19 cm at the roof and 16 cm at the sidewalls resulted
(Fig. 21.59). As a consequence, the longitudinal joints at the sidewalls open, so that
there is the risk of leakage.