TBM Tunneling - Rock Mechanics Based on an Anisotropic Jointed Rock Model - page 696

Figure 21.34 Case A, displacements at the temporary face and the tunnel contour (Wittke et al. 2006)

The application of an additional supporting pressure of 1 bar at the temporary face
leads to a significant reduction of the displacements. In case B, the displacements at
the temporary face are smaller than 30 mm. The maximum displacements at the tunnel
contour amount to approx. 33 mm (Fig. 21.35). A major portion of these displacements
already occurs at the temporary face.

The displacements of the shield skin amount to only a few mm, as already repre-
sented in Section 10.5.5 in a longitudinal section through the tunnel axis and in a
cross-section B-B approx. 12 m behind the temporary face (Fig. 10.32). The displace-
ments in cross-section B-B lead to stress resultants in a circumferential direction of
the shield which are plotted in Fig. 10.33. The calculated radial loading

σ r acting on
the shield ranges between approx. 0.9 MPa and 1.2 MPa and was already represented
in Fig. 10.31.