TBM Tunneling - Rock Mechanics Based on an Anisotropic Jointed Rock Model - page 695

This comprises the installation of the shield and the segmental lining as described in
Section 10.5.2. As support, the segmental lining and the shield, including the stiffenings,
were considered. Simultaneously, the slurry pressure is applied to the temporary face
and the water pressure is applied to both the shield and the segmental lining. Uplift and
seepage forces calculated by the seepage flow analysis were introduced as volume forces.
The support consisting of the shield and the segmental lining is installed into the FE-
mesh which has deformed according to the primary state. The support therefore initially
experiences too high a loading due to excavation and the displacements in the second
computation step are underestimated. Therefore in computation steps 3 to 17 a head-
ing of 1 m each is simulated according to the step-by-step method (Fig. 21.32, lower,
Section 10.5.2).
21.3.5 Analysis Results
Figure 21.33 shows the results of the seepage flow analysis. In the area of the temporary
face and of the shield, high hydraulic gradients i arise, which lead to high seepage forces.
As a consequence, in case A, very high displacements take place at the temporary face
which are directed towards the tunnel and do not converge in the course of the visco-
plastic iterative analysis (Fig. 21.34, Section 10.5).
Figure 21.33 Piezometric heads and hydraulic gradients (Wittke et al. 2006)