Squeezing Rock - Rock Mechanics Based on an Anisotropic Jointed Rock Model - page 107

Figure 4.15 shows the viscoplastic displacements at the tunnel's contour that are calcu-
lated for cases 1 and 2. At 300 days after excavation, the calculated displacements are
considerably larger in case 2 compared with case 1. However, in both cases, convergence
of displacements is achieved. Thus, the tunnel can be considered as stable without a
support under the assumptions that have been made for cases 1 and 2.
Figure 4.15 Influence of residual strength, viscoplastic displacements at the tunnel's contour
4.5.4 Influence of Discontinuities
Figure 4.16 shows the principal normal stresses and the extent of the plastic zone at
300 days after excavation that are calculated for case 3. Comparison of Figs. 4.12, 4.14
and 4.16 clearly indicates a considerable increase of the plastic zone compared with cases
1 and 2 if discontinuities with reduced strength (Fig. 4.10) are accounted for.