Squeezing Rock - Rock Mechanics Based on an Anisotropic Jointed Rock Model - page 109

Figure 4.17 Influence of discontinuities, viscoplastic displacements at the tunnel's contour
4.5.5 Influence of Supporting Pressure
Figure 4.18 shows the principal normal stresses and the extent of the plastic zone that
are calculated for case 4, in which discontinuities with reduced strength are assumed
and a supporting radial pressure of p r = 0.6 MPa is applied to the tunnel's contour
immediately after excavation (cf. Fig. 4.10 and Table 4.2). Compared with case 3 the
plastic zone decreases considerably.
The supporting pressure in case 4 leads to convergence of the viscoplastic displace-
ments at the tunnel's contour and thus to a stabilization of the tunnel (Fig. 4.19).