Squeezing Rock - Rock Mechanics Based on an Anisotropic Jointed Rock Model - page 98

sure may not be admissible for the lining even though the rock mass may remain elastic.
If the same stiff lining is installed after a certain radial displacement has taken place a
considerably smaller supporting pressure p r, re d is sufficient to stabilize the tunnel (Figs.
4.3 and 4.9). The radial displacement at equilibrium, however, may exceed the elastic
limit so that the rock mass does not behave elastic anymore and a plastic zone is formed
(Fig. 4.8).
Figure 4.8 Convergence-confinement method, simplifying assumptions
Figure 4.9 Convergence-confinement method, ground reaction curve and support reaction curves