TBM Tunneling - Rock Mechanics Based on an Anisotropic Jointed Rock Model - page 701

Figure 21.39 Normal and shear stresses in sections, computation step 3, longitudinal section
(plane x = 0)
Figure 21.41 shows the calculated viscoplastic strains in the x direction and the z di-
rection, in cross-section 1-1 (Fig. 21.38). These are decisive for the amount of rock
mass loosening and permeability changes due to excavation. The interpretation of these
strains with respect to permeability changes is based on an in-situ permeability of the
undisturbed rock mass of 10 -9 m/s (cf. Table 8.1). From viscoplastic strains, aperture
changes, and thus permeability changes, of the horizontal, bedding-parallel disconti-
nuities and vertical joints (Fig. 8.1) were back calculated assuming a mean spacing of
these discontinuities of 5 cm and 1 m, respectively.