Tunneling in Swelling Rock - Rock Mechanics Based on an Anisotropic Jointed Rock Model - page 756

Figure 23.3 Calculation of the disturbed rock zone (Wittke 2012a)
Figure 23.4 Sealing structure
23.2.2 Anhydrite Surface underneath and in the Area of the Tunnel Invert
Where the anhydrite surface is located underneath the tunnel invert, swelling may arise
if the disturbed rock zone reaches below the tight zone at the anhydrite surface. Then
water from the water-bearing leached Gypsum Keuper can penetrate through the dis-
turbed rock zone into the unleached Gypsum Keuper causing swelling (Fig. 23.5).