ABSTRACT
The rock mass is typically a jointed aquifer where water moves through the most permeable discontinuities or through open channels along them. In general, the rock masses close to the surface are more jointed and the joints are more open than deeper in the rock mass. Visual observation carried out in many ungrouted tunnels indicates that most water leakage in general occurs in the part of the tunnel which is closest to the surface and is confined in fractures, faults and weathered zones (Nilsen and Thidemann, 1993 and Karlsrud, 2002).
