Pressure-tunnel linings with deep rock grouting: Fid-Bau Portal

Pressure-tunnel linings with deep rock grouting

Éristov, V. S.

Conclusions Experience in the construction of the Roselan-Bati, Festenniog, Weinberg, Reisach, and Rama tunnels shows that the construction of pressure tunnels with a thin equalizing concrete lining and with deep strengthening grouting under a pressure equal to about twice the operating pressure in the tunnel in rocks diverse in their geologic and geotechnic characteristics is completely warranted both from the technical and, obviously, from the economic viewpoint. As a result of strengthening grouting of the rock the necessary compressive prestressing can be attained in the rock and in the lining, eliminating the occurrence of tensile stresses from the internal pressure and the opening of cracks.Observance of the following conditions is necessary:Conduction of preliminary, sufficiently extensive comprehensive investigations corresponding to the scale of the structure to determine the geologic structure of the rocks around the tunnel, its jointing, permeability, and deformation, strength, and other physical and mechanical properties;proper assignment of the number, direction, and depth of boreholes and of the necessary grouting pressure;selection of the compositions of the cement grouts corresponding to the geologic conditions and geotechnic characteristics of the rocks in each given zone;correct performance of injection work, use of simultaneous group injection over the entire perimeter of the lining over the greatest possible length with monitoring of the pressures and absorption of the grout;systematic instrument monitoring of the effect of grouting work by measuring deformations.