Assessment of Rock Fracture Jacking During Grouting: Evaluation of an Analytical Solution Through Cases from Scandinavian Tunneling Projects-PPT Presentation

PPT Presentation

Pdf Summary

The presentation evaluates an analytical method for estimating rock-fracture jacking during grouting, using cases from the Haga Tunnel, part of Gothenburg’s West Link project in Sweden. The tunnel passes mainly through gneiss, with rock cover ranging from about 6 to 60 metres.<br /><br />The method links injection pressure and in-situ stress to fracture dilation and grout-spread distance. It uses deformation-limiting curves and estimates grout spread by relating injected grout volume to the volume associated with the fracture’s initial aperture and subsequent dilation. The presentation also highlights a trade-off: dilation can improve grout penetrability and spread, but may increase grout consumption and leave residual transmissivity.<br /><br />Two roof-fracture cases illustrate this contrast. In Case 1, with an initial aperture of 180 μm and in-situ stress of 23 bar, estimated dilation was 19 μm. The associated grout-volume increase was 1.5%, and residual transmissivity was negligible. In Case 2, a narrower fracture (minimum aperture 40 μm) under the same in-situ stress dilated by 67 μm. Its grout-volume increase was 30%, with residual transmissivity of approximately 3 × 10⁻⁹ m/s and residual dilation of 12 μm.<br /><br />Overall, the cases show that fracture response varies substantially with aperture and applied pressure. The analytical approach aims to support controlled deformation by balancing improved grout spread against increased grout use and the potential for residual conductivity.

Keywords

rock-fracture jacking

grouting

Haga Tunnel

West Link project

Gothenburg

analytical method

fracture dilation

grout spread

in-situ stress

residual transmissivity