Once the injection of radioactive tracers was complete, a specialised epoxy resin containing a fluorescent dye was injected into the shear zone. The purpose of this stage is to stabilise the shear zone before the excavation stage. The techniques applied here were developed during the RMP in Phase IV (for details on Phase IV see History of the GTS in the Home section).

Before resin was injected, the hydraulic packers were removed from the test area and monitored by radiation protection. Resin injection packers were added in their place. Despite 3 years of contact with the high pH solution, most of the packers were unaffected. However, the extraction packer had developed a build up of white material around the extraction interval.

The packer systems were removed and monitored for contamination. The black sections are inflatable rubber sheaths which block the borehole, so allowing specific areas of the shear zone to be isolated from one another

The extraction packer developed a build up of white material (presumably secondary cement minerals) during 3 years circulation of high pH fluid.

Injection of resin into the shear zone is a complicated process. It requires accurate mixing of the resin components at the correct temperature for hardening of the resin. The resin must be warm enough to harden within the rock. If overheated, the hardening process may occur within the injection tubes or before the resin has fully saturated the test area. The machine used allows a very accurate control of the mixing ratios of the resin components. Once resin was injected in all boreholes, it was left to harden.

The two metal tanks contain the two components of the epoxy resin	Resin injection into the HPF shear zone. The blue tubes are part of the resin injection packers.
The resin injection team at the GTS (from left to right) Bernd Frieg (Nagra), Max Rüthi (PSI), Mario De Silva (Solexperts), Colin Biggin (Nagra), Karam Kontar (Solexperts) and Toni Bär (Nagra)

During this time, the remaining equipment was removed, monitored for radioactivity and decontaminated where necessary in preparation for the overcoring of the shear zone.

The packers systems were monitored for any contamination from the radionuclides. The uncontaminated packers could then be removed from the Controlled Zone

Toni Bär demonstrates his latest dance moves to celebrate the end of the resin injection stage

Continued in the overcoring section