Material from the central borehole of the in-situ test was send to Helsinki for laboratory based impregnation with C14-PMMA. This gave a first indication of the porosities expected to be found during the in-situ impregnation (if estimates of stress release are accounted for).

The photomicrograph and corresponding autoradiography from the inlet hole are shown below.

Photomicrograph of a section of the core from the inlet hole of the in-situ test

Corresponding autoradiograph of the core from the inlet hole of the in-situ test

The digital autoradiographs found the measured porosities to be between 0.45 and 0.55 %, which is within the range observed at the GTS via other methods. This measurement was taken at a depth of around 80cm from the tunnel wall and well outside of any Excavation Disturbed Zone (EDZ). The next stage was to apply this methodology in situ.