Investigation of the EDZ Using High-Resolution GPR with Modulating Frequency

The EDZ (Excavation Damage or Disturbed Zone) is considered to be a fast transport pathway and provides a boundary condition for transport in bentonite buffers in groundwater scenarios for the geological disposal of radioactive waste. The distribution of the EDZ obtained through in-situ measurements, is important for safety assessments. High-resolution Ground Penetrating Radar (HGPR) with modulating frequency functions as a wide-angle measurement technique. It is one of the advanced techniques that can be used to investigate the EDZ of a radioactive waste disposal tunnel. Verification tests of the HGPR were carried out using a model and in-situ condition in the gallery of Tono mine in central Japan, where comprehensive techniques for investigation, analysis and assessment of the deep geological environment had been developed. In summary, it is shown that the investigation technique was able to detect underground structures with a resolution of less than 0.1m.