Effects of Excavation Damage on the Electrical Properties of Rock Mass

Electrical and Electromagnetic (EM) methods have been used for characterization of Excavation Damage Zone (EDZ) in conjunction with long-term safety evaluation of geological disposal of spent nuclear fuel. Physical properties of the rock have been tested in laboratory to characterise the property changes related to EDZ. EM research has focused around Ground Penetrating Radar (GPR) utilizing GPR EDZ method, developed for excavation quality control in means of EDZ extend. For 20 specimens, resistivity, relative dielectric permittivity (ε r ) as well as high frequency scattering parameters (electrical conductivity and ε r ) were measured. Induced Polarization (IP) values were calculated from resistivity data. Resistivity, IP and ε r , was produced to support the use of GPR image analysis and the GPR EDZ method. Results were analysed to reveal links between εr and conductivity, and to analyse possible depth dependencies. A positive association between electrical conductivity and ε r was observed. Changes in the electrical properties linked to shallow depths and visual EDZ features were observed, which seems to validate the theoretical basis of the GPR EDZ method. Electrical property data allows further modelling, development and assessment of the GPR EDZ method.