Using AC Conductivity Measurements to Study the Influence of Mechanical Stress on the Strength of Geomaterials

Abstract

The Dielectric Spectroscopy technique is a tool that can be used to provide information regarding the physical and chemical properties of materials. In this work Dielectric Spectroscopy (DS) measurements were conducted on marble specimens that were previously subjected to uniaxial compressive stress up to fracture in order to investigate the influence of the mechanical stress on the dielectric properties of the specimens. Specifically, the ac conductivity (σac) was measured when an ac electric field in the frequency range 1 kHz - 1 MHz was applied upon dry and saturated specimens which were subjected successively to higher levels of mechanical stress. The experimental results indicate that there are systematic variations in the values of the ac conductivity after each stress application at a higher stress level. Such variations become more intense at higher stress values and can be used to indicate the upcoming fracture since significant increase of conductivity is recorded when microcracks formations appear and propagate in the sample bulk.