Electromagnetic phenomena associated with rock deformation have been detected using various electrical measurement methods. Studies demonstrate that this includes electric field. A recent approach to this is enabled through a new, low cost sensor technology, the Electric Potential (EP) Sensor. The EP Sensor has previously measured complementary electric field signals extant with stress-induced currents in marble and granite. This paper presents preliminary research, measuring stress-induced electric field changes in uniaxial compressive stress tests on sandstone and granite until failure. The result is a unique data-set that reveals stress-induced electric field, which increases in amplitude and frequency simultaneously, up to the point of failure. It is seen that the electric field is sensitive to two factors controlled in these tests, specifically lithology and drying condition (moisture content). The findings are important since they provide information regarding stress state and fracture processes occurring. This technology has potential for application to rock at the field-scale.
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