Pressure stimulated currents in rocks and their correlation with mechanical properties

Abstract

Part of Special Issue "Precursory phenomena, seismic hazard evaluation and seismo-tectonic electromagnetic effects" Abstract. The spontaneous electrification of marble samples was studied while they were subjected to uniaxial stress. The Pressure Stimulated Current (PSC) technique was applied to measure the charge released from compressed Dionysos marble samples, while they were subjected to cyclic loading. The experimental results demonstrate that, in the linear elastic region of the sample, no PSC is recorded, while beyond the stress limit (s>0.60), observable variations appear, which increase considerably in the vicinity of sample failure, reaching a maximum value just before the failure. The emitted current is reduced on each loading cycle and it has a reciprocal dependence to the normalized Young modulus. The MCD model, applied out of the vicinity of sample failure explains successfully the above findings. The existence of a "memory-like" behavior of the sample, could justify the weakness or absence of electrical earthquake precursors, during an aftershock sequence.

Non-destructive evaluation of cement-based materials from pressure-stimulated electrical emission – Preliminary results

“…An intense PSC signal with repeated spikes is also detected under high constant uniaxial stress, associated with variations in strain rate [31,32]. This paper outlines experimental techniques to measure Pressure Stimulated Currents (PSC) on CBM, and compares the results with those obtained from rock materials [11,[16][17][18][19][20]. The PSC measurements are systematically recorded while the samples are subjected to temporally varying axial compressive stress, either with a short duration and high repetition rate, or at a low-rate stress increase up to fracture.…”

“…[21,22] From the very first experimental results it became evident that the characteristics of the electric signals indicate that the procedure of crack formation and development is accompanied by the creation of electric polarization [15,11]. On the other hand, the dominant relationship between stress variation rate, the electric charge released and the damage parameter when a sample is subjected to uniaxial compressive stress up to failure, was investigated [16,17]. After systematic measurements, a description of the pressure stimulated electric signals was attempted successfully using statistical mechanics methodology [23] while a linear correlation between the electric charge and the strain before the failure limit was ascertained.…”

“…Recent laboratory experiments taking recordings of electric signal emissions produced using various modes of uniaxial compressive stress upon rock samples, such as marble and amphibolites, have been analysed [15][16][17][18][19][20]. The electric signal is detected in the form of a weak electric current using a sensitive electrometer.…”

Measurement and correlation of acoustic emissions and pressure stimulated voltages in rock using an electric potential sensor

“…The generation mechanism/s is/are still uncertain but include the electrokinetic effect of moving water [6,7], piezoelectric effect of quartz [6,8], rock fracture (contact and separation of fresh surfaces) [9], and moving charge dislocations [10,11]. Some of these studies have shown that pressure stimulated current (PSC) emissions are related to a change in Young's modulus [12] and variations in PSC are observed beyond the linear elastic limit in marble specimens [13]. PSCs are also associated with high amplitude acoustic emissions (AE) events and high event rates in cement mortar beams [14].…”

The results of experimental studies of VLF–ULF electromagnetic emission by rock samples due to mechanical action

“…Different mechanoelectrical transformations can occur during initiation processes. Laboratory experiments show that rocks, even those that do not contain piezoelectric minerals, can generate EM emissions in a wide frequency range under mechanical stress, as well as pressurestimulated currents (Anastasiadis et al, 2007;Rabinovitch et al, 1998;Stavrakas et al, 2004;Freund, 2007;Triantis et al, 2007;Yasuhiko et al, 2009). We need to mention that, usually, published papers represent the results of experiments carried out with only one type of mechanical influence like loading, with the subsequent fracture of the samples or gradual loading without failure; impact; rubbing samples with, as a rule, smoothed surfaces.…”