Time-frequency evolution law and generation mechanism of electromagnetic radiation in coal friction process

Yin, Shiping; Song, Dazhao; He, Xiaocong; Qiu, Liming; Wei, Menghan; Wang, Cunwen; Chen, Yang; Li, Pengpeng; Li, Jie

doi:10.1016/j.enggeo.2021.106377

Cited by 22 publications

(9 citation statements)

References 41 publications

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“…Various friction experiments showed that the sizes of broken asperities agreed with the FEMR estimates received during compression tests 32 , 37 . The results of coal studies showed that the FEMR signals are weak, and their energy is low at the stable sliding stage, while they are generated intermittently at the stick–slip stage 81 . Hence, the ongoing experiments can further provide a fresh perspective and add value to the general parameters and the individual pulse parameters, along with their connection with the crack dimensions, which correlate adequately from the theoretical point of view and as observed from the field data.…”

Section: Discussionmentioning

confidence: 99%

Insights into the Dead Sea Transform Activity through the study of fracture-induced electromagnetic radiation (FEMR) signals before the Syrian-Turkey earthquake (Mw-6.3) on 20.2.2023

Das,

Frid,

Rabinovitch

et al. 2024

Sci Rep

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Observations of fracture-induced electromagnetic radiation (FEMR) were conducted along the Dead Sea Transform (DST) from Sodom to Jericho, coinciding with a magnitude (Mw) 6.3 aftershock earthquake (EQ) in the Turkey-Syrian region on February 20, 2023. The FEMR parameters (“hits,” Benioff strain release, frequency, rise-time, energy) and associated crack dimensions were analyzed, focusing on trends leading up to the EQ. This study investigated the Benioff Strain plot and other parameters in three consecutive earthquake nucleation stages leading to the catastrophe. The first stage showed increased FEMR hits and frequency, decreased rise time (T′), and crack dimensions. In the second stage, FEMR hits and crack width decreased while other parameters continued to rise, accumulating the second-highest energy, likely due to high-stress drop. The third stage exhibited steadily increasing FEMR hits and energy and a notable increase in crack dimensions, suggesting an imminent macro failure event. The cyclic trend in FEMR hits indicates alternating periods of high activity and silence, potentially linked to stress changes during crack propagation. Taken shortly before the earthquake, these measurements offer valuable insights into how FEMR parameters vary before seismic events, bridging the gap between lab-scale studies of rock collapses under stress and large-scale failure phenomena.

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Section: Discussionmentioning

confidence: 99%

Insights into the Dead Sea Transform Activity through the study of fracture-induced electromagnetic radiation (FEMR) signals before the Syrian-Turkey earthquake (Mw-6.3) on 20.2.2023

Das,

Frid,

Rabinovitch

et al. 2024

Sci Rep

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“…According to formula (8), the relations between the amplitude of vector EMR (A s ) and crack sizes (D), distance from measuring points to the cracks (r), and crack azimuth angles (θ 0 ) are:…”

Section: Analysis Of Vector Effect Mechanism Of Emrmentioning

confidence: 99%

“…It extracts the eigenvalues for time-series monitoring and early warning of disasters without using the vector characteristics of EMR for space-time warning of disasters. It is primarily attributed to the fact that the mechanism of EMR was not clear in the early days and plenty of academics devoted their efforts to researching the mechanism of EMR [4][5][6][7][8].…”

Section: Introductionmentioning

confidence: 99%

Research on vector characteristics and applications of electromagnetic radiation induced by rock failure

Zhao¹,

He²,

Liu³

et al. 2023

Meas. Sci. Technol.

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Coal and rock electromagnetic radiation (EMR) measurement plays an essential role in the monitoring and early warning of underground engineering dynamic hazards as a real-time, dynamic, non-contact geophysical monitoring method of coal and rock fissure. The electromagnetic field has obvious directionality; however, the EMR measurement instruments used in underground engineering are scalar rather than vector instruments. Therefore, this paper uses a self-developed three-axis antenna to measure the vector EMR for rock Brazil splitting failure. Study the influence of crack size (D), the distance of measuring point (r) and crack azimuth angles (θ0) on the vector characteristics of EMR induced by rock splitting failure. Analyze the vector response mechanism of EMR induced by rock splitting failure, and conduct on-site vector EMR measurements in the Lilou Coal Mine. The study achievements are concluded as follows: the amplitude of vector EMR (As) increases linearly with the increase of crack size (D), decreases with the distance square (r2) from the measurement point to the crack increases, and increases and then decrease with the increase of angles (θ0) between the sample direction and the initial fixed position, showing arching changes; The direction of vector EMR (As) is mainly affected by θ0 impact. The results of experiments are consistent with that of theoretical analysis. The field measurement results show that the stress concentration area and its orientation of the roadway could be measured using the three-axis vector EMR instrument we researched and developed.

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“…Wei et al [38] studied the EMR of rock fracture and found that the dominant frequency decreases with the crack propagation at different stress levels. Yin et al [39] studied the time-frequency characteristics of EMR in the coal friction process and found that with increasing lateral pressure, the dominant frequency of EMR gradually increases. Lou et al [33] conducted a timefrequency analysis for EMR waveform induced by rock fracture using the improved EWT, the results show that the EMR is prone to have a high amplitude component of 70-100 kHz in the early stage after peak stress of rock sample, while 0-40 kHz in the later stage, and decays with a lower frequency component of 0-25 kHz.…”

Section: Introductionmentioning

confidence: 99%

Discrete characteristics of instantaneous frequency of EMR induced by coal and rock fracture

Lou

Jia

Wan

et al. 2023

Meas. Sci. Technol.

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To reveal the discrete characteristics of the instantaneous frequency of the electromagnetic radiation (EMR) waveform induced by coal and rock fracture, the uniaxial compression experiments for coal and rock samples were carried out, and the EMR signals with full waveform were acquainted and stored. The empirical wavelet transform (EWT) is used to filter and de-noise the EMR waveform, and then the short-time Fourier transform (STFT) is used to analyze the time-frequency characteristics of the waveform. The discrete characteristics of the instantaneous frequency with a larger amplitude and the relationship between the centroid frequencies and peak-to-peak values (Vpps) of the EMR waveforms are statistically analyzed. The results show that the centroid frequency of 0–100 kHz is negatively correlated with the Vpp, and the relationship between them shows a logarithm function relation. The instantaneous frequency of the EMR waveform of coal and rock fracture has significant discrete characteristics. In detail, for the rock sample, the instantaneous frequencies with relatively large amplitude are mainly 4.5 kHz, 19.5 kHz, 22.0 kHz, and 27.5 kHz; for the coal sample, the instantaneous frequencies are mainly 1.0 kHz, 4.5 kHz, 9.0 kHz, and 74.0 kHz. This discrete characteristic is determined by the natural properties and fracture characteristics of the sample. Compared with the homogeneous rock samples, the internal cracks of the coal samples are well developed and show strong anisotropy, resulting in the discrete characteristics of the instantaneous frequency being relatively weaker. The findings have certain guiding significance for optimizing the design of the EMR monitoring frequency band and improving the pertinence and accuracy of the monitoring and early warning for coal and rock dynamic disasters.

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Time-frequency evolution law and generation mechanism of electromagnetic radiation in coal friction process

Cited by 22 publications

References 41 publications

Insights into the Dead Sea Transform Activity through the study of fracture-induced electromagnetic radiation (FEMR) signals before the Syrian-Turkey earthquake (Mw-6.3) on 20.2.2023

Insights into the Dead Sea Transform Activity through the study of fracture-induced electromagnetic radiation (FEMR) signals before the Syrian-Turkey earthquake (Mw-6.3) on 20.2.2023

Research on vector characteristics and applications of electromagnetic radiation induced by rock failure

Discrete characteristics of instantaneous frequency of EMR induced by coal and rock fracture

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