The influencing factors and mechanisms of the electromagnetic radiation during rock fracture

Abstract

Based on the laboratory experiments this paper presented that the primary influence factors about the electromagnetic radiation during rock fracture are the rock mechanics characters and mineral components. The brittle samples and samples contained quartz, pyrite, chalopyrite produce electromagnetic radiation easily. There are three fracture-radiation effects. The crystal fracture effect produces the high frequency electromagnetic signals, the piezoelectric effect produces low frequency signals and the natural semiconductor effect produces middle frequency signals possessed distinct wave-shapes.Key words: electromagnetic radiation rock fracture fracture-radiation effect crystal fracture effect piezoelectric effect natural semiconductor effect Experiment method and resultsThe samples are cut into cube approximately, about 30~100 cm s, and are pressed with a single axial force at uniform pressing rate. The eleetromagnetie radiation signals are recorded durhag all process pressing a sample to fracture. The sensors consist of two magnetic core antennas, a ring coil and a microphone, which respectively receive the high, middle, low frequency signals and sound signals. All the signals are amplified and recorded by a high-speed acqusition/analysis * .ACTA SEISMOLOGICA SINICA Vol. 10 system of data (DAS-820). For high, middle frequency signals, the sampling freqency are 10 MHz, the sampling length 100 kB. For low frequency signals and sound signals, the sampling frequency are 100 kHz, sampling length 70 kB. The signals are caught by inter-trigger way and trigger level is set above three times of the worksite noise level. Negative delay time 1~10 kB is set for recording the noise background. After processing the large number of acquired data, the electromagnetic radiation signals and corresponding sound signals are distinguished by the computer.The primary experiment results state that the electromagnetic radiation may be classified the high (1~5 MHz), middle (0. 1~1 MHz) and low (0. 1~100 kHz) frequency signals (For convenience the following is abbreviated to the HEMS, MEMS and LEMS respeetivly). Because it is limit by sampling frequency, the signals above 5 MHz can not be resolved. Not all kinds of rocks can produce signals during fracture. The HEMS, MEMS and LEMS appear not always at the same time. The strong signals appear while the main fracture happen. Before or after it, the weak signals appear. The time domain characters of the three kinds of signals distribution are random and earl be divided into many segments. The wave-shape characters of HEMS are vibratory pulse showers and of the LEMS are similar to non-regular sine attenuation vibration. The samples contained quartz, pyrite or ehalopyrite earl produce MEMS, whose distinct wave-shape include two kinds of haekly pules showers : sine attenuation vibration, and being similar to square waves. A detailed discussion about experiment methods, results and signal characters is published in another paper (Liu, et al. ,1997 ).

Changes in Frequency of Electromagnetic Radiation from Loaded Coal Rock

“…Guo and Liu (1995) established an electric quadrupole model, calculated the frequency of the near electromagnetic field, and found that the frequency of the near electromagnetic field was related to the size of coal samples and the length of initial cracks and was about 50 kHz-1 MHz for granite samples with typical sizes and lengths of initial cracks. Liu et al (1997) experimentally found that rock during its rupture could produce EM signals of high frequency (1-5 MHz), intermediate frequency (100 kHz-1 MHz), and low frequency (100 Hz-100 kHz).…”

Dehydrogenating properties of supported low-percentage palladium-containing catalysts

“…(13), the solutions we derive include the ones given in Refs. [1] ∼ [5], while when b i = 0, ours are all new solutions. In this sense we have extended the results obtained by Refs.…”

“…In this sense we have extended the results obtained by Refs. [1] ∼ [5]. Hence we are able to solve more nonlinear evolution equations and find more new solutions of the corresponding nonlinear evolution equations.…”

“…[1] ∼ [5]. After that some effort has been made to improve and extend the above method and apply it to solving many nonlinear evolution equations.…”

Experimental Study on Precursor Laws of Microwave Radiation from Loaded Coal During its Deformation and Fracture

“…During coal and rock's deformation and failure, the dielectric constant increases and the emissivity decreases, thus leading to dropping MWR and its brightness temperature [25] . Moreover, the intensity of EMR generated by coal bursts will be changed if it meets natural semiconductor minerals, such as a majority of metal sulfides, so-called natural semiconductor property [26] . In the piezoelectric field, because there are natural similar semiconductor heterostructure to p-n-p or n-p-n junctions, as well as other heteromorphical conversion lock-off layers in some coal rock minerals, "active components", similar to transistor and silicon-controlled rectifiers and related to electrical circuits, are formed near their barriers.…”