Time-Frequency Characteristics and the Influence Mechanism of the EMR from Coal with Different Joint Angles
Open Access
- 24 September 2021
- journal article
- research article
- Published by Hindawi Limited in Shock and Vibration
- Vol. 2021, 1-17
- https://doi.org/10.1155/2021/8340076
Abstract
It is vital to understand the electromagnetic radiations time-frequency characteristics in the process of coal and rock failure with different joint angles in order to reveal the generation mechanism of the electromagnetic radiation (EMR) and improve the accuracy of EMR early warning. We studied the time-frequency characteristics of EMR signals of coal samples with different joint angles. The study finds that, (1) with the increase of joint angle, the failure time and peak load of samples decrease first and increase later, and the postpeak failure time decreases gradually. The EMR counts peak value showed a slow rise, a sharp rise, and a slow rise in the three intervals of α=0° to 45°, 45° to 60°, and 60° to 90°, respectively. The accumulated EMR counts showed a steady upward trend. The duration of the EMR waveform, the dominant frequency of the EMR, and the peak number of the frequency spectrum of coal samples are on the rise. (2) As the joint angle increases, the samples failure mode changes from the stage fracture dominated by tension cracks to the rapid fracture with the coexistence of shear and tension cracks and finally to the burst fracture which produces a large number of fragments. This is also the main reason for the difference of the EMR generation mechanism and the signal of samples with different joint angles. (3) According to the experimental results, we established the modified formulas for calculating the EMR threshold value and deviation of coal and rock with joints under different stress environments and revealed that the longer the EMR waveform duration, the higher the dominant frequency, and the more the number of spectrum peaks, the greater the burst risk of coal and rock.Keywords
This publication has 40 references indexed in Scilit:
- Numerical simulation of acoustic emission in brittle rocks by two-dimensional finite-discrete element analysisGeophysical Journal International, 2013
- Natural electromagnetic radiation (EMR) and its application in structural geology and neotectonicsJournal of the Geological Society of India, 2010
- Long-wavelength P-wave and S-wave propagation in jointed rock massesGeophysics, 2009
- Electromagnetic radiation induced by mining rock failureInternational Journal of Coal Geology, 2005
- Electromagnetic Radiation from Rock During Uniaxial Compression Testing: The Effects of Rock Characteristics and Test ConditionsRock Mechanics and Rock Engineering, 2005
- Estimation of rock mass deformation modulus and strength of jointed hard rock masses using the GSI systemInternational Journal of Rock Mechanics and Mining Sciences, 2003
- Anisotropic strength and deformational behavior of Himalayan schistsInternational Journal of Rock Mechanics and Mining Sciences, 2003
- Effect of joint sets on the strength and deformation of rock mass modelsInternational Journal of Rock Mechanics and Mining Sciences, 1998
- Rockburst hazard forecast by electromagnetic radiation excited by rock fractureRock Mechanics and Rock Engineering, 1997
- Experimental study of the features of VLF, MF, HF and VHF electromagnetic radiation accompanying rock fractureActa Seismologica Sinica, 1996