Experimental Investigation on Time-Frequency Characteristics of Microseismic Signals in the Damage Evolution Process of Coal and Rock

Abstract

The deformation and failure of coal and rock materials is the primary cause of many engineering disasters. How to accurately and effectively monitor and forecast the damage evolution process of coal and rock mass, and form a set of prediction methods and prediction indicators is an urgent engineering problems to be solved in the field of rock mechanics and engineering. As a form of energy dissipation in the deformation process of coal and rock, microseismic (MS) can indirectly reflect the damage of coal and rock. In order to analyze the relationship between the damage degree of coal and rock and time-frequency characteristics of MS, the deformation and fracture process of coal and rock materials under different loading modes was tested. The time-frequency characteristics and generation mechanism of MS were analyzed under different loading stages. Meanwhile, the influences of properties of coal and rock materials on MS signals were studied. Results show that there is an evident mode cutoff point between high-frequency and low-frequency MS signals. The properties of coal and rock, such as the development degree of the original fracture, particle size and dense degree have a decisive influence on the amplitude, frequency, energy and other characteristic parameters of MS signals. The change of MS parameters is closely related to material damage, but has no strong relation with the loading rate. The richness of MS signals before the main fracture depends on the homogeneity of materials. With the increase of damage, the energy release rate increases, which can lead to the widening of MS signals spectrum. The stiffness and natural frequency of specimens decreases correspondingly. Meanwhile, the main reason that the dominant frequency of MS detected by sensors installed on the surface of coal and rock materials is mainly low-frequency is friction loss and the resonance effect. In addition, the spectrum and energy evolution of MS can be used as a characterization method of the damage degree of coal and rock materials. Furthermore, the results can provide important reference for prediction and early warning of some rock engineering disasters.

Experimental investigation on time‐frequency evolution characteristics of electromagnetic radiation below ULF reflecting the damage performance of coal or rock materials

“…where k = 1, 2, 3, …, n À 1, argmin is defined as the global minimum. Yang et al 43 modified the above method based on whether there was a local minimum before the global minimum and believed that if there was local minimum, the first minimum would be taken as the cut-off point. If the local minimum did not exist, the global minimum point was used as the cut-off point.…”

“…However, frequency domain analysis can screen out the real EMR signals and play a vital role in improving the accuracy of EMR prediction. Most researchers use Fourier analysis, wavelet analysis, and empirical mode decomposition (EMD) methods to reduce noise and achieve good results 31,39,43 . The EMR induced from deformation and fracture of coal and rock is broadband, and many researchers have found that the frequency of EMR ranges from DC/ULF to VHF (or even higher) through studies on different coal and rock materials in different observation scales 44,45 .…”

“…Most researchers use Fourier analysis, wavelet analysis, and empirical mode decomposition (EMD) methods to reduce noise and achieve good results. 31,39,43 The EMR induced from deformation and fracture of coal and rock is broadband, and many researchers have found that the frequency of EMR ranges from DC/ULF to VHF (or even higher) through studies on different coal and rock materials in different observation scales. 44,45 Moreover, the dominant frequency of EMR in the deformation and fracture of coal and rock is variable, which is closely related to the stress stage of coal and rock.…”

Study on the Impact Failure Rules of Roadway Floor Induced by Dynamic Load Disturbance under Extremely Thick Conglomerate

“…Coal is an indispensable conventional energy in many countries and regions. Ensuring safe mining and efficient operation of coal mines has always been the long-term goal of the coal industry. , The complex geological environment and tectonic movement of the coal seam determine that the underground coal seam mining process will face potential risks such as water inrush, rockburst, gas outburst, and coal dust explosion. , In China, coal consumption still constitutes 65% of total primary energy consumption . In recent years, there has been a notable escalation in the depth and intensity of coal mining operations, further elevating the likelihood of mine disasters such as rockbursts …”

Experimental study on the evolutionary characteristics of acoustic signals produced by granite damage under uniaxial compression

“…In terms of AE signals, AE counts (Kong et al., 2019), AE energy (Tian et al., 2021), and AE entropy (Yang et al., 2021) were used to obtain damage curves for rock specimens during loading, and their damage variables showed a very consistent trend. In terms of MS signals, a damage equation was established by using MS events in coal rock damage evolution (Yang et al., 2020). However, in terms of sound signals, the evaluation of rock damage progression has rarely been reported in the literature.…”