Abstract
When an underground rock is deformed or fractured by an external or internal force, the energy will be released in the form of an elastic wave, which is known as the acoustic emission (AE) phenomenon. Extracting useful information from complex AE signals for the early warning of fracture characteristics and the damage monitoring of rock materials is of great significance for the prevention and control of dynamic disasters in coal mines. In this work, by taking rod-shaped rocks and plate-shaped rocks with different lithologies as the research objects, the elastic wave propagation characteristics of the rod-shaped rocks and plate-shaped rocks were studied by a self-constructed experimental platform. The results demonstrate that the elastic wave attenuation of the rod-shaped marble was the fastest, and the elastic wave attenuation characteristics of the three groups of rod-shaped granite were similar. The attenuation of the P-wave preceded that of the S-wave. With the increase in the propagation distance, the amplitude of the large-scale plate-shaped rock showed an approximate exponential attenuation characteristic. The elastic wave attenuation of the plate-shaped granite in the 0° direction was stronger than that of the plate-shaped marble, and it was weaker than that of the plate-shaped marble in the 45° and 90° directions. The energy changes in marble were more severe than those in granite. The main dominant energy of the AE signals of experimental rock was concentrated in the range of 0–176.78 kHz, and part of the residual energy was located in the high-frequency band of 282.25–352.56 kHz.
Highlights
Coal resource is an important strategic resource [1,2,3]
Before the excavation of underground rock mass in coal mines, the original rock stress is in an equilibrium state. e original state of stress balance is destroyed because of the influence of mining activities, resulting in the redistribution of the rock stress and causing fracture damage to the rock mass [4,5,6,7]. e changes in the stress state and internal structure often lead to the instability and fracturing of the rock mass, resulting in rockbursts, mine earthquakes, and other coal rock dynamic disasters [8,9,10,11,12,13]. e process of instability and fracturing of the rock mass is the process of initiation, propagation, and aggregation of internal microcracks, resulting in the formation of macrocracks and the loss of bearing capacity
In the 45° direction, the marble exhibited the enhancement of energy value after 55 cm. It is the reflection of the acoustic emission (AE) wave along the 45° direction when it met the boundary, and the wave enhancement phenomenon was formed by the superposition of multiple reflections and refractions. e marble and granite showed the same trend in the 90° direction
Summary
Coal resource is an important strategic resource [1,2,3]. Before the excavation of underground rock mass in coal mines, the original rock stress is in an equilibrium state. e original state of stress balance is destroyed because of the influence of mining activities, resulting in the redistribution of the rock stress and causing fracture damage to the rock mass [4,5,6,7]. e changes in the stress state and internal structure often lead to the instability and fracturing of the rock mass, resulting in rockbursts, mine earthquakes, and other coal rock dynamic disasters [8,9,10,11,12,13]. e process of instability and fracturing of the rock mass is the process of initiation, propagation, and aggregation of internal microcracks, resulting in the formation of macrocracks and the loss of bearing capacity. E changes in the stress state and internal structure often lead to the instability and fracturing of the rock mass, resulting in rockbursts, mine earthquakes, and other coal rock dynamic disasters [8,9,10,11,12,13]. Few analyses have compared and studied the similarities and differences of the elastic wave propagation characteristics in different rock materials by comprehensively using the methods of signal analysis and wavelet packet waveform analysis. In these analyses, the AE signal waveform is analyzed, and the time-frequency characteristics of the AE signal waveform received by different position sensors were extracted. Rough this research, certain research methods are presented, and a theoretical basis for the study of wave propagation law in complex three-dimensional rock is provided
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