Research on the Failure Evolution Process of Rock Mass Base on the Acoustic Emission Parameters

Abstract

Fracture mechanics behavior and acoustic emission (AE) characteristics of fractured rock mass are related to underground engineering safety construction, disaster prediction, and early warning. In this study, the failure evolution characteristics of intact and fracture (e.g., single fracture, parallel fractures, cross fractures, and mixed fractures) coal were studied and contrasted with each other on the basis of the distribution of max amplitude of AE. The study revealed some meaningful results, where the value of b (i.e., the distribution characteristic of max amplitude of AE) could represent the failure evolution process of intact and fractured coal. The maximum amplitude distribution of AE events was characterized by Gaussian normal distribution, and the probability of the maximum amplitude of AE events corresponding to 35∼50 dB was the largest. In the stress range of 60∼80%, AE events and maximum amplitude increased rapidly, and the corresponding b value decreased. The energy of AE events showed a downward trend after reaching the maximum value at about 80% stress level. Under the same stress level, the more complex the fracture was, the larger the b value of coal–rock mass was, and the stronger the inhibition effect on the fracture expansion caused by the internal fracture distribution was. Due to the anisotropy of coal–rock mass with a single crack, the distribution of the b value was more discrete, while the anisotropy of coal–rock mass with mixed crack decreased, and the dispersion of the b value decreased. The deformation of cracked coal mainly caused by the adjustment of cracks during the initial loading b value experienced a trend of decreasing first, then increasing, and then decreasing in the loading process. When the load reached 0.8 times of the peak strength, the b value had a secondary decreasing trend, indicating the macroscopic failure of the sample, which could be used as a precursor criterion for the complete failure of coal–rock mass.

Experimental study on failure precursors of coal and sandstone based on two‐step clustering of acoustic emission characteristics

“…More recently, Liu et al represented the evolution of coal failure by the value of b over a stress range of approximately 60%–80%, such that the number and maximum amplitude of AE signals increased rapidly as the corresponding b ‐value decreased. They found that the energy of AE signals exhibited a declining trend after being maximized at a stress level of approximately 80% 21 …”

“…They found that the energy of AE signals exhibited a declining trend after being maximized at a stress level of approximately 80%. 21 In terms of the study on AE precursors of coal and rock failures. Zhang et al considered the precursory AE characteristics of coal and rock failure by studying the characteristics of the energy, dominant frequency, and amplitude of AE signals in the process of granite failure under uniaxial compression.…”

Experimental study on strength and failure characteristics of mortar specimens with prefabricated cracks under uniaxial and triaxial stress

“…Worley et al (2019) demonstrated the effectiveness of AE technology when detecting cracks. Liu et al (2021) studied the failure evolution process of intact rock and fractured rock mass specimens under uniaxial loading condition on the basis of the maximum amplitude distribution of AE events. Wang et al (2022) examined the mechanical properties and fracture propagation characteristics of the fractured rock mass under coupling of heavy rainfall infiltration and mining unloading by using of PFC numerical software.…”