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| Research on classification of rock tensile-shear fracture based on acoustic emission RA-AF values and kneedle algorithm |
| WANG Juxian1，LIANG Peng1，2，ZHANG Yanbo1，2，YAO Xulong1，2，YU Guangyuan1，2，GUO Bin1，3 |
(1. School of Mining Engineering，North China University of Science and Technology，Tangshan，Hebei 063210，China；
2. Mine Green Intelligent Mining Technology Innovation Center of Hebei Province，Tangshan，Hebei 063210，China；
3. Sijiaying Yanshan Iron Mine Co.，Ltd.，Hebei Iron and Steel Group，Tangshan，Hebei 063701，China) |
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Abstract The accurate determination of the boundary equation is crucial for the classification and identification of cracks in the rock fracture process using the acoustic emission RA-AF values. The granite shear acoustic emission monitoring experiment was carried out. Based on the crack classification method of acoustic emission RA-AF，the influence rule of slope k and intercept b of the boundary equation on the crack classification results was analyzed. With the help of kneedle algorithm of inflection point monitoring，a method to accurately determine the boundary equation was formed. Based on this，the results of crack classification were discussed and analyzed. The results indicate that both the slope k and the intercept b of the boundary equation have an impact on the crack classification results，and the influence depends on the size of the value of k and b. There exist critical slope ，and critical intercept . When the values are below the critical values，the classification results are greatly affected. While when they exceed the critical values，the impact on the classification results is small or almost negligible. The kneedle algorithm for inflection point detection can effectively determine the critical points of the boundary equation's slope and intercept，which provides a method and basis for accurately determining the critical slope and intercept in the boundary equation. Compared with the boundary equation without intercept，if the boundary equation has intercept b，the proportion of shear cracks will increase by about 20%. The research results provide a basis for determining the boundary equation of rock tensile-shear crack classification using acoustic emission RA and AF values，which is helpful to promote the application of this method in rock mechanics.
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