Classification criteria for coal bursting liability based on portable Leeb hardness testing

Determining the bursting liability of coal is one of the main basis for evaluating the bursting risk degree of coal burst mine. Considering the complexity of existing classification procedures for determining coal bursting liability, a new method based on portable Leeb hardness testing is proposed. Combined with the Leeb hardness test, longitudinal wave velocity test and uniaxial compression experiment on 20 specimens from four coal mines, a fitting relationship between coal Leeb hardness and rock mechanics parameters was established. The energy evolution law during the compression failure process of specimens with different Leeb hardness values were investigated. A coefficient KPE was defined to describe the energy release rate during the failure of specimens, and the correlation between KPE and traditional indicators of coal bursting liability was analyzed. Based on the relationship between Leeb hardness and KPE, a coal bursting liability classification criteria based on Leeb hardness was established. To validate the rationality of this criterion, its classification results were compared with those based on the national standards and the ejection mass ratio of coal cuttingsF. Two engineering application scenarios from a strong coal burst mine in the Ordos Basin were selected to further assess the criterion's effectiveness in practical applications. The results show that the Leeb hardness of coal demonstrates a strong correlation with uniaxial compressive strength and elastic modulus, whereas there is no significant correlation with longitudinal wave velocity. The larger the Leeb hardnessis, the stronger the energy storage and energy release of the specimens in uniaxial compression tests.The KPE values varied significantly among specimens with different bursting liabilities and showed strong correlation with traditional bursting liability indicators, indicating that KPE can be effectively used for coal bursting liability classification. The KPE of specimens was positively correlated with Leeb hardness in a power function relationship, suggesting that as Leeb hardness increases, the bursting liability of specimens changes markedly. The coal bursting liability classification criteria based on portable Leeb hardness testing shows good consistency with national standards and the ejection mass ratio of coal cuttingsF classification results, and performs well in two engineering application scenarios, indicating that the method has a certain degree of feasibility and reliability.