Correlated characteristics of crack box dimension and magnetic signals during coal failure

Crack is an important manifestation of the occurrence and development of coal failure under load, and magnetic signal is one of the ways of energy leakage of coal under load, and there must be a correlation between the two. In order to study the quantitative relationship between cracks and magnetic signals generated during the destruction of coal, and to further improve the theory of the monitoring and early warning technology of dynamic disasters used by magnetic signal in coal mine, firstly, RFPA2D numerical simulation software was used to simulate the crack morphology characteristics with different bedding properties and quantities of coal under static load. The reliability of the numerical simulation results was confirmed by comparing the experimental results in the laboratory. Secondly, combined with the established force-magnetic coupling model, the number of magnetic pulses and energy released after the failure of different samples were obtained. The relationship among bedding properties and magnetic pulse, magnetic energy, and the relationship among bedding quantity and magnetic pulse, magnetic energy were analyzed. Thirdly, the MATLAB software was used again to preprocess the cracked samples obtained from the simulation and calculate the crack box dimensions of the samples respectively. The correlation characteristics between the crack box dimension and the bedding properties and quantity were analyzed. Finally, the correlation characteristics between the crack box dimension and the number of magnetic pulses and magnetic energy after static load failure of the sample were comprehensively analyzed. The results show that the crack box dimension of sample without the bedding is the lowest, and for samples with horizontal bedding, the crack box dimension is linearly correlated with the number of bedding. There is no significant correlation between the crack box dimension and the bedding quantity for the sample with vertical bedding. For samples with horizontal bedding, the number of bedding has a positive relationship with magnetic pulses and magnetic energy. For samples with vertical bedding, the number of bedding has a negative relationship with magnetic energy, but not significantly related to the number of magnetic pulses. For the samples with horizontal bedding, the crack box dimension has a good positive linear correlation with the total number of magnetic pulses and total magnetic energy, while for the samples with vertical bedding, the crack box dimension has a good negative linear correlation with the total magnetic pulse number, but there is no correlation with the total magnetic energy.