Study on the Coupling Model of Electromagnetic Radiation and Axial Strain for Coal-Rock Mass Failure Under Load

To conduct an in-depth study of the pre-fracture process of composite coal-rock bodies under varying loading rates and coal content, the axial strain characteristics and electromagnetic radiation (EMR) theory related to the fracture were analyzed. An EMR -axial strain coupling model was derived and established, and this was analyzed and verified through uniaxial loading experiments. The experiments used composite coal-rock samples with three different coal ratios (1:1:1, 1:2:1, 1:4:1) and tested them under three loading rates of 0.3, 0.4, 0.5 mm/min, focusing on the response patterns of axial strain and EMR. The results indicate that the established EMR-axial strain model has high accuracy, the EMR intensity has high sensitivity to the change of axial strain, and the two have a strong correlation. Through the collection and analysis of data, it can be used as the basis for describing the first three stages of the fracture process of loaded coal-rock mass. The increase in coal proportion of composite coal-rock mass causes changes in axial strain, leading to a continuous increase in EMR amplitude variation in each stage. However, the overall EMR intensity increases slowly first and then rapidly with the increase of axial strain, which proves the correctness of the established coupling model. Under different loading rate conditions, an increase in the loading rate will significantly increase the strain rate, leading to an enhancement in the amplitude of EMR. However, the relationship between the change in axial strain and the intensity of EMR exhibits a cubic nonlinear relationship, which satisfies the established coupling model. This study not only reveals how the coal proportion and loading rate influence the evolution pattern of EMR and axial strain, but also provides a crucial theoretical basis and technical support for identifying precursors to coal-rock instability and issuing early warnings for rock bursts through the established coupling model.