Mechanical response and impact tendency index correction of gangue-coal combined structure

Abstract

To investigate the mechanical response during failure and the impact tendency characteristics of gangue-coal combined structure, uniaxial compression tests were conducted on nine groups of combined structures, each with varying gangue thicknesses and positions. The response patterns of compressive strength, elastic modulus, pre-peak accumulated energy, elastic energy index, and impact energy index were systematically analyzed. Furthermore, a new index for evaluating the impact tendency of gangue-containing coal was proposed, and its effectiveness was verified. The findings are as follows: (1) As the gangue thickness increases, both the compressive strength and the pre-peak energy of the combined structure decrease, whereas the elastic modulus increases accordingly. When the gangue is located in the lower-middle position, the combined structure exhibits the lowest compressive strength and elastic modulus but the highest pre-peak energy. (2) As the gangue shifts toward the middle position of the combined structure, the failure mode gradually transitions from complete “crushing” failure to an incomplete “point-type” failure. As gangue thickness further increases, the failure region evolves from overall failure to localized failure, with the degree of failure shifting from complete to incomplete. The K_crc value corresponding to “crushing” complete failure is higher and has a stronger impact tendency compared to “point-type” incomplete failure. (3) The proposed comprehensive impact instability evaluation index K_crc for the gangue-coal combined structure has shown a significant positive correlation with compressive strength (R_c) and impact energy index (K_E), further verifying its rationality in comprehensively assessing the impact tendency of gangue-containing coal bodies. Applying this index to the evaluation of gangue-containing coal seams provides a more accurate reflection of their impact tendency compared with the residual energy index, which has a wide range of potential applications and practical significance.

Keywords

gangue-coal combined structure / mechanical response / peak elastic energy density difference / impact tendency / comprehensive impact instability index

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