Damage and fracture law of outburst coal bodies in tectonic zones under impact disturbances

Abstract

The geological tectonic zone is closely related to outburst. Taking the outburst coal bodies in tectonic zones as the research object, combined with DIC and AE monitoring technologies and discrete element simulation, the mechanical response, crack evolution and energy characteristics of coal bodies under different loading rates (impact disturbances) were studied. The results show that both the uniaxial compressive strength and elastic modulus are positively correlated with the loading rate, with a maximum increase in compressive strength of 25.15 %. The uniaxial compressive strength is more sensitive to impact disturbances. The failure modes of coal bodies can be divided into the “slip-crack synchronization (S & C) type” and the “crack-first-then-slip (C & S) type”. The slip in tectonic zones is more severe at high loading rates. At low loading rates, shear cracks dominate (60.01 %), while the proportion of tensile cracks increases significantly (70.52 %) at high loading rates. Additionally, the rate of axial crack growth decreases as the loading rate increases. The peak values of total energy and dissipated energy increase significantly with the loading rate, and the peak energy of the C & S type is greater than that of the S & C type. Energy is preferentially released through the slip of tectonic zones and the propagation of radial cracks.