关键词: 加载速率, 力学特性, 声发射, 力链演化, 破坏模式

Abstract: To study the effect of loading rate on the macro-mesoscopic fracture characteristics of uniaxial compression of coal, uniaxial compression tests of coal samples at three loading rates of 0.06, 0.3 and 3 mm/min were carried out. Combined with acoustic emission and numerical calculation methods, the influence of loading rate on mechanical properties, acoustic emission characteristics, crack propagation and macroscopic failure modes of coal samples were analyzed. The results show that the higher the loading rate, the greater the uniaxial compressive strength and peak strain of the coal; The accumulated ringing counts and acoustic emission localization events keep decreasing with increasing loading rate; the microscopic fracture damage transitions from tension damage to shear damage; the macroscopic damage mode changes from a small amount mixed tensile-shear microcrack damage at low loading rate to a single penetrating shear crack damage at high loading rate; the numerical simulation results effectively support the indoor test conclusions and reveal that the damage of coal samples is essentially the destabilization of the force chain system. It sees that the increase of axial stress before the peak stress makes the local force chain strength difference increase, and the fracture of the strong and weak force chains produces the macroscopic damage of the coal.

Key words: loading rate, mechanical properties, acoustic emission, force chain evolution, failure mode