Study on the Mechanical and Energy Evolution Characteristics of Oxidized Coal

To study the variation laws of the mechanical properties of coal with different oxidation degrees, coal samples were subjected to constant temperature oxidation at 80°C, 120°C, 160°C and 200°C by using a coal oxidation spontaneous combustion test system. Through a uniaxial compression experiment, the variation laws of mechanical parameters, failure characteristics and energy dissipation law of coals with different oxidation degrees were analyzed and obtained. The study shows that the stress – strain curves of coal with different oxidation degrees vary in different stages. The peak stress, elastic modulus, secant modulus and Poisson's ratio appear to decrease to different degrees with the deepening of oxidation, and the peak strain increases. The cracks on the surface of the coal samples increase and become more with the deepening of oxidation, the exothermic characteristics of the coal samples decrease, and the failure characteristics of the coal samples change from single shear-type failure characteristic to conjugate shear-type characteristic and then to shatter-type failure characteristic. With an increasing degree of oxidation, the total energy required for coal destruction gradually decreases, the conversion rate of total energy into elastic energy decreases, the dissipation energy gradually increases, and the release rate of elastic energy and the increase rate of dissipation energy gradually slow down after the peak strain.