Experimental Study on the Mechanical Stability and Mesoscopic Damage Characteristics of Coal Under Different Mining Disturbance Rates.

The mechanical behavior of the coal body acted upon by varying pressure is very important for the stability analysis of the actual mining face. Based on the designed stress loading path, uniaxial compression tests are performed on coal samples of different coal steps in the presence of various loading rates. The main goal of this investigation is to examine the internal damage and crack evolution characteristics of the coal samples. The results reveal that the ringing number and energy abruptly alter before the peak stress, the resistivity decreases, the damage increases and the internal fracture development of the coal rock intensifies. The low-order coal is essentially damaged in shear after several stages of loading, and the high-order coal is mainly damaged in tension due to the stress concentration caused by the primary cracks, and the fracture rapidly develops along the primary cracks. The obtained results of this study provide a theoretical basis for the design of the protective layer and the control of mining disturbances in the actual working face mining environment. Highlights: Development of an approach of mining disturbed stress loading rate. Assessment of mechanical properties of various coal rank samples subjected to mining disturbed stress environment. Loading rate variations cause sudden changes in the coal rock ringing number, energy, resistivity, and damage. Characteristics of fracture evolution of various coal rank samples during the loading process. [ABSTRACT FROM AUTHOR]