Numerical Simulation Study on Mechanical and Acoustic Emission Characteristics of Coal-Rock Combined Body Subjected to Cyclic Disturbing Loading

In order to further study the mechanical properties of coal-rock combined body, the conventional uniaxial compression and cyclic disturbing loading tests were carried on it by numerical simulation method. The main conclusions are as follows: Under the same rock proportion, the strength and elastic modulus of sandstone-coal-sandstone (SCS) combined body in conventional uniaxial compression test are greater than that of mudstone-coal-mudstone (MCM) combined body; and their strength and elastic modulus increase exponentially with the increase of rock proportion. In the conventional uniaxial compression and cyclic disturbing loading tests, with the increase of rock proportion, the difference of stress-strain curve shape of SCS and MCM combined bodies increases, and the peak axial strain of SCS and MCM combined bodies shows the evolution characteristics of "first decreasing and then increasing". Under the same rock proportion, the strength of SCS combined body in cyclic disturbing loading test is greater than that of MCM combined body; and their strength increases exponentially with the increase of rock proportion. The cyclic disturbing loading has two effects on the combined bodies, namely: plastic softening and plastic strengthening effects. The mutual restriction and competition of these two effects will determine the strength of combined body. Under the same rock proportion, the maximum AE hit count of MCM combined body is greater than that of SCS combined body, and the maximum AE hit count of SCS and MCM combined bodies presents the characteristics of "big at both ends and small in the middle" with the increase of rock proportion.