Experimental Study of Original Cracks Features Effecting on Fracture of Coal Samples under Uniaxial Compression

AbstractThe deformation and fracture process under load of coal-rock is the macro manifestation of the internal damage elements like the original crack, which is followed by further rupture, expansion, aggregation and interaction. And this damage appears in various dynamic disasters in coal mine, such as rock burst. Based on the methods such as photography, simplified projection and uniaxial compression system, the effect on original tiny crack distribution features of cylindrical coal sample, coal samples’ uniaxial compression strength, acoustic emission and electromagnetic radiation signals are studied. The test results indicates that: the tiny cracks on coal sample surface show three types like cracks that nearly parallel, about 45° inclination angle cracks, and large inclination angle cracks; the size of the original crack has significant impact on the uniaxial compressive strength of coal and signal characteristics of electromagnetic radiation, and the existence of obvious original cracks will significantly reduce the uniaxial compressive strength of coal, while the energy value of the electromagnetic radiation signals will enhance during uniaxial compression