Experimental study of influence regularity of pyrite-bearing filling joints on mechanical properties of coal-rock

Abstract

The acoustic emission (AE) monitoring technique, scanning electron microscope (SEM) system and uniaxial compression test were carried out to study the effect of pyrite-bearing filling joints on the mechanical properties of coal samples. The results show that the pyrite-bearing filling joints have adverse effect on strength, elastic modulus and peak strain of coal samples. Compared with the relatively complete samples, the post peak failure was ductile of samples with pyrite-bearing filling joints, the stress-strain curve was ladder-shaped after the peak and the AE energy of each drop appeared a peak. Many inclined and slender filling joints on the coal surface had a significant effect on the mechanical properties of the samples. Under the action of axial compression stress, the internal cracks of coal-rock with pyrite-bearing filling joints had enough time to expand and connect, and induced failure of surrounding structures, thus reducing the strengths of the samples. When fine pyrite-bearing filling joints on the coal surface, the distribution of macro-cracks were less, and SEM image showed that the fracture surface was relatively flat. While many inclined and slender filling joints on the coal surface, the sample failure accompanied by more macro-cracks, and SEM image showed that there were more holes and cracks on the fracture surface.