Influence of Borehole Number on Coal Rock Mass Strength and Acoustic Emission Characteristics

In this paper, considering the number of different boreholes and using the parallel bond model in particle flow program PFC^2D, the mechanical characteristics and acoustic emission evolution laws of coal rock were studied systematically under the condition of different drilling numbers. The results show that: with the increase of the number of boreholes, the peak strength, peak strain, elastic modulus and the time required to reach the peak point of the coal rock mass decrease gradually, and the extent of the reduction gradually decreases; with the emergence of boreholes, the acoustic emission characteristics of coal rock mass change as follows: in elastic stage, acoustic emission characteristics are no longer stable with large or small fluctuations; in the plastic flow stage, acoustic emission characteristics exhibit multiple peaks, and in the residual stage, acoustic emission exhibits unstable decrease characteristics; under the condition of different number of boreholes, the damage modes of coal rock mass and deformation of holes are different.