Research on energy dissipation characteristics and coal burst tendency of fissured coal mass

Coal burst tendency is the natural property of whether coal rock mass can have coal burst, and the distribution of fissures has an important influence on it. In order to study the influence mechanism of the original coal fissures on the energy dissipation characteristics and coal burst tendency, the PFC^2D numerical simulation method was used to conduct uniaxial compression tests on coal specimens with different fracture types. The results show that: ①With the increase of the inclination angle of the fissure, the compressive strength and elastic modulus of the macroscopic mechanical parameters show a trend of decreasing first and then increasing; when the inclination angle of the fissure is 30, both of them reach the minimum value. The relationship between the macro-mechanical parameters of different fracture types is: non-coplanar parallel double-fissure specimen < single-fissure specimen < co-planar discontinuous double-fissure specimen.②The variation law of elastic strain energy and total strain energy is similar to that of macroscopic mechanical parameters. The parallel and non-coplanar fracture specimens form an energy dissipation structure between the fissures, and the coplanar discontinuous double-fissure specimen forms an energy concentration area between the fissures, revealing the intrinsic reason for the relationship between the elastic energy of different fracture types. ③The coal burst tendency is analyzed from the two perspectives of the ability of coal and rock to store elastic energy and the ability to release elastic energy after failure, and two coal burst tendency indicators, elastic energy storage rate and elastic energy release rate, are proposed. ④With the increase of the fissure inclination angle, both the elastic energy storage rate and the elastic energy release rate showed a trend of first decreasing and then increasing; when the fissure inclination angle was 30, the two coal burst propensity indexes both achieved the minimum value. The relationship between the coal burst tendency of different fracture types is: non-coplanar parallel double-fissure specimen < single-fissure specimen < co-planar discontinuous double-fissure specimen. The distribution of fissures has a significant coal burst on the coal burst tendency of coal mass, and the factor of fissures should be considered in the evaluation of the coal burst tendency of coal and rock mass and the prevention and control of rock burst.