Analysis of damage and failure characteristics of coal under uniaxial impact loading

Abstract

In order to investigate the damage characteristics and evolution of the coal body under uniaxial impact loading, a Split Hopkinson Pressure Bar （SHPB） device was used to obtain the kinetic response of the coal sample at an impact velocity of 5 m/s by adjusting the air pressure value of the storage chamber, and this was used as the main reference to determine the fine physical and mechanical parameter of the model. Using PFC3D software, numerical simulations of the damage process of coal bodies containing closed and unclosed straight fissures at different angles （0°, 30°, 60°, 90°） under uniaxial impact loading at 5 m/s impact velocity, and coal bodies without fissures at different impact velocity conditions were carried out. The influence of factors such as impact velocity and fracture distribution angle on the damage characteristics of coal bodies under uniaxial impact loading was investigated. The test results show that: when the impact velocity is low, the coal sample mainly follows the deformation damage criterion, and when the impact velocity increases to a certain degree, it mainly follows the strength damage criterion; fissures are usually generated by the four corners and the tip of the fissure and other media mutations, showing a “V” or “X” shaped trend of expansion, eventually showing an X-shaped damage zone; the inner and outer layers of coal samples show different failure forms, the inner layer is closer to the triaxial stress state than the outer layer, so shear failure is more likely to occur, while the outer layer is more likely to occur tensile failure. Overall, under uniaxial impact loading, the main form of damage to coal samples is tensile damage.

Keywords

• fissure-bearing coal bodies
• shpb uniaxial impact
• fracture type
• damage patterns
• particle flow