Effects of dynamic velocity on the dynamic compressive mechanical properties and energy evolution of coal specimens

Abstract

ABSTRACT Dynamic compressive parameters of coal specimens were driven not only by impact velocities, but also by preloaded confining pressure, and impact loading methods. This paper investigates the influences of dynamic parameters based on the split Hopkinson pressure bar (SHPB) experimental data obtained from the dynamic compressive impact tests on 12 coal specimens under four different impact velocity. The analysis of the experimental results confirmed that with an increase of dynamic velocity, and then the dynamic compressive strength is constantly increases. When the dynamic velocity is 8.10 m/s, and then reacheed the maximum dynamic strength of 25.11 MPa of the coal specimen. Furthermore, the dynamic velocity of 8.10 m/s was defined as the threshold value of the dynamic strength increased. The greater of dynamic velocity, the higher degree of fragmentation of the coal specimens. The transmitted energy, reflected energy, and absorbed energy of coal specimens shows a directly proportional relationship with the incident energy. The results highlight the first and second dynamic deformation moduli can clearly explained the deformation laws of elastic and plastic stages of the coal specimens. It is also found that the maximum of strain rate is 177.28 s−1 and the maximum ultimate strain is 2.47 × 10−2of the coal specimens. The research results were beneficial to supplement the coal-rock dynamics theory, thus also providing a direction for safety and effective mining and crushing in coal mines.