Investigation of kinetic energy dissipation characteristics of the drill string during rotary drilling in underground coal mines

In underground coal mine rotary drilling, rock-breaking energy is transmitted from the drill string to the drill bit. Nonlinear vibrations of the drill string within the borehole result in kinetic energy dissipation. To address this issue, a kinetic energy dissipation model of the drill string incorporating surrounding rock properties was established, and the dissipation characteristics were systematically investigated. The results indicate that when the drill string intrudes into the borehole wall rock, the drill string mass and wall thickness are positively correlated with kinetic energy dissipation, whereas the internal friction angle shows a negative correlation. Poisson’s ratio and density exert only marginal influence on drill string kinetic energy dissipation compared with strength- and stiffness-related parameters. With increasing confining pressure, elastic modulus, compressive strength, and shear strength, the kinetic energy dissipation of the drill string exhibits a pronounced decreasing trend. Within the investigated parameter ranges, the results indicate that the deformation resistance and failure resistance of the surrounding rock are the primary factors affecting drill-string kinetic energy dissipation. Specifically, the internal friction angle, confining pressure, elastic modulus, compressive strength, and shear strength have significant effects on the dissipation behavior. This study helps clarify the local kinetic energy dissipation of the drill string and provides a reference for evaluating energy transmission efficiency in underground rotary drilling.