Theoretical and numerical analysis of the rock breaking process by impact hammer

Hydraulic impact hammers used for rock breaking play a crucial role in the mining industries, but their operation is complex and inefficient. To address these challenges, this paper investigates the rock breaking process of impact hammers. Utilizing stress wave theory, a mathematical model for impact rock breaking is established, and the size of broken rock is estimated. Subsequently, the DEM-based numerical analysis verifies the reliability of the mathematical model and elucidates the working mechanism of impact rock breaking. Additionally, the study explores the influence of different hammer parameters on the rock breaking performance. The results indicate that the essence of rock breaking lies in the formation of a rock crushed zone and the initiation and growth of cracks under the impact load , with the main macrocrack extending towards the free surface closer to the operating point. Regarding rock breaking efficiency, the impact velocity has a relatively minor influence, while the drill rod diameter shows a positive correlation with efficiency. The drill bit angle significantly affects the rock breaking efficiency and is accompanied by changes in the rock breaking pattern. • A theoretical model of the rock breaking process under impact is established. • DEM simulation reveals the rock breaking mechanism with impact hammer. • The effect law and significance of operation parameters are obtained.