Effects of Working Angle on Pneumatic Down-the-hole Hammer Drilling

The effects of the wor king angle on pneumatic down-the-hole (DTH) hammer drilling was investigated since these hammers were developed for vertical drilling and their performances in inclined positions need to be tested. The investigation begins by establishing a calculation model with which to simulate the percussive drilling of the hammer. The model consists of two parts. The first gives the kinetic energy of the piston at impact by simulating the thermodynamic cycle of the DTH hammer, and the second simulates the percussive drilling process according to the analyses of stress-wave propagation. In the meantime, a laboratory-scale test device was made for multi-angle hammer drilling tests. This device is based on a small pneumatic DTH hammer used in deep well drilling. By analyzing the force acting on the rock during impact at different angles, the percussive drilling process is carefully examined. Theoretical predictions and experimental results appear in fairly good agreement. The hammer's working performance in inclined positions can be obtained directly using the proposed model. Furthermore, when detailed evaluation is required, the hammer can be tested using the method proposed in this paper.