Studying the effects of borehole length on the impact drilling speed in different rocks

The performed tests in this work include a wide range of rock masses of the Kopaonik massive of different strength (f = 2.3 - 16). Drilling was done with drill hammers VK-24 and RK-21 at optimum sharpening angle with different drill rod lengths (0.8, 1.2, 1.6, 2.4 and 3.2). Compressed air pressure is 0.60 MPa and diameter of drilling chisel d = 32 mm. The obtained results and analysis indicate that it is possible to determine the interdependence between the borehole length and drilling speed. The results of these tests are shown in Tables 1, 2, 3 and 4 and diagrams 1, 2, 3 and 4.