2023 Volume 72 Issue 5 Pages 369-375
Rock drills have been widely used for blast hole drilling in tunnel construction and ore extraction. For the advancement of performance and efficiency of rock drills, it is essential to understand the penetration behavior of a button bit and each of the button tips into rock. In this study, static penetration tests were conducted with three rocks using each of button tips with six diameters. The test results showed that the force-penetration curves are linear in the loading phase and convex downward in the unloading phase for sandstone and andesite and that the curves are convex downward in both the loading and unloading phases for granite, if rock chipping does not occur. The force-penetration curves in the loading phase and deformation mechanisms of the rocks could be explained with the contact mechanics; plastic deformation is dominant for sandstone and andesite, and in contrast elastic deformation is dominant for granite. In addition, the relations of the diameter of a button tip, the Young’s modulus and yield stress of rock to the force-penetration curves were clarified. These results indicate that force-penetration curves are estimated beforehand from mechanical properties of the target rock. Occurrence of rock chipping was found to be influenced by not only the diameter of a button tip but also the heterogeneity of rock texture.
