A theoretical and experimental study of the percussive drilling of rock part I—theory of percussive drilling

Abstract

The theoretical mechanics of the percussive drilling of rock are developed from analysis of stress-wave interactions in the drilling system. Particular attention is given to 1. (i) the efficiency of impact energy transfer from drill steel to rock, and 2. (ii) the minimum thrust force needed to ensure bit-rock contact at the beginning of each impact. A simple expression is derived from which the penetration rate of a percussion drill can be predicted, provided the amount of impact energy per unit volume of rock broken is known for the appropriate drill bit and rock type, together with certain and operational parameters of the drilling machine.