Analysis of impact hammer rebound to estimate rock drillability

In this paper, the piston rebound common to both the Schmidt Impact Hammer and downhole hammer drills has been analyzed and calculated by means of str ess wave theory and the energy conservation law. A quantitative relationshi p between the amount of rebound of the piston and the impact resistance ind ex, or hardness of the rock, has been established. Those analytical results will not only be of benefit in acquiring a deep understanding of the usabl e range and condition of the Schmidt Impact Hammer, but also provide a defi nite answer to the feasibility of using the hammer rebound in drills with d own-hole hammer tool to carry out a real time measurement of the nature of the formation under the bit.