Dynamic force-penetration curves in rock by matching theoretical to experimental wave propagation response

A methodology to obtain the dynamic force penetration curve of a rock specimen is presented. For this, a simple portable experimental setup is used. On one end, a hand-held hammer strikes a slender chisel. On the other end, the chisel is in contact with the rock specimen into which the generated stress wave propagates. Strain gages installed at a selected section of the chisel are recorded throughout the impact duration. The theoretical signal at the same section is simulated using a numerical method based on the impulse momentum principle previously developed by the author. Essentially the shape of the simulated theoretical response at the strain gage section depends on the impact velocity of the hammer and the slope of the assumed force-penetration curve. These two parameters are adjusted until the shape of the theoretical signal at the strain gage closely matches the experimental signal. Due to its simplicity, the proposed methodology has the potential of becoming a standard dynamic test for obtaining the force-penetration curves in rocks.