Rock hardness is an important indicator reflecting the relative hardness

drillability

and blastability of rock formation. Accurate interpretation of the response of percussion drilling tools can provide new possibilities for in-situ

rapid

and quantitative evaluation of rock hardness. High-precision digital displacement

hydraulic pressure

and rotational speed sensors were used to monitor the key transmission parts of the percussion drill

and a digital monitoring system for the drilling process was then established. Rock hardness measurement and orthogonal tests of percussion drilling were parallelly carried out

and a standard database containing response data of the drill when drilling various types of rocks was established. Functional relationships between propelling pressure

percussion pressure

rotational speed

and impact energy dissipation were developed

and a novel method to quantitatively evaluate rock hardness based on impact energy dissipation index was proposed. The performed tests and analyses revealed that there is an inverse linear relationship between the propelling pressure and impact energy dissipation. The fitting curve of percussion pressure and drilling energy dissipation is an open upward parabola

and the curves for various rocks have the same symmetry axis but different curvature radii. The influence of rotational speed of drill rod on drilling energy dissipation is negligible. By dimensionless treatment of drilling energy dissipation per unit volume

the influence of mechanical parameters of percussion drilling is removed

and the impact energy dissipation index 

which has low discreteness and a good correlation with rock hardness

was defined to characterize the rock hardness. The response data of the drilling process in conventional boreholes were obtained and interpreted by the digital sensing technology

and the obtained data were used to determine the rock hardness without additional survey or test

which puts forward a new way for direct evaluation of rock mass parameters on engineering sites.