Efficiency evaluation of a percussive drill rig using rate-energy ratio based on rock drilling tests

The drilling efficiency of a percussive drill rig which is widely used in rock engineering attracts great attention. The goal of a higher drilling rate and lower specific energy is pursued in the rapid and economical construction of projects. This study aims at clarifying the influence of drilling parameters on the drilling efficiency. To explore the variations of the drilling parameters, drilling tests were conducted for a rock block. Based on the drilling data, relationships between the drilling rate and the drilling parameters (the percussive pressure, the propelling pressure, and the rotary speed) were found. Besides, a specific energy model for the percussive drill rig was established through the theoretical analysis, and the specific energy was calculated by the drilling data. Furthermore, a rate-energy ratio was proposed to evaluate the drilling efficiency by coupling the drilling rate and the specific energy. Afterward, the influence of the drilling parameters on the rate-energy ratio was discussed. The results show that the main factors affecting the drilling rate are the propelling pressure and the percussive pressure. The specific energy for breaking the rock mainly comes from the impact energy. To increase the drilling efficiency, the propelling pressure should be set maximally in its reasonable threshold but the percussive pressure is not the higher the better. • Large-scale laboratory experiments were conducted to explore the relationships between drilling parameters and the drilling rate. • The variations of the drilling rate versus the percussive pressure, the propelling pressure, and the rotary speed were found. • A specific energy model for the percussive drill rig was established based on the theoretical analysis. • A rate-energy ratio was proposed to evaluate the drilling efficiency.