An experimental investigation into the drilling and physico-mechanical properties of a rock-like brittle material

Energy efficiency (specific energy) and penetration rate in rock drilling processes are dependent on various operational variables (applied load, torque etc.) in addition to the physico-mechanical properties of the rock being drilled. Experimental work, using a laboratory drilling setup, was carried out to investigate the interplay between the various operational variables and the physico-mechanical properties of cement mortar, an analogue for natural rock. Unconfined Compressive Strength (UCS) tests were first performed to characterise the cement mortar. The penetration rate and specific energy were determined for various experimental drilling scenarios and correlated with the operational variables employed for these drilling scenarios and the physico-mechanical properties of the cement mortar used. The results of the experimental work demonstrate the significance of applied load and torque for both penetration rate and specific energy in drilling. Additionally, the experimental results emphasise the influence of material (rock or cement) properties on the penetration rate and specific energy in drilling. From the testing data, empirical relationships are proposed for the purpose of determination of both penetration rate and specific energy for certain operational variables, and for given UCS of the material to be drilled.