Estimation of Specific Energy in Rock Indentation Test

Static indentation tests were carried out in six types of rocks namely pink marble, limestone, basalt, steel gray granite, moon white granite and black galaxy granite using commercial drill bits (Cross bits) of 35, 38, 45, 48mm diametersat a loading rate of 0.1 kN/sec on Microcontroller compression testing machine (with fabrication work to hold the indenter). The tests were conducted on rocks at index angles of 100, 200, 300, 400. The objective is to estimate the specific energy (energy necessary to excavate a unit volume of rock) during indentation and to study the influence of index angle on specific energy. From the experimental data, Force-Penetration (F-P) curves were plotted and specific energy values were calculated from F-P curves for each bit rock combinations. The optimum specific energy is at 30° index angle for the soft rocks (pink marble, limestone) whereas; the optimum specific energy is at 20° index angle for the rocks (basalt, steel gray granite, moon white granite and black galaxy granite).