Prediction of rock hardness and drillability using acoustic emission signatures during indentation

Abstract

This paper reports rock indentation tests which indicated that there was a certain relation between the indentation hardness of rock and the AE parameters, such as accumulated number of events, peak RMS and integrated RMS. Among the above-mentioned AE parameters, the correlation of RMS of AE events with indentation hardness is pronounced and more than ever the integrated RMS is the best index to correlate with the indentation hardness of rock. It represents the sum of amplitudes of AE varied during all the indentation process and reflects the size of AE energy released in the time period of indentation. Indentation hardness corresponds well to peak RMS value for different rock types. The onset of significant AE activity appears at about 40% peak indentation load, and intense AE activity corresponding to fracture propagation and chipping initiates at about 80-90% of peak indentation load. The peak RMS and integrated RMS may be recommended as the indexes to express rock hardness and may be further employed to predict rock drillability using these indexes in association with penetration rate of drilling.