Quantification of Rock Strength Using the Mechanical Drilling Parameters

The estimation of rock strength is most often required for the preliminary stage of rock engineering projects. The determination of rock strength properties in the laboratory is reliable, but the availability of a number of fine quality core samples for lab testing is very difficult. In this study, an attempt is made to investigate the usability of variations of thrust developed at the rock-bit interface and vibration frequency generated in the drilling machine head for estimation of rock strength during the rotary drilling. The variation of thrust and vibration frequency during drilling is measured using sophisticated digital type drilling dynamometer and data acquisition system (DAQ) with accelerometer sensor respectively. The second order regression models were developed to predict the rock strength such as uniaxial compressive strength considering the machine operating parameters and measured variables. The evaluation of the prediction ability of the developed models was checked using the three performance indices known as VAF, RMSE, and MAPE. The results revealed that the approached method is highly efficient for estimation of rock strength during rotary drilling.