ORIGINAL PAPER Rock strength characterization using measurement while drilling technique C. R. Lakshminarayana 1 • Anup K. Tripathi 1 • Samir K. Pal 2 Received: 23 October 2019 / Accepted: 27 May 2020 Ó Indian Geotechnical Society 2020 Abstract The approximation of strength properties of rocks most often requires during the preliminary phase of any engineering projects related to rock mechanics. The main disadvantage of evaluating the rock properties in a testing laboratory is the prerequisite for high-quality rock core with many numbers. In this empirical method, the essential strength properties of rocks would measure during the rock drilling process using some identified machine variables along with the acoustic parameter. The machine operating variables such as thrust and torque and acoustic vibration parameter collecting at the machine head were used to develop rock strength models. A drill-type dynamometer was employed to gauge the machine vari- ables and the NI-9234 data acquisition system for gauging the vibration parameter. The evaluation of the mathemati- cal models for their efficiency shows that the applied empirical approach could determine the strength properties with fewer errors and can use as an alternative method for measuring the compressive and tensile strength of sedi- mentary rocks in the laboratory without using core samples. Keywords Compressive strength Á Tensile strength Á Weight on bit Á Torque Á Statistical model Introduction Rock drilling is the essential activity to be carried out in many engineering projects such as mining, petroleum, and civil. While carrying out these projects, the mechanical properties of rocks are often crucial information to be calculated. The removal of rock cores needed for a labo- ratory test is expensive. Also, removing the cores every time from the weathered and highly fractured nature rocks like the sedimentary type is impossible. The process of making ready the sample for laboratory tests is somewhat tedious and costly. Therefore, the sedimentary rocks may not quantify correctly, and their properties are decided on the small accessible rock samples. At last, the intact rock is characterized dependent on the results gathering with a small number of samples. This evaluating system may not bring correct end results particularly in case of the rock properties which are influenced by the difference in wet- ness or percentage of water content. In this way, to dispose of this issue, the specialists and geologists have discovered an optional method for estimation or characterization of rocks by employing the experimental predictive models. In recent times, many investigators endeavored to evaluate the rock properties while drilling process and the final result was satisfactory with fewer errors. During the rock drilling process, the machine operating conditions, along with the acoustic parameters, are utilized in numerous examinations to evaluate the rock properties. Basarir et al. [1] experimented with approximating the uniaxial com- pressive strength (UCS) using the diamond core drilling parameters. From the obtained data and its analysis, it was revealed that the drill bit’s penetration rate (PR) is the fundamental variable affecting the rock strength with the remarkable coefficient of determination (r 2 ). Likewise, the thrust was the following machine operating parameter & C. R. Lakshminarayana crlaks042@gmail.com 1 Department of Mining Engineering, N.I.T.K, Surathkal, Karnataka 575025, India 2 Department of Mining Engineering, IIT, Kharagpur, West Bengal 721302, India 123 Indian Geotech J https://doi.org/10.1007/s40098-020-00441-3