Faculty Publications
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Item MWD technique to estimate the uniaxial compressive strength of rocks(American Institute of Physics Inc. subs@aip.org, 2020) Lakshminarayana, C.R.; Tripathi, A.K.; Pal, S.K.The measurement of mechanical properties of rocks is an essential task to be carried out during the projects involving the rock engineering activities such as civil constructions, tunneling, excavations etc. Although the quantification of uniaxial compressive strength in the laboratory is much faithful, the availability of rock samples and their preparation according to ISRM standards is the major limitation. In this experimental investigation, the quantification of the uniaxial compressive strength (UCS) of rocks using the measurement while drilling (MWD) technique was attempted. During the drilling of dissimilar strength rocks for various combinations of drilling operational parameters, the value of thrust and torque were collected using the digital type drilling dynamometer. The prediction of the UCS was performed by developing a mathematical model considering the parameters used for operating the machine and corresponding thrust and torque values. The prediction capacity of developed model was evaluated using the value account for (VAF), root mean square error (RMSE) and mean absolute percentage error (MAPE). From the results it was concluded that the MWD technique could be a prominent tool for estimation of rock strength properties in future. © 2020 Author(s).Item Quantification of Rock Strength Using the Mechanical Drilling Parameters(Springer Nature, 2020) Lakshminarayana, C.R.; Tripathi, A.K.; Pal, S.K.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. © 2020, Springer Nature Switzerland AG.Item Prediction of physico-mechanical properties of rocks using dominant frequency of vibration during rotary drilling(Science Publishing Corporation Inc ijet@sciencepubco.com, 2018) Lakshminarayana, C.R.; Tripathi, A.K.; Pal, S.K.In this study, an attempt is made to estimate some of the important physico-mechanical properties of sedimentary rocks using second-order multiple regression mathematical models. For model development, different drilling operational parameters and equivalent dominant frequencies of vibration excited at spindle head during rotary drilling were used. The prediction capacity or performance of the developed models was evaluated by using variance account for (VAF), root mean square error (RMSE) and mean absolute percentage error (MAPE).In addition, the strength of the relationship between measured and predicted value of rock properties are also checked using the Pearson correlation coefficient. Prediction performance indicators and correlation coefficients showed that the prediction model developed through the approached method can be successfully used for preliminary investigation of physico-mechanical properties of rocks which are often used as a primary data for the design of mining and civil engineering projects. © 2018Lakshminarayana C. R et. al.Item Estimation of Rock Strength Properties Using Selected Mechanical Parameters Obtained During the Rotary Drilling(Springer, 2019) Lakshminarayana, C.R.; Tripathi, A.K.; Pal, S.K.During the preliminary stage of rock engineering projects, the estimation of mechanical properties of rocks is most often required. The requirement of a large number of high-quality rock core samples is the major drawback when the mechanical rock properties are to be determined in a well-established rock mechanics laboratory. In this study, an attempt is made to estimate the uniaxial compressive strength and Brazilian tensile strength of sedimentary rocks using the selected mechanical drilling operating parameters obtained during the rotary drilling. The operating measured parameters such as the weight on bit or thrust and the vibration frequency induced at machine or drill head were acquired using the drill tool dynamometer and sound/vibration data acquisition system, respectively. The mathematical models were developed considering the drilling operational parameters (drill bit diameter, drill bit speed and penetration rate) and measured mechanical parameters (thrust and vibration frequency). The prediction potential of the developed models was assessed by the prediction performance indices. The outcome results revealed that the developed mathematical model using the approached method is significant and can be conveniently used for the estimation of mechanical properties of rocks during the rotary drilling. © 2019, The Institution of Engineers (India).Item Prediction of Mechanical Properties of Sedimentary Type Rocks Using Rotary Drilling Parameters(Springer, 2020) Lakshminarayana, C.R.; Tripathi, A.K.; Pal, S.K.The estimation of strength properties of sedimentary rocks is most often needed during the preliminary phase of many rock engineering projects carrying out in sedimentary regions. The main drawback of determining the rock properties in a test center is the requirement of the number of superior quality rock core specimens. In this experimental investigation, the uniaxial compressive strength (UCS) and tensile strength of sedimentary rocks are estimating using well-identified drilling variables and acoustic parameters obtained during the rotary type rock drilling. The drilling variables such as thrust, torque, and vibration parameters are used to develop the mathematical models of strength properties of rock. A drill type dynamometer was used to measure the drilling variables, and the vibration parameter would measure using the NI-9234 data acquisition system. The prediction efficiency of the mathematical model is evaluating using performance indices. Results show that the used experimental method can estimate the considered responses (UCS and tensile strength) with the acceptable percentage errors of 10.52% and 11.27% respectively, and may be useful to measure the UCS and BTS of sedimentary rocks in a laboratory capacity without test core samples. © 2020, Springer Nature Switzerland AG.Item Rock strength characterization using measurement while drilling technique(Springer, 2020) Lakshminarayana, C.R.; Tripathi, A.K.; Pal, S.K.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 variables and the NI-9234 data acquisition system for gauging the vibration parameter. The evaluation of the mathematical 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 sedimentary rocks in the laboratory without using core samples. © 2020, Indian Geotechnical Society.Item Experimental investigation on potential use of drilling parameters to quantify rock strength(Springer, 2021) Lakshminarayana, C.R.; Tripathi, A.K.; Pal, S.K.The uniaxial compressive strength (UCS) represents the strength of the rock. It frequently requires during the introductory phase of mining projects such as tunneling, rock excavation, blast hole designs, etc. Usually, the determination of UCS of rocks is carrying out in a concerned laboratory. The main drawback of determining the UCS in a laboratory requires at least five core samples of high-grade quality. Many problems and limitations are associated with removing the core, and also preparing the test specimen for UCS is tedious, time-consuming, and expensive. Therefore an attempt is made to develop an efficient indirect method to estimate the UCS of rocks without using the core samples. In this experimental investigation, the drilling response, such as thrust, is gathered by drill tool dynamometer considering the different drill operating parameters. The prediction model is developed with a regression technique using the measured thrust and calculated torque. The prediction capacity and validation of the model are carried out using the standard procedure. The experimental results show that the model could explain the variance in UCS up to 93.60%. RMSE and MAPE values in terms of percentage are 3.49% and 11.27%, respectively. Besides, the model's validation is checked for sandstone and limestone having the UCS 28 MPa and 35 MPa, respectively, and yielded the best prediction results with an error of 8.51% and 8.01% suggesting that the developed model could predict the UCS of sedimentary rock types within acceptable error limit, and reasonably. The correlation of UCS of rocks and drilling specific energy is also tested and found that linear relationship between them with an R2 value of 92.10%. © 2021, The Author(s).