Sensitivity analysis of drilling parameters in rock rotary drilling process based on orthogonal test method

Drilling exploration is the main method for geological studies of rocks and soil. Selecting reasonable drilling parameters is important for ensuring the safety and economic benefits of a project. According to the force limit equilibrium of rock during rotary drilling and using the energy equilibrium method, the relationship between the vertical drilling efficiency eta and drilling parameters such as the speed of rotation, thrust force, and rotation torque were deduced in this study. Through improvements in the drilling process monitoring (DPM) system, it was possible to quickly, efficiently, and quantitatively obtain the drilling parameters during rock drilling. An in situ drilling WA of granite using the improved DPM system showed the sensitivity of the drilling efficiency to each drilling parameter via an orthogonal test. The results indicated that the optimal drilling efficiency (eta = 13.2%) was achieved under the following WA conditions: A rotation speed of 128 r/min, thrust force of 788 kPa, and a rotation torque of 64 N.m. the influence of the thrust force on the drilling efficiency was extremely significant, the sensitivity of this parameter was high, and the weight value of the thrust force had a 57.87% influence among the others. Furthermore, the influence of the rotation torque on the drilling efficiency index was significant, the sensitivity to this parameter was neither high nor low, and its weight value was 36.82%. In contrast, the influence of the rotation speed on the index was insignificant, sensitivity to this parameter was low, and its weight value was 5.31%. The research methods and results presented herein can serve as references for the optimum design of drilling construction and the reasonable selection of drilling parameters.