Sensitivity investigation of drilling efficiency to operational parameters of a drifter

Drilling operations are extensively used for underground excavation, and their efficiency has a direct impact on project duration and expenses. Adjusting the operational parameters during the drilling process is important for improving drilling efficiency. In this study, the sensitivity of drilling efficiency to operational parameters was investigated. Full-scale drilling tests for a dolomite block were conducted using a hydraulic drifter, and the Measurement While Drilling system was used to record the drilling data. Orthogonal schemes were designed to arrange the tests, and the penetration rate, specific energy, and rate-energy ratio were regarded as evaluation indices to assess the drilling efficiency. The sensitivity of the evaluation indices to operational parameters was analysed using both range analysis and variance analysis. Results show that the optimal combination of parameters within the test range was determined to be the propelling pressure of 8.5 MPa, percussive pressure of 17.5 MPa, and rotary speed of 250 rev/min to obtain the maximum drilling efficiency. The sensitivity sequence of the rate-energy ratio was propelling pressure, percussive pressure, and rotary speed, with weights of 54.0, 38.7, and 7.3%, respectively. These findings can provide a valuable reference for adjusting the operational parameters of hydraulic drifters to optimise drilling efficiency.