The influences of drilling parameters on the rate of penetration in rock rotary-percussive drilling process

The rotary-percussive drilling is commonly-used for geotechnical investigation. The rate of penetration (ROP) is critical to the construction period of geological drilling, and the setting of drilling parameters directly affects ROP. To clarify the influence of drilling parameters on ROP, laboratory full-scale rock drilling tests were conducted for three types of rocks (gneiss, dolomite, and marble). The drilling data were recorded in real time. Through the correlation analysis, the mutual independence of drilling parameters (feeder pressure, hammer pressure, and revolution per minute) was demonstrated. Then, the relationships between ROP and drilling parameters were presented. Afterwards, the influencing weights of drilling parameters were calculated by the entropy weighting method. The results indicate that the ROP variations show similar trends in three different types of rocks. ROP rises with the feeder pressure increasing from 5.5 MPa to 8.5 MPa. ROP grows at first but then declines with the hammer pressure increasing from 14.5 MPa to 18 MPa. ROP remains constant with the rotary speed increasing from 180 rev/min to 280 rev/min. The weight proportions of the three parameters on ROP are that the hammer pressure is the highest, followed by the feeder pressure, and the rotation speed is the lowest.