Study of Factors Controlling Penetration Rate in Percussive Top Hammer Drills

Different factors control penetration rate, which is an influencing part of drillability. To study penetration rate it is recommended to record and analyze the effect of one or two variables, while keeping others constant. In this study, 81 data of penetration rate from 12 drill rigs, 14 data of two Robolt rigs, and data gathered by their manufacturers, from a dam site, were analyzed to check the role of influencing parameters of equipments. Rock type of the study area is Bakhtiari conglomerate and is constant for all the studied samples. Diameter of the bit and impact power of the rig are two main influencing factors, but with different level of consequences. The effect of rig’s impact power is so pronounced that change of rig or rock type cannot highly diminish its role. Changing the bit type, from ballistic to spherical, have not the same effect on penetration rate and it is related to the type and design of the hammer.