A laboratory study of rock properties affecting the penetration rate of pneumatic top hammer drills

Having collected rock samples from eight mines and one high way slope, the researchers did some tests on the samples to determine dry density, Uniaxial Compressive Strength, tensile Strength (Brazilian Test), elastic modulus, Schmidt hammer rebound number. In addition, a thin section of each rock was studied to calculate the mean size of rock grains, quartz content, hardness and abrasivity. The rock samples were finally drilled using an actual pneumatic top hammer drilling machine with a 3½ inche diameter cross type bit. Regression analyses showed that Brazilian tensile strength (R2=0.81), uniaxial compressive strength (R2=0.77) and Schmidt hammer rebound (R2=0.73) have the most significant effect on drilling rate and have a relatively appropriate correlation with drilling rate.

Keywords:

Drillability , rock material , physical and mechanical properties , pneumatic top hammer drills