The relationship between textural properties of selected Nigeria rocks and penetration rate of top-hole hammer drill was investigated. These rock samples were tested in the laboratory for mineral composition, silica content and porosity. Also, average grain size and packing density were determined from photomicrograph of the samples using empirical equations proposed by researchers. Penetration rate for each rock samples obtained in the field were correlated with the textural properties to establish their relationships.The results show that all textural character and penetration rate have high coefficient of correlation for all the samples. The highest penetration rate was experience on biotite hornblende-granite having mean packing density of 92.58% and the silica content vary for 82. 60 -82.72%. This has revealed that penetration rate of rock drill bit in quarries is related to textural rock properties and this will be necessary to have overview of time of drilling as well as rock response to mechanical loading.

This work deals with the investigation of physical and mechanical properties of selected rocks for condition of drilling categorization. Rock samples collected from five drilling locations were tested in the laboratory for uniaxial compressive strength, tensile strength, and Drilling Rate Index (DRI) using 1,100 kN compression machine, point load tester and miniature drill. Similarly, hardness, brittleness, Rock Abrasivity Index (RAI), penetration rate and bit wear rate were determined. The results showed that uniaxial compressive strength, tensile strength and Drilling Rate Index varied from 47.78 - 111.11 MPa, 8.09 - 19.44 MPa, and 20 - 52 respectively. The Nast point system chart was used to classify the rocks into drilling conditions. The drilling classification shows that the drilling condition of the rocks varied from slow to fast. The drillability characteristics of the rocks vary from extremely low to medium as specified by the Drilling rate Index (DRI). It was concluded that uniaxial compressive strength, texture and grain size, drilling rate index and Equivalent Quartz Content (EQC) are important parameters affecting drilling condition of the rocks.

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This study examines the characteristics of limestone formation as well as the performance of different tri-cone bits in limestone in Ewekoro. Rock samples were collected from different layers of limestone encountered in the quarry during drilling operation. These samples were tested in the laboratory for uniaxial compressive strength and the tensile strength. Also, the chemical compositions of the samples were determined using the X-Ray Fluorescence (XRF) Spectrometer and the results were used in the determination of the Equivalent Quartz Content (EQC). The length of the insert buttons on the surface of the drill bits were measured using digital vernier calliper at regular intervals. In addition, the tooth and bearing wear rates as well as the penetration rate were determined on the field. The results of the uniaxial compressive strength varied from 86.5MPa (medium strength) to 112 MPa (high strength). The Equivalent Quartz Content (EQC) of the rock samples varied from 17.37% to 36.676% while the Rock Abrasivity Index (RAI) varied from 15.03 to 43.317. The results of the drilling variables showed that higher wear rate was experienced when milled tooth tri-cone bit was used for drilling than using insert tri-cone bit for drilling limestone formation, hence the tri-cone bits performed optimally well in all the formations except in glauconite (GLAB) where its performance was low. However, the economic analysis indicated that the insert tri-cone bit drilling cost per metre varied from N660/m to N673/m while the milled tooth tri-cone bit drilling cost per metre varied from N684/m to N710/m. This will act as a data base for selection of drill bits and drilling equipment in limestone quarries.

This work was carried out to determine the influence of rock properties and drilling machine parameters on the penetration rate at the SJ pit of Rössing Uranium Mine, Namibia. Rock properties (uniaxial compressive strength, tensile strength, and modulus of elasticity) of samples collected were determined in the laboratory. Drilling experiments were conducted in which feed pressure, air pressure, rotary speed, weight on the bit, and torque were varied to measure their effect on the penetration rate. The uniaxial compressive strength varied from 90-180 MPa for layered marble-quartzite and banded gneiss. Increases in feed pressure, weight on the bit, and rotary speed beyond the optimum level led to a decrease in penetration rate and caused the drill bit to 'stall'. Results of the study revealed that penetration rate increases with an increase in the feed pressure and air pressure. After reaching a maximum value, the penetration rate begins to decrease despite increasing feed pressure. A very high torque causes the drill bit to stall, since the feed pressure is too high and the air pressure is not sufficient to remove the cuttings from blast-hole at maxium bailing velocities. The average penetration rate varied from 19 to 45 m/h for phase 2 of the pit, and from 17 to 68 m/h for phase 3. The optimum drilling machine parameters obtained in phase 2 and phase 3 were slightly lower than those currently being used at the mine. The trials of the optimum machine parameters will assist in reducing the cost of drilling, which varied from N$29.48 to N$36.31 per metre for the tricone bit.