ANALYSIS OF DRILL HOLE CUTTINGS AND ROCK MASS PROPERTIES FOR PREDICTION OF MECHANICAL BREAKAGE PERFORMANCE

Abstract

Size distribution of blast-hole drill cuttings and rock mass properties were investigated to predict mechanical breakage performance. This research was embarked upon in order to establish a prediction criterion for determining rock resistant variations in strength to mechanical performance. Blast-hole cuttings were obtained from the blast-holes drilled and size distributions of the cuttings were determined. In addition, top-hammer drill with 38mm diameter was employed at two quarries for rock drilling. Rock samples from two operating quarries in Ikpeshi, Edo State, Nigeria were tested for Uniaxial Compressive Strength, Point Load Strength and Rebound Hardness using 1100 kN compression machine and Schmidt hammer respectively. The values measured in HNF/Fanalou Quarry and Golden Girl Quarry for Uniaxial compressive strength, Point Load Strength and Rebound Hardness were: 44.39 MPa, 5.77 MPa, 34.7 and 46.95 MPa, 7.46 MPa, 39.7 respectively. The number of blast holes drilled, depth and duration were obtained; these data were used to evaluate average penetration rate of drill. Mineral composition was determined by method of modal analysis. The result of size distribution analyses of the drill cuttings of the weight retained on 1700 μm, 212 μm and 75 μm sieve sizes varied from 36 - 96 g, 36 - 65 g and 73 - 98 g respectively for HNF/Fanalou. The size distribution of the blast-hole cuttings of the weight retained on 1700 μm, 212 μm and 75 μm sieve sizes varied from 16-80 g, 36-65 g, and 70-96 g respectively for Golden Girl Quarry. The percentage of calcites and dolomites contained in the rocks were 36.3 %, 63.8 % and 10 %, 89.4 % for HNF/Fanalou and Golden Girl respectively. The average penetration rates varied from 9.63 – 15.47 m/min and 10.36 – 15.77 m/min for both quarries at drilling length of 3,810 m and 3,429 m respectively. The breakage performance of the drill was better when drilling on rocks at Fanalou quarry and bit stalling that occurred at the two locations may be due to variation in rock strengths and discontinuities nature of rocks at different locations on the earth crust. The performance of drilling to penetrations differs in many rocks, therefore this justified the basis for the conduct of this research to compare and analyze drill hole cuttings and evaluate the rock properties in relation to mechanical parameters of drilling