Effect of strain rate on specific fracture energy and micro-fracture surface properties of rock specimen under dynamic uniaxial compression

Abstract

Effects of strain rate on specific fracture energy and micro-fracture surface properties of rock specimen were investigated at strain rates of ∼ 60–115.0 s-1. To achieve this, rock breakage was conducted under dynamic uniaxial compression using the split Hopkinson’s pressure bar. The fracture surface area of fine fragments (<8*10-3m) were measured using gas absorption method while the fracture surface area of large fragments (>8*10-3m) were measured using close-range photogrammetry. Results reveal that fracture surface area and specific fracture energy generally increase with strain rate during rock breakage under dynamic uniaxial compression. Similarly, the total fracture surface area of broken fragments also increased with dissipated energy. Results from scanning electron microscopy showed that fracture surface roughness and macro-crack abundance also increased with strain rate. Following energy requirement for rock breakage into size specifications for engineering applications, strain rate provides a reliable parameter for estimating specific fracture energy and fracture surface area at the forementioned strain rates. Accordingly, optimizing rock breakage processes using strain rate could reduce ore loss and energy wastage associated with production of unwanted fracture surfaces during rock breakage.