Surface Morphology of Pre-Split Fractures in Plexiglas Models


The systematic examination of the topography of fracture surfaces, commonly referred to as fractography, has been widely applied to the investigation of fracture mechanics in metals, alloys, plastics and ceramics. Fractography can be useful in the analysis of the mechanics of dynamic fracturing in rock to explain a number of experimental facts for which theory is still contradictory. This paper summarizes an analysis of fracture surfaces produced between boreholes blasted simultaneously in three-dimensional Plexiglas models. The general appearance of fracture patterns in a row of boreholes blasted in a simulated infinite medium is analyzed and compared. Detailed visual examination by the naked eye and through optical and scanning electron microscopes reveals that characteristic morphological features in each case are well delineated. The effect of changing the experimental conditions of hole spacing and ecoupling ratio on (i) the fracture surface morphology, (ii) the point of crack initiation, and (iii) crack propagation, has been studied. When boreholes are spaced at less than a critical distance, crack initiation occurs at the midpoint between holes and is probably due to shock wave interaction. At distances greater than this critical distance, the crack initiates at the boreholes and is probably due to the wedging action of gas expansion. In the observed models, this critical distance was less than the optimum calculated for efficient explosive use. © 1977.


Mining Engineering

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Article - Journal

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© 1977 Elsevier, All rights reserved.

Publication Date

01 Jan 1977